WO2011132205A2 - Process for creating earthquake disaster simulation in virtual reality environment - Google Patents
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Abstract
A computer-assisted method for creating earthquake engineering based realistic earthquake simulation in immersive virtual reality environment comprises: careful selection of building plan and internal elements on the basis of simulation objective, then selection of a suitable earthquake ground motion data from a pool of pre-recorded or synthetic earthquake data, then designing computer based structural engineering models of buildings and internal elements therein, thereafter, generating earthquake response of the said buildings and the said elements on the basis of earthquake engineering principles, then generating three dimensional (3D) computer models of the said buildings and the said elements and also mapping the said response onto these 3D models thereby producing 3D anirnations, thereafter creating stereoscopic visual and audio renderings of said animations for the immersive virtual reality platform of interest.
Description
Process for Creating Earthquake Disaster Simulation in Virtual Reality
Environment
Field of the invention
The present invention relates to disaster simulation system, more particularly, to a process for creating an earthquake disaster simulation in a virtual reality environment on the basis of earthquake engineering principles.
Background and prior art
Natural disasters, such as earthquakes occur after long intervals, but may be extremely devastating. Earthquakes cannot be predicted, so the only counter- measure against effects of the earthquake is to be better prepared for the same. The preparation can be through suitable response, search, and rescue system. Further, the preparation can also be through better training and sensitization of the people. There are several suggestions in the field of disaster management on improving safety against earthquakes.
It is in human nature that events and situations that have been experienced in the past are easier to remember in the future compared to merely reading or hearing about them. However, earthquakes cannot be created or experienced at will since it is a natural process. In a very limited way, its shaking can be simulated using suitable moving platforms technically known as shake tables.
However, there are limitations on the reality of simulations that are feasible through such means since an earthquake is likely to be experienced through shaking of the ground as well as that of the surroundings such as buildings, its contents and the like therein.
While the shake table can be given motions, it is very difficult, expensive and cumbersome to create structure and content models on shake tables. Even if these
are created, they are likely to be damaged by a single shaking and will not be reusable. From these considerations, a computer based earthquake simulation system that realistically portrays the behaviour of the desired physical environment during an earthquake can be a very effective tool.
Virtual reality is one such field which allows recreating an experience with high fidelity and repeatability and hence a choice of technology for the solution of the problem mentioned above. On these lines, Immersive virtual reality platforms can be utilized to create an earthquake simulation where user can be sensitized against earthquake effects repeatedly and in a hazard free manner. However, such a method to realistically create an earthquake on virtual reality platforms has not been proposed or patented in the past.
Ref 1 . Carolina Cruz-Neira, Daniel J. Sandin, Thomas A. DeFanti, Robert V. Kenyon and John C. Hart. "The CAVE: Audio Visual Experience Automatic Virtual Environment", Communications of the ACM, vol. 35(6),
1992, pp. 64-72. DOI: 10.1 145/129888.129892.
Ref 2. Carolina Cruz-Neira, Daniel J. Sandin and Thomas A. DeFanti.
"Surround -Screen Projection-based Virtual Reality: The Design and Implementation of the CAVE", SIGGRAPH'93: Proceedings of the 20th Annual Conference on Computer Graphics and Interactive Techniques,
1993, pp. 135-142, DOh l O.l 145/1661 17.166134.
Computer Aided Visualization Environment abbreviated as CAVE™ (as described in Ref 1 and Ref 2) or CAVE-like environments can be utilized as the choice of immersive virtual environment in which earthquake simulation can be experienced. The CAVE™ is a room whose walls, ceilings and floors surround a viewer with the projected images on them. Viewing is accomplished through special glasses which help the viewer to experience stereographic images synchronously. This creates a sense of depth and immersion in the mind of the viewer. The room is also equipped with the multichannel surround sound system. Along with the visual presentation accompanied audio can be presented to the viewer using this sound system. Overall
this creates a truly fantastic and highly realistic experience to the viewer. This system can be utilized as a virtual reality platform on which the proposed method can create the required earthquake simulation.
Further, US Patent No. 6, 154,723, dated November 28, 2000, describes a virtual reality 3D interface system for data creation, viewing and editing. The patent describes the hardware of 3D virtual reality creation, manipulation and editing system including a voice and 3D gesture input interface, wherein a group of people can experience virtual reality at the same time. This system too can be utilized as a virtual reality platform on which the proposed method can create the required earthquake simulation.
