CN108492371A - A kind of three-dimensional building model dynamic and visual method towards fire - Google Patents

Abstract

The invention discloses a dynamic visualization method of a fire-oriented three-dimensional building model. In order to simulate the texture change of the three-dimensional building model, a method of generating a two-dimensional noise texture map based on fractal noise and mixing it with the original texture of the three-dimensional building model is used; the completion method is based on PhotoShop Automatically generate line textures and attach them to 3D architectural models to simulate cracks; and can simulate shattering of 3D architectural models. The present invention can more comprehensively represent various changes that may occur in the building structure during a fire, and makes up for the shortcomings of the existing method that the effect is single and the real-time performance is difficult to satisfy, so as to provide an experience that improves the sense of reality for the fields of virtual reality and visual simulation. At the same time, people can feel the fire hazard more intuitively and improve their awareness of fire prevention.

Description

A fire-oriented dynamic visualization method for 3D building models

technical field

The invention belongs to the field of computer graphics, in particular to a dynamic visualization method for a fire-oriented three-dimensional building model.

Background technique

Virtual reality has ushered in another rapid development in recent years. Its characteristics of integrating computer, multimedia, human-computer interaction, computer graphics and other related disciplines have greatly shortened the distance between virtual reality and reality. In the three-dimensional virtual world created by computers, people can not only see and hear, but also can freely interact with their own world with their hands. Of course, people are interested in using computers to build a more realistic and interactive virtual world Higher requirements have also been put forward, and the simple reproduction of realistic scenes in the past has become more and more difficult to meet the needs. The process of simulating many seemingly simple physical behaviors in the real world is very difficult, which has become a bottleneck restricting the realistic experience. Among them, the simulation of fire scenes has always been a research direction that researchers and engineers pay close attention to. How to truly reproduce the changes of building structures in fire is the key to improving people's realistic experience in the virtual environment. People have a more intuitive and clear understanding of the hazards of fire.

Among the existing fire scene simulation methods, the finite element method is the main method, and experiments are carried out by setting relevant parameters in the finite element software to simulate the development of the fire and the damage caused by the fire. However, the results of such methods are presented in two-dimensional form, which is often not intuitive enough. Moreover, such methods involve a large number of numerical calculations, which are inefficient, and are not suitable for fields such as virtual reality that have high requirements for real-time performance.

Among them, the simulation of object damage has a long history. The simulation methods are mainly divided into two categories, one is based on physics, and the other is based on geometry. The physics-based method needs to use the knowledge of material mechanics, fracture mechanics and other disciplines as the background, and combine the characteristics of the material itself to analyze and simulate its behavior when it is under force. Due to the need to strictly follow the laws of physics, that is, the damage of the object caused by the external force will eventually lead to the failure of the object. Structural damage occurs between internal parts, and then externalized to the surface, resulting in cracks or directly causing the object to break, resulting in fragments. The simulation of this process often requires the establishment of complex mathematical models, combined with computer graphics methods, to render and display. However, this process includes a large number of complex force analysis, and when solving the established mathematical model, it has to solve complex calculus equations, which puts forward high requirements on the real-time performance of the simulation. Today, when computing power has been greatly improved, this method is still difficult to use in real-time scenarios, but more in military simulation, engineering fields, etc.; although existing geometry-based methods can meet real-time requirements, However, there is still the problem of single simulation effect, which can neither comprehensively consider the external performance of the object in different stages of destruction, nor can it simulate the effects of object destruction in a variety of ways.

