CN111627092B - Method for constructing high-strength bending constraint from topological relation - Google Patents
Method for constructing high-strength bending constraint from topological relation Download PDFInfo
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- CN111627092B CN111627092B CN202010378419.6A CN202010378419A CN111627092B CN 111627092 B CN111627092 B CN 111627092B CN 202010378419 A CN202010378419 A CN 202010378419A CN 111627092 B CN111627092 B CN 111627092B
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Abstract
The invention provides a method for constructing high-strength bending constraint from topological relation, which comprises the following steps: dividing connected domains of a three-dimensional model to be subjected to dynamic simulation, finding a plurality of different connected domains, and acquiring a geometric body set corresponding to each connected domain; sending out from a point in the geometry set of each connected domain, and acquiring all vertexes of the vertexes in the corresponding k-rings according to the connection relation between the edges and the surfaces; selecting required vertexes from all vertexes of the k ring, determining a connection relation constraint condition of each vertex and the selected vertex in the k ring, and adding the connection relation constraint condition to the three-dimensional model; setting dynamic attributes of the constraint conditions of the connection relation; superposing the connection relation to the constraint conditions of other target objects, and substituting the connection relation into the PBD for resolving; and overlapping the added constraint conditions with the constraint conditions of the three-dimensional model, and submitting the overlapped constraint conditions to a dynamics simulation engine to enhance the bending constraint effect of the three-dimensional model.
Description
Technical Field
The invention relates to the technical field of animation production, in particular to a method for constructing high-strength bending constraint from a topological relation.
Background
In the movie and television industry, simulation (kinetic resolution) of CG animation is an important part. The dynamic simulation method can carry out dynamic simulation on a manufactured three-dimensional solid model (a three-dimensional graph which is described and displayed in a computer by a point side surface and is called a model below) and endows the model with the effects of gravity, a wind field, collision and the like which are close to the real world, so that various deformation effects can be manufactured in a CG animation scene by setting parameters after the model is manufactured, and the effects are interacted with the manual animation effect manufactured by an animator to simulate various special effects which are close to the real world, thereby not only enhancing the details of the animation effect, but also saving the animation manufacturing time;
before dynamics is resolved, the model needs to be set, so that the effect correctness in resolving (simulating) can be guaranteed, for example, a basketball model is thrown into the air, falls onto the ground and bounces, and the basketball model needs to be set to be compressed more greatly after impacting the ground under the gravity effect, and then can be bounced to a high degree. The process of controlling the effects is called adding constraints, the constraints describe the limit effect which can be achieved by the model in the dynamic calculation process, and when the dynamic calculation is carried out, the software ensures that the effect of the model is within a reasonable range according to the constraints and calculates the dynamic effect of the model;
therefore, the constraint setting itself belongs to a very important step of the dynamics calculation, and how to construct the constraint and add the constraint is a direct condition for influencing the dynamics calculation result;
at present, physical simulation is carried out, and a physical simulation algorithm based on the PBD is basically preferred because the physical simulation algorithm has great advantages in resolving speed. However, compared with the traditional RBD or FEM physical simulation algorithm, the PBD has great disadvantages in the aspect of constraint construction. The PBD is based on the iterative solution of the point position, that is to say, the constraint of the PBD is also performed on the model vertex, and only the position constraint relation between the point and the point is supported, while in the traditional physical simulation algorithm, not only the point but also the edge and the surface constraint can be set, and the constraint conditions such as angle, area, volume and the like can be set between the constraints.
Therefore, for the PBD algorithm, more position constraints are needed to be used for simulating other kinds of constraint modes, and more common PBD constraint modes include distance along edges, triangle, cross bands and struts; generally, the several constraint methods are used alone or in a mixed manner enough to satisfy most of the solution requirements, but the several constraint methods are not enough to deal with many high-intensity constraint or high-precision constraint occasions. For example, when a thin metal or a thin plastic needs to be simulated, the general PBD constraint mode basically cannot achieve the corresponding effect well. Because objects such as sheet metal require the use of bending constraints to achieve a degree of flexibility in operation, the general PBD constraint is only that the booth simulates bending constraints, but the booth constraint can only do a gentle cloth effect.