US Patent No. US 6,563,489 B l , dated May 13, 2003, describes system for placing a subject into virtual reality. The system comprises a closed sphere shaped capsule defining a real environment. Any virtual environment can be created by virtual environment generating means and means for displaying the virtual environment to the user. Limitation of the system is that only one user at a time can use the system. This system too caii be utilized as a virtual reality platform on which the proposed method can create the required earthquake simulation.
US Patent No. US 6,701 ,281 B2, dated March 2, 2004, describes a method and apparatus for analyzing building performance. The patent also describes evaluation methodology to determine consequences of fire or other natural hazard on building. Performance of a building is computed using a response function defining a response of a building to specific environmental change, e.g. occurrence of a fire. 3D simulation images of the building structure, of the building response and of individual's refuge motion are computed. The main objective of this patent is to facilitate analysis of building performance.
Limitation of the patent is that it aims at analysis of building performance and using the simulation results to improve the building design. It is not related to the disaster simulation of earthquakes or similar scenarios where the recreation is aimed at
providing insights and sensitization to the users against such scenarios. The patent also does not aim for realistic or physically based recreation of the earthquake scenario. Further the patent does not cover non-linear structural behaviour and modelling of phenomenon like crack formation, damage/collapse etc during the course of an earthquake.
US Patent No. US 6,774,885 B l, dated August 10, 2004, describes a system for dynamic registration, evaluation, and correction of functional human behaviour. The patent describes a real-time motion tracking and feedback technology using virtual reality and physical motions. Motion capture technology and a motion platform with runtime interaction in a real time feedback loop to provide a physical and virtual environment. Such interactive systems can be used in the present invention for registering interaction between the users and the objects under simulation.
Accordingly, looking at the cited prior art it is clear that a process for creating earthquake or any other disaster simulations in immersive virtual environments has not been described previously.
Summary of Embodiments
In an aspect of the invention, a computer assisted method for use in conjunction with a virtual reality platform comprises; planning the earthquake scenario based on the insightful knowledge of disaster training and earthquake engineering, then selecting analytically, a set of suitable earthquake disturbance data on the basis of simulation objectives, then creating structural models capable of linear and ηθη-linear analysis based on the knowledge of earthquake engineering and visualization objective, then carrying out computer assisted numerical simulations to generate response time history for the scenario objects, then creating 3D computer graphics models of the scenario objects and mapping the estimated time history responses onto these models thereby generating 3D animations depicting the exact things happening around in the scenario during the course of the earthquake, then rendering the said
animations for the virtual reality platform of interest along with the audio cues and cinematographic effects.
In another aspect of the invention, scenario objectives could be to sensitize people against effects of earthquakes, or to train participants for rescue missions, or to train engineers or architects for better planning the buildings and other objects to mitigate damages occurring due to the earthquake or similar disasters, or it could be any other objective which requires realistic simulation of the earthquake.
In another aspect of the invention, earthquake data is selected carefully and analytically to serve the purpose of fulfilling the simulation objective. Earthquake duration, intensity, frequency etc are all carefully selected with the knowledge of earthquake engineering and visualization requirements of the scenario.
In another aspect of the invention, structural models of the planned scenario objects are created. These models can simulate linear and/or non-linear response behaviour as required by the simulation. Apart from the earthquake engineering requirements, modelling is performed keeping into consideration the trade-offs and requirements of the visualization.
In another aspect of the invention, computer assisted linear and/or non-linear numerical analysis is performed to simulate the disturbances occurring in the scenario due to the earthquake motion. These include motion and distortion profiles of various scenario objects.
In another aspect of the invention, non-linear structural numerical analysis and heuristic based estimation is performed on the scenario objects to generate effects like crack, damage and/or collapse occurring during the course of the disaster. With the help of advanced knowledge in the field of earthquake engineering and insightful numerical analysis planning, characteristic parameters for the said effects are estimated. Characteristic parameters estimated for these effects are for predicting their shape, extent and/or evolution with time.