Contents of the invention

In order to solve the deficiencies in the prior art, the present invention provides a fire-oriented dynamic visualization method of a three-dimensional building model, in order to comprehensively express the various changes that may occur in the building structure during a fire, and to make up for the effects of the existing methods Single, real-time is difficult to meet the defects, so as to provide a method and technical means to improve the realistic experience for the fields of virtual reality, visual simulation, etc., and at the same time make people feel the fire hazard more intuitively, and improve the awareness of fire prevention.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A kind of fire-oriented three-dimensional architectural model dynamic visualization method of the present invention is characterized in following steps:

Step 1. Use the fractal noise algorithm to generate a two-dimensional noise texture map T ₁ , and use formula (1) to perform texture mixing on the two-dimensional noise texture map T ₁ and the surface texture map T ₂ of the three-dimensional building model to obtain the changed Surface texture map T of the 3D building model:

T＝T ₁ ×x+(1-x)×T ₂ (1)

In formula (1), x is the mixing coefficient;

Step 2. Complete the crack simulation of the 3D building model based on PhotoShop:

Step 2.1. Create a new blank rectangular canvas with a size of W×H in the script language, and take any vertex of the blank rectangular canvas as the origin O, and the two sides adjacent to the origin O as the X axis and Y axis, so as to establish the coordinate system XOY;

Step 2.2. In the coordinate system XOY, set any starting coordinate point start(x ₁ , y ₁ ) and end point coordinate point end(x ₂ , y ₂ );

Step 2.3. Randomly generate n two-dimensional coordinates on both sides of the straight line determined by the starting point coordinate point start(x ₁ , y ₁ ) and the end point coordinate point end(x ₂ , y ₂ ), and calculate the The n two-dimensional coordinates are sorted in ascending order according to their X coordinates, and the sorted n two-dimensional coordinates are obtained and stored in the array LineArray[n];

Step 2.4: Initialize each two-dimensional coordinate in the array LineArray[n] as a PathPointInfo class type;

Step 2.5: initialize the array LineArray[n] to the SubPathInfo class type, and pass it in as a parameter of the function pathItems.add(), so that the adjacent two-dimensional coordinate points in the array LineArray[n] can be expressed as A line segment connected end to end, and then get the start coordinate point start(x ₁ ,y ₁ ) as the starting point, the end point coordinate point end(x ₂ ,y ₂ ) as the end point, and the sorted n two-dimensional coordinates as The polyline segment of the middle node;

Step 2.6: Call the function strokePath() to draw the polyline segment and use the function charIDToTypeID(id) to call the NormalMapFilter plug-in to obtain the normal texture corresponding to the polyline segment, where id is the plug-in index number;

Step 2.7, attaching the normal texture corresponding to the polyline segment to the 3D architectural model, thereby simulating cracks in the 3D architectural model;

Step 3. Fragmentation simulation of the 3D building model:

Step 3.1, mapping the three-dimensional architectural model onto a two-dimensional plane to obtain a rectangular area L; taking any vertex of the rectangular area as the origin o, and the two sides adjacent to the origin o as the x-axis respectively and the y axis, thus establishing the coordinate system xoy;

Step 3.2, utilize the function f shown in formula (2) or the function f shown in formula (3) or the function f shown in formula (4) to generate m seed point coordinates:

f=R(b,t,m) (2)

In formula (2), R( ) is a random number function, b and t are any two coordinate points in the coordinate system xoy, and a rectangular frame is determined by the coordinate points b and t, and the rectangular frame is is the generation range of m seed point coordinates;

In formula (3), L represents the rectangular area, s is the interval value of any two adjacent seed point coordinates in the m seed point coordinates, λ is a disturbance term, and the value range is (0, s );

f=d(p _i ,G)-r (4)

In formula (4), G is the coordinate of any point in the rectangular area L, p _i is the coordinate of the i-th seed point, d(p _i , G) is the Euclidean distance function between two points, r is a constant, i= 1,2,3...m;

Step 3.3, using the generated m seed point coordinates as input parameters of the scan line algorithm, using the scan line algorithm to divide the rectangular area into m parts and recording the boundary information of each part;

Step 3.4, performing triangular meshing processing on the 3D architectural model according to the boundary information of each part, to generate m fragments;

Step 3.5, using formula (5) to obtain the external force F _i of the i-th fragment:

In formula (5), F is the self-defined initial external force value, and D(p _i , G) is the square function of the Euclidean distance between two points;

Step 3.6, apply the external force F _i of the i-th fragment to the i-th fragment, so that the i-th fragment moves under the external force F _i of the i-th fragment, thereby simulating the first The breaking motion of i pieces;

The dynamic visualization process of the three-dimensional building model is composed of the changed surface texture map T of the three-dimensional building model, the normal texture corresponding to the polyline segment, and the broken simulation of the three-dimensional building model.

The fire-oriented three-dimensional architectural model dynamic visualization method of the present invention is also characterized in that the step 3.5 and step 3.6 can also carry out the crushing motion simulation in the following manner:

Dividing the three-dimensional architectural model into an upper part model and a lower part model, according to the positions of all the fragments in the three-dimensional architectural model, randomly adding the same external force to the fragments belonging to the lower part model, so that the fragments belonging to the lower part model The fragments of the model are displaced, and the fragments belonging to the upper part of the model are naturally dropped under the action of gravity, thereby forming the collapse phenomenon of the three-dimensional architectural model.

Compared with prior art, the beneficial effect of the present invention is:

1. The present invention adopts the method of texture mixing when simulating the surface texture change of a three-dimensional building model, and sets a mixing coefficient in the texture mixing at the same time. By adjusting the coefficient, different degrees of surface texture changes of the three-dimensional building model can be simulated;

2. When simulating the cracks of the three-dimensional building model, the present invention adopts the method of adding normal texture to the model, and at the same time proposes an automatic generation method of normal texture based on PhotoShop, which can quickly generate the normal texture that meets the user's expected effect. Line texture, compared with the existing normal texture production method, this method is more efficient, fully automatic, and can be completed without too much user intervention;

3. When the present invention simulates the breaking of a three-dimensional building model, it is divided into two parts: model division and movement after breaking, so that the overall breaking simulation effect is more realistic;

4. The present invention proposes three different subdivision methods when dissecting the model, and it is completed based on the geometric method without a lot of complex physical calculations, so that the method not only meets the real-time requirements, but also increases the model fragmentation effect diversity;

5. The present invention proposes two different motion simulation methods when simulating the movement of the broken model, which also does not require complex physical calculations, which ensures the overall efficiency of the method and increases the diversity of crushing simulation effects.

Description of drawings

Fig. 1 is a schematic flow sheet of the method of the present invention;

Fig. 2 is the simulation diagram of surface texture change of three-dimensional architectural model in the present invention;

Fig. 3 is the three-dimensional building model crack simulation figure among the present invention;

Fig. 4 is a broken simulation diagram of a three-dimensional building model in the present invention.

Detailed ways

In order to better understand the technical solutions of the present invention, further description will be given below with reference to the drawings and specific embodiments.

The building structure often presents various changes in the fire. According to the method, the invention simulates the changes of the three-dimensional building model under the fire situation. , the 2D noise texture is first generated by the fractal algorithm, and then mixed with the original texture of the 3D building model; when simulating the cracks of the 3D building model, the normal texture is automatically generated through the script language based on PhotoShop, and the automatically generated The normal texture of the 3D building model is attached to the 3D building model to simulate the cracks on the surface of the 3D building model; when the 3D building model is broken and simulated, it is first necessary to map the 3D building model to a 2D plane, and use a certain method within the range of the 2D plane After generating the seed points, the scanning line algorithm is used to divide the two-dimensional plane, and then the boundary information of each part after division is recorded, and the three-dimensional building model is triangulated according to the boundary information to generate fragments; finally, in order to simulate the fragments Motion, exerting an external force in some way on the fragments.

Specifically, the process of a fire-oriented 3D building model dynamic visualization method is as follows:

Step 1. Use the fractal noise algorithm to generate a two-dimensional noise texture map T ₁ , and use formula (1) to perform texture mixing on the two-dimensional noise texture map T ₁ and the surface texture map T ₂ of the three-dimensional building model to obtain the changed three-dimensional building The surface texture map T of the model:

T＝T ₁ ×x+(1-x)×T ₂ (1)

In the formula (1), x is a mixing coefficient, and in this embodiment, the value of x is 0.3. The result after texture blending is shown in Figure 2.