In another aspect of the invention, three dimensional (3D) computer graphics models of scenario objects are created with the help of the said structural models. Earthquake time history response and characteristic parameters for crack/damage effects are mapped onto these models to generate 3D animations. Other effects occurring during the earthquake such as dust-debris formation or puffs, smokes etc are visualized with a qualitative approach on the basis of generated earthquake response, and domain knowledge about the disaster.
In another aspect of the invention, sounds generated during the earthquake events are simulated spatially and qualitatively. A combination of recorded and synthetic sounds is used to create simulation sounds mimicking the real sounds occurring during such disasters.
In another aspect of the invention, the said 3D visual animations and the said sound animations are combined and rendered for the virtual reality platform of interest. Camera/observer location and motion is adjusted according to the path of the observer in the scenario and earthquake disturbance response at those specific locations. The rendering could be an offline or a real-time process based on the simulation requirements.
Brief description of the drawings
Figure-1 depicts the overview flow of the embodiment method of creating earthquake simulation, major process elements involved in the invention are described in short in accordance with the present invention;
Figure-2 depicts the process of creating structural engineering models capable of simulating linear and non-linear behaviour;
Figure-3 depicts the process of carrying out numerical simulation of linear structural models to generate earthquake time history response;
Figure-4A depicts the process of carrying numerical simulation of non-linear structural models to generate earthquake time history response;
Figure-4B depicts the process of estimating crack/damage characteristic parameters from the earthquake time history response generated from non-linear analysis;
Figure-5 depicts the examples of creating three dimensional (3D) computer models based on the structural engineering models of the object of interest;
Figure-6 describes the overview flow of how the earthquake response time history is mapped to 3D models to generate 3D animations;
Figure-7 depicts the flow of mapping the motion profiles in the time history response onto the corresponding 3D models;
Figrue-8 depicts how the crack and damage characteristic parameters are mapped onto the corresponding 3D models to visualize these effects; and
Figure-9 depicts major elements involved in the rendering of the said animations for the virtual reality platform of interest.
Description of Embodiments
References will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of the ordinary skills in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, circuits and network have not been described in detail so as to not unnecessarily obscure aspects of the embodiments.
The embodiment method of creating earthquake simulation is a process involving multidisciplinary and advanced skills. Civil engineering methods, earthquake engineering expertise, computer graphics knowledge and cinematographic skills are assembled in a unique way to create an asset in the field of disaster response and training. Virtual reality platform can be used very effectively to sensitize people against the effects of the earthquake and other disasters. The same could be used to train people on how to appropriately respond during such a calamity. The objective of such a simulation could even be to train engineers or architects to gain insights of such disasters and come up with better structural plans to mitigate organic and inorganic damages.
Referring now to figure 1, a flow chart of a process (1000) for creating earthquake simulation on a virtual reality platform is illustrated. The process ( 1000) starts at step (100).
At step (1 01 ), based on the simulation objective for the simulation, an appropriate building plan is first selected along with the details and arrangements of objects such as chairs, tables, chandeliers, photo-frames etc. In accordance with the scenario requirements, structural properties of the building are finalized such as material (masonry, steel, RCC etc), dimensions (height, length and width), plan (rectangular, circular, T-shaped, L-shaped or irregular) and elevation. Careful selection of internal elements is equally important as too much elements will clutter the internal space and may create traumatic effect. On the other hand too few elements may not create strong enough impression for long lasting memory. If the simulation objective requires an outside or open surrounding for the experience of an earthquake, other building structures and ambient environment plan must be selected as well.
Once a scenario plan is finalized, appropriate earthquake data needs to be selected at step (102). The earthquake ground motion data is available in the form of displacement/acceleration recorded at time interval of fraction of second to several seconds. In an embodiment, the earthquake ground motion data is pre-recorded
historic earthquake data. In another embodiment, earthquake ground motion data is a computer generated synthetic ground motion data. The earthquake ground motion data is selected by using structural analysis of the said scenario objects, requirements of the intended audience, site and location of the said buildings and/or any other specific simulation objective. Each earthquake has its own peculiar characteristic, such as duration, intensity, frequency and the like. Hence, it is extremely important to choose earthquake record that suits the requirement. Inappropriately chosen earthquake data cannot create the desired building response to meet the simulation objective. This earthquake data could be a scaled/modified version of one of the prerecorded historic earthquakes or could be a computer generated synthetic data appropriately complementing the simulation objective.