Step 2. Complete the crack simulation of the 3D building model based on PhotoShop:

Step 2.1. Create a new blank rectangular canvas with a size of W×H in the script language, and take any vertex of the blank rectangular canvas as the origin O, and the two sides adjacent to the origin O as the X axis and the Y axis respectively, so that Establish a coordinate system XOY; in this embodiment, the size of the blank rectangular canvas is 400×300, and the vertex at the lower left corner of the rectangular canvas is taken as the origin O, the side adjacent to the vertex in the horizontal direction is used as the X axis, and the vertical direction is parallel to the vertex. The adjacent side serves as the Y axis to establish the coordinate system.

Step 2.2. In the coordinate system XOY, set any starting coordinate point start(x ₁ ,y ₁ ) and end point coordinate point end(x ₂ ,y ₂ ). In order to obtain a more expected normal texture, generally set the starting point The two coordinate points of the start point and the end point are located near the diagonal of the rectangular canvas; in this embodiment, the coordinates of start(x ₁ , y ₁ ) are selected as (320,10), and the coordinates of end(x ₂ , y ₂ ) are selected as ( 15,270).

Step 2.3. Randomly generate n two-dimensional coordinates on both sides of the straight line determined by the starting coordinate point start(x ₁ ,y ₁ ) and the end point coordinate point end(x ₂ ,y ₂ ), in order to improve the algorithm execution efficiency As efficient as possible, the value of n should not be set too large. In this embodiment, n is set to 50, and the n two-dimensional coordinates are sorted in ascending order by using the quick sort algorithm according to their X coordinates, and n two-dimensional coordinates after sorting are obtained. dimensional coordinates and stored in the array LineArray[n];

Step 2.4: Initialize each two-dimensional coordinate in the array LineArray[n] as the PathPointInfo class type;

Step 2.5: Initialize the array LineArray[n] as the SubPathInfo class type, and pass it in as a parameter of the function pathItems.add(), so that the adjacent two-dimensional coordinate points in the array LineArray[n] can be expressed as a segment connected end to end line segment, and then get the starting point start(x ₁ ,y ₁ ) as the starting point, the end point coordinate point end(x ₂ ,y ₂ ) as the end point, and the sorted n two-dimensional coordinates as the intermediate node fold line segment;

Step 2.6: Call the function strokePath() to draw the polyline segment and use the function charIDToTypeID(id) to call the NormalMapFilter plug-in to obtain the normal texture corresponding to the polyline segment, where id is the index number of the plug-in, and the id number will vary depending on the software environment There are differences, and you need to set it according to your actual situation;

Step 2.7, attaching the normal texture corresponding to the polyline segment to the 3D architectural model, thereby simulating the cracks of the 3D architectural model. After attaching the obtained normal texture to the 3D building model, the result shown in Figure 3 is obtained.

Step 3. Fragmentation simulation of the 3D building model:

Step 3.1. Map the three-dimensional architectural model onto a two-dimensional plane to obtain a rectangular area L'; take any vertex of the rectangular area as the origin o, and the two sides adjacent to the origin o as the x-axis and the y-axis respectively, so that Establish a coordinate system xoy; in this embodiment, the size of the rectangular area L obtained after mapping the three-dimensional building model to a two-dimensional plane is 800×600, and the upper left corner vertex of the rectangular area is used as the origin o, and the vertex is aligned with the horizontal direction The adjacent side is used as the x-axis, and the vertical direction and the adjacent side of the vertex are used as the y-axis to establish a coordinate system.

Step 3.2, utilize the function f shown in formula (2) or the function f shown in formula (3) or the function f shown in formula (4) to generate m seed point coordinates:

f=R(b,t,m) (2)

In formula (2), R(·) is a random number function, b and t are any two coordinate points in the coordinate system xoy, and a rectangular frame is determined by the coordinate points b and t, and the rectangular frame is the coordinates of m seed points The range of generation;

In formula (3), L represents a rectangular area, s is the interval value of any two adjacent seed point coordinates among the m seed point coordinates, λ is a disturbance item, and a larger value of λ will make the generated seed point Too sparse. On the contrary, when the value of λ is small, the seed points will be too dense, which will affect the execution efficiency of the subsequent algorithm. Therefore, in order to simulate a better fragmentation effect, the value range of λ is generally set to (0,s);

f=d(p _i ,G)-r (4)

In formula (4), G is the coordinate of any point in the rectangular area L, p _i is the coordinate of the i-th seed point, d(p _i , G) is the Euclidean distance function between two points, r is a constant, i=1, 2,3...m; let f=d(p _i ,G)-r=0, even if the generated seed point is located on the circle with G as the center and r as the radius, it can simulate some special types of three-dimensional The shattering effect of architectural model components.