The selection of an appropriate candidate from the pool of earthquake data is governed by many factors. For example, the chosen building plan can be analyzed for its modal frequencies and candidate earthquake data is then selected from the pool which does not adversely affect the simulation objective by exaggerating the building response due to resonance, or making the displacement response unstable for building components. Candidate earthquake data may also be selected on the basis of site location of the building, for example if the building plan is imitating a real life structure, the historic earthquakes occurred in the surrounding geographical location could be used for the purpose of creating the simulation. Earthquake data selection could also be affected by target audience. For example, if target audience is school children and simulation objective is for just a mild sensitization or trauma free experience, a low intensity earthquake might be selected for the simulation. On similar lines target audience could be professionals related to construction industry, search and rescue professionals, engineering/architecture faculty and students, government officials or other specific target groups, with each group influencing the selection in a somewhat different way. The selection is also affected by exact training purpose, which could be for example awareness, response training or search and rescue training. It should be noted that these factors influence the formation of a pool of candidates but ultimately the further analytical steps in the process may reject any candidate based on the estimated unsuitability of the data for the purpose.
A major object of the simulation is to correctly depict things which happen during an earthquake. Computer assisted numerical analysis techniques such as "finite element methods" are well described in literature to perform this type of analysis, but the objective of such analysis is to usually generate response data in vector form or simple graphical forms. The simulation objective is not only to generate this data but also to visualize it in a realistic manner. This requirement creates additional constraint and peculiarities while carrying out the said analysis.
As a preparatory step for this analysis, structural models of chosen building and internal objects are created at step (103). This process can be iterative and incremental. Structural models generally contain nodes and elements. Nodes are key-points of building/object on which force/displacement is applied and their movement is recorded in response of applied force/displacement. Properties at nodes are obtained from the elements which connect two nodes (i.e. beam, column, plate etc.) and depend on dimension (width, height, length) and material (concrete, steel, any other metal) of connecting element. Structural engineering models can be designed to simulate both linear as well as non-linear behaviour to accurately replicate the earthquake time history response as described in Figure-2. Further, the structural engineering models of the buildings and the said elements are created keeping into the consideration, the requirements and lim itations of the visualization
Referring now to figure 2, a process of creating structural engineering models (103) capable of simulating linear and non-linear behaviour is illustrated. Based on simulation objective, it is decided if non-linear behaviour modelling and analysis is required for that particular object at step (201 ). Non-linear modelling depicts behaviour of material well beyond normal day-to-day force which is common in the case of earthquake and such disasters. Such modelling enables accurate prediction of cracking in masonry or concrete, dents in metallic objects and other such behaviour which is not possible to model through linear modelling. While designing linear models, a suitable element mesh configuration is estimated taking into the consideration the requirements and limitations of the visualization objective at step
(202). While designing non-linear behaviour models, a suitable mesh configuration and other parameters of the models are estimated taking into the consideration the requirements and limitations of the visualization objective at step (203). To illustrate this with an example, to simulate the distortions occurring in the plates of an elevator, the element density of the structural mesh is carefully chosen. A very coarse distribution of element mesh might turn out inadequate to simulate the required non-linear response at the same time a very dense distribution of element mesh might make it very difficult or infeasible to map the earthquake response onto the visual model, thus a solution needs to be calibrated which suite both structural and visualization requirements and this requires deep insights of both fields. Apart from structural arrangements, at steps (204) and (205) physical and numerical attributes of these models are selected carefully to meet the required simulation objective. After creation, these models are scrutinized analytically if they meet the visualization objective or not as mentioned in steps (206) and (207), and if they do not meet them, they are changed appropriately until the objective is met and this process is repeated.