In this embodiment, the function f shown in formula (2) is used as the seed point generating method, m=70, b and t are (0,0), (500,700) respectively.

Step 3.3, using the generated m seed point coordinates as input parameters of the scan line algorithm, using the scan line algorithm to divide the rectangular area into m parts and recording the boundary information of each part;

Step 3.4, according to the boundary information of each part, perform triangular meshing processing on the 3D building model (when triangular meshing, pay attention to the coordinate system specification in the software environment used, so as not to get wrong meshing results) to generate m fragments; this method of dividing the model to generate fragments can guarantee fast and efficient operation because it is based on the geometric method.

Step 3.5, using formula (5) to obtain the external force F _i of the i-th fragment:

In formula (5), F is the self-defined initial external force value, and D(p _i , G) is the square function of the Euclidean distance between two points;

Step 3.6, apply the external force F _i of the i-th fragment to the i-th fragment, so that the i-th fragment moves under the external force F _i of the i-th fragment, thereby simulating the i-th fragment in the three-dimensional building model Breaking movement of fragments; in this embodiment, F is 100, and G is (400,300). The crushing simulation results are shown in Fig. 4.

The dynamic visualization process of the 3D building model is composed of the changed surface texture map T of the 3D building model, the normal texture corresponding to the polyline segment and the broken simulation of the 3D building model.

In addition, steps 3.5 and 3.6 can also simulate the crushing motion as follows:

The three-dimensional architectural model is divided into an upper part model and a lower part model, and according to the positions of all fragments in the three-dimensional architectural model, an identical external force is randomly added to the fragments belonging to the lower part of the model, so that the fragments belonging to the lower part of the model The blocks are displaced, and the fragments belonging to the upper part of the model fall naturally under the action of gravity, thereby forming the collapse phenomenon of the three-dimensional architectural model.

To sum up, in this fire-oriented dynamic visualization method for 3D building models, different methods are used to simulate various changes that may occur in building structures during fires. Among them, in order to simulate the possible texture changes on the surface of the building model, the method of generating noise texture based on fractal noise and mixing it with the original texture of the 3D building model is used; Compared with using physical methods to simulate cracks, this method is simple, efficient and can obtain better simulation results; when simulating the shattering effect of 3D building models, it is improved on the basis of geometric methods, which greatly increases the number of shattering simulations. diversity. Through the simulation of the above three processes, various changes of the building structure in the fire can be simulated more comprehensively, and the simulation results are presented in a three-dimensional perspective, which is more intuitive and vivid. In addition, since the present invention mainly uses geometric methods in the whole process of simulation and does not involve complex physical analysis process, the amount of calculation is greatly reduced, which can completely meet the real-time requirement.

Claims (2)