Figure-3, Figure -4A and Figure-4B, shows flow charts of the process of performing numerical analysis for the earthquake of step (104) of figure 1. These flow charts illustrates major elements of step (104) for linear, non-linear and crack/damage simulation respectively. On the basis of the structural plan of the object, linear and/or non-linear structural model is created as in steps (301 ) and (401 A). Physical properties of the nodes and elements of these models are carefully chosen as in steps (302) and (402A) and could be tweaked as required by the simulation objective and specific visualization requirements. Once the model is ready the base motion data needs to be specified as in at steps (303) and (403 A). For example, if the object of interest is the building structure, scaled/modified version of the earthquake candidate data will act as base motion data. In another example, if object of interest is a chair on a specific floor of the building, the pre-calculated floor motion response will be fed as base motion data for this particular object. Apart from the base motion data additional loads or dynamic constraints might be specified according to the scenario arrangement. An example of such a constraint will be a photo-frame, hinged to the
wall with the help of a rope. After having the models, base motion data and dynamic constraints/loads in place, this data can be feed into computer software to generate time history response for the said object as in steps (304) and (404A). Process of estimating displacement of various nodes of structure/object due to the earthquake motion is called "time-history" analysis. This analysis gives displacement of various nodes based on earthquake motion data and additional constraints. 'ANSYS Structural Mechanics Solution' is an example of such software which can be used to perform the stated numerical analysis of the time history analysis. The software uses advanced physics equations and their numerical solutions to predict motion of these components during the earthquake. The time history response is estimated by using computer -assisted numerical simulation on the basis of earthquake engineering principles.
Once the numerical analysis result is generated, it is scrutinized again to see if the generated output meets all the simulation objectives as in steps (305) and (405A). If it does so, time history response is recorded for further use. Final time history response can contain motion profiles, stress/strain profiles or any other desired physical quantity which can be helpful in creating the visualization. In case instability creeps into the system or the generated result does not meet simulation objective, causal analysis for the failure is performed. If the cause of the failure is the chosen earthquake data, then it is removed from the pool as in steps (306) and (406A). This whole process can be repetitive in the sense that during the course of iteration some parameters in steps (301), (302), (303), (304), (401 A), (402A), (403A) and (404A) can be tweaked until a satisfactory result is obtained.
Apart from creating motion time history of the structure, it is equally important to simulate crack, damage and/or collapse in the structure for creating realistic visuals and lasting impression in the mind of the viewer.
Further, figure-4B illustrates the process of estimating characteristic parameters to simulate these kinds of non-linear effects. To illustrate with an example, cracks formed during the course of an earthquake are highly non-linear and erratic
phenomenon. To model such behaviour, first a non-linear time history analysis is performed on the structure of interest. On the basis of the result strategic locations are identified on the structure where such cracks might appear with high probability as in step (401 B). Characteristic parameters that may aid in the correct visualization of such behaviour are identified. For example, in the case of cracks, these parameters are maximum depth, maximum width and evolution with time. Physical attributes such as force and moment time history which may affect these characteristic parameters are collected from the location of interest as in step (402B). As in step (403B) physical properties of the element or a group of elements on which crack/damage will appear at the location of interest are collected as well. Once this data is in place, it is fed into complex and heuristic based non-linear empirical equations in order to estimate the required characteristic parameters as shown in step (404B). Frequency analysis of the earthquake data might also be fed into these equations to estimate propagation and evolutions of the said characteristic parameters with time.
Once the earthquake time history responses are ready the next steps are to visualize this simulation data in a way that can maximize the impact of sensitization. The best way to do this is to have the visualization as close to realty as possible. In order to create these realistic visualizations advanced knowledge of computer graphics and cinematography is required. The visualization process, as shown in step (105) of figure- 1 , starts with the creation of 3D computer models. On the basis of structural model of the object its corresponding 3D model is created as shown in Figure-5. While creating these 3D models particular attention is given to surface details, lighting conditions and texturing so as to mimic the real world as close as possible during the experience. Structural models act as a kind of skeletons for the creation of 3D visual models. To illustrate with an example, (501 ) structural model of the building is taken as a skeleton and on the basis of this model a building facade (502) is created as shown. The same principle applies to internal contents or any additional structures which are part of the scenario, for example (503) acts as a skeleton for (504), 3D model of a chandelier. The 3D modelling process can be carried out using numerous 3D software platforms such as Autodesk Maya, Autodesk 3D Studio Max,
Blender to name a few. The process can itself be guided with the help of real life photographs of textures, lighting conditions etc.