1. A fire-oriented three-dimensional building model dynamic visualization method is characterized in that it is carried out as follows: Step 1. Use the fractal noise algorithm to generate a two-dimensional noise texture map T ₁ , and use formula (1) to perform texture mixing on the two-dimensional noise texture map T ₁ and the surface texture map T ₂ of the three-dimensional building model to obtain the changed Surface texture map T of the 3D building model: T＝T ₁ ×x+(1-x)×T ₂ (1) In formula (1), x is the mixing coefficient; Step 2. Complete the crack simulation of the 3D building model based on PhotoShop: Step 2.1. Create a new blank rectangular canvas with a size of W×H in the script language, and take any vertex of the blank rectangular canvas as the origin O, and the two sides adjacent to the origin O as the X axis and Y axis, so as to establish the coordinate system XOY; Step 2.2. In the coordinate system XOY, set any starting coordinate point start(x ₁ , y ₁ ) and end point coordinate point end(x ₂ , y ₂ ); Step 2.3. Randomly generate n two-dimensional coordinates on both sides of the straight line determined by the starting point coordinate point start(x ₁ , y ₁ ) and the end point coordinate point end(x ₂ , y ₂ ), and calculate the The n two-dimensional coordinates are sorted in ascending order according to their X coordinates, and the sorted n two-dimensional coordinates are obtained and stored in the array LineArray[n]; Step 2.4: Initialize each two-dimensional coordinate in the array LineArray[n] as a PathPointInfo class type; Step 2.5: initialize the array LineArray[n] to the SubPathInfo class type, and pass it in as a parameter of the function pathItems.add(), so that the adjacent two-dimensional coordinate points in the array LineArray[n] can be expressed as A line segment connected end to end, and then get the start coordinate point start(x ₁ ,y ₁ ) as the starting point, the end point coordinate point end(x ₂ ,y ₂ ) as the end point, and the sorted n two-dimensional coordinates as The polyline segment of the middle node; Step 2.6: Call the function strokePath() to draw the polyline segment and use the function charIDToTypeID(id) to call the NormalMapFilter plug-in to obtain the normal texture corresponding to the polyline segment, where id is the plug-in index number; Step 2.7, attaching the normal texture corresponding to the polyline segment to the 3D architectural model, thereby simulating cracks in the 3D architectural model; Step 3. Fragmentation simulation of the 3D building model: Step 3.1, mapping the three-dimensional architectural model onto a two-dimensional plane to obtain a rectangular area L; taking any vertex of the rectangular area as the origin o, and the two sides adjacent to the origin o as the x-axis respectively and the y axis, thus establishing the coordinate system xoy; Step 3.2, utilize the function f shown in formula (2) or the function f shown in formula (3) or the function f shown in formula (4) to generate m seed point coordinates: f=R(b,t,m) (2) In formula (2), R( ) is a random number function, b and t are any two coordinate points in the coordinate system xoy, and a rectangular frame is determined by the coordinate points b and t, and the rectangular frame is is the generation range of m seed point coordinates; In formula (3), L represents the rectangular area, s is the interval value of any two adjacent seed point coordinates in the m seed point coordinates, λ is a disturbance term, and the value range is (0, s ); f=d(p _i ,G)-r (4) In formula (4), G is the coordinate of any point in the rectangular area L, p _i is the coordinate of the i-th seed point, d(p _i , G) is the Euclidean distance function between two points, r is a constant, i= 1,2,3...m; Step 3.3, using the generated m seed point coordinates as input parameters of the scan line algorithm, using the scan line algorithm to divide the rectangular area into m parts and recording the boundary information of each part; Step 3.4, performing triangular meshing processing on the 3D architectural model according to the boundary information of each part, to generate m fragments; Step 3.5, using formula (5) to obtain the external force F _i of the i-th fragment: In formula (5), F is the self-defined initial external force value, and D(p _i , G) is the square function of the Euclidean distance between two points; Step 3.6, apply the external force F _i of the i-th fragment to the i-th fragment, so that the i-th fragment moves under the external force F _i of the i-th fragment, thereby simulating the first The breaking motion of i pieces; The dynamic visualization process of the three-dimensional building model is composed of the changed surface texture map T of the three-dimensional building model, the normal texture corresponding to the polyline segment, and the broken simulation of the three-dimensional building model. 2. fire-oriented three-dimensional building model dynamic visualization method according to claim 1, is characterized in that, described step 3.5 and step 3.6 can also carry out crushing motion simulation as follows: Dividing the three-dimensional architectural model into an upper part model and a lower part model, according to the positions of all the fragments in the three-dimensional architectural model, randomly adding the same external force to the fragments belonging to the lower part model, so that the fragments belonging to the lower part model The fragments of the model are displaced, and the fragments belonging to the upper part of the model are naturally dropped under the action of gravity, thereby forming the collapse phenomenon of the three-dimensional architectural model.