The next step in visualization is to map the earthquake time history response estimated earlier to the corresponding 3D model as in (106). The result of this mapping is a dynamic animation showing the things happening in the scenario during the course of the earthquake. Figure-6 shows overview of this mapping process. Earthquake response is not limited to simply the displacement profiles of the object during the course of the simulation but can also include things like crack formation, dust-debris and puff cloud formation etc. The visualization aspects of these responses can be governed directly by the numerical results as in the case of motion profiles as described in step (6.01), but can also be mapped qualitatively as shown in step (603) or a combination of both qualitative and quantitative approach as illustrated in step (602). While doing a qualitative mapping of the earthquake response onto the 3D object, earthquake engineering expertise play a major role in mimicking the real earthquake as closely as possible. To illustrate each of the mapping paradigms (601 ) and (602) with an example, Figure-7 and Figure-8 chalk out the mapping process in detail.
Earthquake motion response of the objects structure depends on many factors and can be highly complex and erratic during the earthquake. To map the motion profile of a particular object onto the corresponding 3D model, first it needs to be classified into appropriate category as shown in step (701). If the object structure does not significantly distort during the earthquake it can be classified as following approximately rigid body motion, for example a hard wooden photo-frame might behave like a rigid body during the course of the simulation. If object is an extended assembly such as a building structure, parts of facade can be classified to follow piecewise rigid motion, i.e. there is some amount of distortion across nodes and elements, but the general structure more or less remains same. If the major portion of an object is going under large distortions the motion is classified as non-rigid, an example of such a distortion will be the plates of an elevator colliding with enclosing slabs producing erratic deformations in the plate body. However it should
be noted that this is done to simplify mapping process, in principle any parametric function can be used for mapping if it fulfils simulation objective. Depending upon the classification of motion profiles step (702) decides appropriate course of action required for the mapping.
For mapping the rigid motion profiles, the displacements of various nodes are taken and a least square solution is calculated which best approximates the required rotation-translation matrix for the displacement as in step (703). These matrices can then be key-framed as in step (706) to create the animation of the 3D object. For mapping the piecewise motion profiles, lattice based animation techniques are used. Strategic lattice points are defined on the object facade, and node displacements are mapped onto these points as in step (704). These lattice point movements then can be key-framed as in step (707) to create the animation of the 3D object. For mapping non-rigid motion onto 3D models, first a smooth subdivision surface representation of the 3D object is created, thereafter lattice points are defined at strategic locations which control the movement of the subdivision surface in a smooth manner. Once lattice points are in place, individual node displacements are mapped parametrically on these lattice points as in step (705). The distribution or density of nodes and elements created for the structural model play an important role in deciding the fidelity of such non-rigid animations. Further, these lattice point movements are key- framed to generate non-rigid deformation animation for the 3D object as in step (708).
Apart from motion profiles of the objects in the earthquake response, secondary effects do occur during the course of such an event. Formation of cracks on the walls or at beam column junction is very common during earthquakes. To map such effects with high fidelity a combination of numerical and qualitative methodology is used. As described in the Figure-8, stress/strain profiles calculated during the numerical analysis can be used to arrive at strategic locations where possible cracks might appear; moreover these parameters can be used to arrive at approximate maximum depth and width of a crack at the point of interest as in step (802). Qual itative approach comes into picture when determining the shape of a crack that
might form at the point of interest, for example by studying the real world photographs of crack patterns during real earthquakes , a library of crack shape patterns in vector form can be created as in step (801). Once such a library is there, an area of interest on the 3D object is chosen where these cracks can appear with high probability. An appropriate shape vector is chosen from the library which governs the shape of the crack that will appear in the animation. Maximum width and depth, estimated earlier at the point of interest governs the extent of the crack that will appear during the course of animation as in step (803). Once location, shape and extent of a crack are decided, the frequency analysis of the earthquake can be used to derive the propagation and evolution of the crack with time as in step (804). All of these can be key-framed to generate a displacement map textured onto the area of interest creating an effective 3D animation for crack formation as in step (805).
Apart from motion and crack profiles there are other effects occurring during the course of an earthquake such as formation of dust and debris, puffs, smoke, light fluctuations etc to name a few. A qualitative approach based on the knowledge of earthquake engineering and cinematography can be used to simulate these effects as in step (603). The earthquake time history response can be used to identify possible strategic points at which such effects are to appear with high probability. Computer graphics methods such as particle systems or fractals can be used to simulate these effects. Light fluctuation occurring during the real earthquakes can be studied and artistically modelled in the simulation to mimic the real life effect. Although these effects are not necessary to be included in the simulation but they serve a purpose of increasing the realism and fidelity of experience. They can also substantially add value to the simulation objective. The visualization could be performed either as a computer-implemented real-time rendering process or using video and audio sequences generated with the help of computer-assisted off-line rendering process.
Visual animations on immersive virtual reality platforms provide a sense of being present there in the simulation; this sense of presence can be further enhanced with the help of correct audio cues. Sounds produced during pre-recorded earthquakes are
used as a source or as guidance for creating simulation sounds. Various sounds occurring during the earthquake may include sounds arising out of collisions or collapse of scenario objects, ambient sounds, human voices/screams etc. For the purpose of realistically incorporating these sounds into the simulation, the location of sound sources and their propagation with time is modelled as in step (107). Computer assisted methods for mixing sounds, as practiced in cinematography are used to produce multichannel spatial sounds which correctly replicate effects like Doppler, echo and decay.
Once the visual and audio animation is ready, the next steps are to present this animation on the virtual reality platform of interest as shown in Figure-9. Depending on the configuration of intended platform, required rendering output may differ. For example a 4 walled stereoscopic CAVE system requires 8 separate visual frames (left eye x 4, right eye x4) for each individual animation time step and can require as many audio channels as supported by the platform. On the other hand a simple one screen projection platform may require only 2 separate (one for left and one for right eye) visual frames per animation time step. Not only the number of frames but also the camera parameters for rendering an individual frame may differ across platforms, for example a cubical CAVE might require different camera parameters for rendering then a curved screen cylindrical system. On the similar lines placement of audio equipments can affect the rendering parameters for audio tracks. As described in step (901 ), depending on the virtual reality platform of interest rendering camera parameters are defined.
Path of an observer (camera assembly) in the earthquake scenario is decided based on simulation objective and cinematographic aspects as in (902). For example, for the purpose of rescue training mission the camera path aligns with the training path which will be taken during the rescue mission. If the simulation objective is sensitization of school children, a less catastrophic camera path might be chosen to complement the simulation objective. Similarly if real-time rendering is being performed when simulation is playing on the platform, path of the camera can even be decided freely and interactively by the observer during the course of the
simulation. The observer/camera motion is affected by the earthquake itself, which is accounted by adjusting the camera assembly displacement with the numerical time history response at the point of interest on the path as in step (903). To illustrate this with an example, an observer at first floor of a building will feel different earthquake motion then an observer at 7th floor of the same building due to different locations having their own peculiar time history responses.
Frames can finally be rendered with the camera assembly as shown in step (904). Rendering process itself can be performed in real time with the help of computers or it can be done as an offline batch process to generate video and audio sequences later playable on the virtual reality platform of interest. Offline visual rendering is performed in photo-realistic manner with the help of computer software such as Mental Ray, POV Ray etc to produce image sequences of exceptional quality and high realism. Advanced computer graphics rendering techniques such as ray-tracing and global illumination are used by the software to arrive at the resulting photographic images. On the similar lines high quality audio rendering can be performed in real-time or offline. These rendered sequences can be played back on the virtual reality platform in sync, to impart a wonderful immersive earthquake experience fulfilling the entire simulation objective for the participant.
At step (109), the process (1000) ends.
In another embodiment, the process is either non-interactive or interactive with the simulation platform. When we have non-interactive process, the response of building/inner objects cannot be altered with respect to the response of persons inside the simulation. Further, when we have interactive process, the response of building/inner objects can also be altered with respect to the response of persons inside the simulation.
In another embodiment, the process can be used to simulate any disaster which is similar to an earthquake and requires structural analysis and time history generation. For example a simulation scenario where a building is facing destruction by a
tornado or a hurricane can be simulated with the embodiment process. Minor modifications in the process, for example replacing earthquake data with the tornado disturbance data, may be induced in the process to simulate the scenario.
It is to be understood that the present invention is not limited in its application to the details of the construction and to the arrangement of the components as mentioned in the above description or illustrated in the drawings. However, it is to be taken as the preferred example of the invention and that various changes in the shape, size and arrangement of parts considering the space constraint may be resorted to without departing from the spirit Of the invention. The invention is capable of other embodiments and of being practised and carried out in various ways. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.
Claims
1 . A computer-assisted process for creating earthquake disaster simulation on virtual reality platform, the process comprising steps of:
Planning a simulation scenario with pre-defined building structures having pre-defined elements therein;
selecting a pre-defined earthquake ground motion data for the earthquake disaster simulation and simultaneously creating structural engineering models of the said buildings and the elements therein;
estimating time history response of the said buildings and the said elements for the selected earthquake by using computer-assisted "time history analysis"; creating three dimensional (3D) computer models of the said buildings and the said elements therein;
mapping the said time history responses onto the said 3D models to create 3D animations and simultaneously creating audio sequences of sounds occurring during the earthquake thereof;
visualizing the said 3D animations and generating multichannel audio tracks, thereby creating a simulation of the earthquake on the virtual reality platform of interest.
2. The process as claimed in claim 1, wherein earthquake ground motion data is pre-recorded historic earthquake data.
3. The process as claimed in claim 1 , wherein earthquake ground motion data is a computer generated synthetic ground motion data.
4. The process as claimed in claim 1, wherein the earthquake ground motion data is selected by using structural analysis of the said scenario objects, requirements of the intended audience, site and location of the said buildings and/or any other specific simulation objective.
5. The process as claimed in claim 1, where in time history response is estimated by using computer-assisted numerical simulation on the basis of earthquake engineering principles.
6. The process as claimed in claim 5, where in time history response is generated to simulate both linear as well as non-linear behavior.
7. The process as claimed in claim 5, where in time history response is extended with the numerical analysis and heuristics to estimate characteristic parameters for the secondary effects like cracks, damage and collapse.
8. The process as claimed in claim 1 , where in time history response is mapped onto corresponding 3D models quantitatively, qualitatively or a combination of the two thereof.
9. The process as claimed in claim 9, where in mapping includes mapping of motion profiles, mapping of cracks/damage/collapse and/or mapping of effects like dust-debris, puffs and smoke.
10. The process as claimed in claim 1 , where in visualizing the said 3D animations could be accompanied with the creation of appropriate earthquake sounds complementing the visual events on the basis of earthquake engineering principles.
1 1 . The process as claimed in claim 1 , wherein the visualization is performed either as a computer-implemented real-time rendering process or using video and audio sequences generated with the help of computer-assisted off-line rendering process.
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| US9418477B2 (en) | 2014-09-30 | 2016-08-16 | Cae Inc. | Rendering damaged-enhanced images in a computer simulation |
| US9430875B1 (en) | 2014-09-30 | 2016-08-30 | Cae Inc. | Updating damaged-enhanced 3D polygon meshes |
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| WO2020054947A1 (en) * | 2018-09-12 | 2020-03-19 | Korea Institute Of Geoscience And Mineral Resources | Seismic vulnerability analysis system of user's living space and seismic vulnerability analysis method of user's living space using the same |
| US11645799B2 (en) | 2018-09-12 | 2023-05-09 | Korea Institute Of Geoscience And Mineral Resources | Seismic vulnerability analysis system of user's living space and seismic vulnerability analysis method of user's living space using the same |
| CN110580443A (en) * | 2019-06-19 | 2019-12-17 | 深圳大学 | Low-altitude near-real-time building earthquake damage assessment method |
| CN112270092A (en) * | 2020-10-28 | 2021-01-26 | 重庆大学 | Multi-iteration-point artificial wave response spectrum fitting method for self-recognition of hard points |
| CN112270092B (en) * | 2020-10-28 | 2021-08-10 | 重庆大学 | Multi-iteration-point artificial wave response spectrum fitting method for self-recognition of hard points |
| CN113990169A (en) * | 2021-10-26 | 2022-01-28 | 新兴际华科技发展有限公司 | Distributed virtual simulation earthquake emergency drilling system |
| CN115983139A (en) * | 2023-03-01 | 2023-04-18 | 北京科技大学 | Building group earthquake falling object scene mixed reality display method and device |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2011132205A8 (en) | 2012-01-05 |
| WO2011132205A3 (en) | 2012-03-01 |
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