Disclosure of Invention
The invention aims to provide a method for constructing high-strength bending constraint from a topological relation, which solves the problem that a classical PBD constraint mode cannot rapidly process bending constraint with high hardness, does not need to additionally introduce a calculation process to modify a deformation result, and obtains a deformation effect by calculation in the same PBD simulation process by only increasing quantitative constraint conditions so as to enhance the constraint effect.
The invention provides the following technical scheme:
a method of constructing a high-strength bending constraint from topological relations, comprising the steps of:
s1, dividing connected domains of a three-dimensional model to be subjected to dynamic simulation, finding a plurality of different connected domains, and acquiring a geometric body set corresponding to each connected domain;
s2, in the geometry set of each connected domain, sending out from a point, and acquiring all vertexes of the vertexes in the corresponding k rings according to the connection relation between the edges and the faces;
s3, selecting required vertexes from all vertexes of the k ring according to the requirement of calculation accuracy, determining a connection relation constraint condition between each vertex and the selected vertex in the k ring, and adding the connection relation constraint condition to the three-dimensional model;
s4, setting the dynamic property of the connection relation constraint condition;
and S5, overlapping the added constraint conditions with the constraint conditions of the three-dimensional model, and submitting the overlapped constraint conditions to a dynamics simulation engine to improve the bending constraint effect of the three-dimensional model.
Preferably, the geometry set of S1 includes a point set, an edge set, and a face set.
Preferably, the vertices selected at S3 include all vertices within a k-ring boundary or a k-ring.
Preferably, the dynamic properties of S4 include static length, elastic properties, and damping properties.
Preferably, the setting of the dynamic attribute of S4 depends on the result of the physical simulation effect.
The invention has the beneficial effects that: according to the method, during dynamic simulation of animation, a high-strength bending constraint model is directly constructed from the top point of the k ring of the top point on the connected domain, so that the conversion into the traditional algorithm calculation or the addition of a correction program is avoided, the stability and controllability of effect calculation are ensured, all possible constraints of constraint strength can be provided within the range of the three-dimensional model, and the constraint effect is enhanced; meanwhile, the constraint strength can be directly modified by controlling the value of k, and more settings for parameters such as bend angle and the like are not needed.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic diagram of the present invention.
Detailed Description
As shown in fig. 1, a method of constructing a high strength bending constraint from topological relations, comprising the steps of:
s1, dividing the connected domains of the three-dimensional model to be subjected to the dynamic simulation, finding a plurality of different connected domains, and acquiring a geometric body set (a point set, an edge set and a surface set) corresponding to each connected domain;
s2, in the geometry set of each connected domain, sending out from a point, and acquiring all vertexes of the vertexes in the corresponding k-rings according to the connection relation between the edges and the faces;
s3, selecting required vertexes (k-ring boundary or all vertexes in the k-ring) from all vertexes of the k-ring according to the requirement of calculation precision, determining constraint conditions of each vertex and the selected vertexes in the k-ring, and adding the constraint conditions to the three-dimensional model;
s4, setting the dynamic properties (static length, elastic property and attenuation property) of the constraint conditions;
and S5, overlapping the added constraint conditions with the constraint conditions of the three-dimensional model, and submitting the overlapped constraint conditions to a dynamics simulation engine to improve the bending constraint effect of the three-dimensional model.
The setting of the S4 dynamic attribute depends on the result of the physical simulation effect, any dynamic attribute can be calculated, the operation is empirical, and there is no specific operation, such as air conditioning in summer, how low the operation is, depends on how hot the environment is, what the parameters are adjusted, and depends on the fact that the physical simulation effect is good or bad, and the parameters do not need to be adjusted.
The first embodiment is as follows:
constructing a high-strength bending constraint for a basketball model in animation of shooting of a character by adopting a method for constructing the high-strength bending constraint from a topological relation:
in the CG animation production process, after a person throws a basketball, the basketball enters a frame and falls on the ground, for the action, the basketball needs to pass through a parabola after being thrown to touch a backboard and enter the frame after being collided, falls on the ground and rebounds on the ground for a plurality of times, at this time, the time is long and is not easy to control by using the traditional manpower animation, because the throwing process animation of the basketball is produced by manpower, the position of the ball and the shape of the ball need to be controlled independently at each time point, such as when the ball hits the backboard, what deformation happens to the impact surface, and the like, if the manpower production can be corrected and adjusted only slowly by experience, the time consumption is not necessarily enough to achieve vivid effect, but the throwing track can be automatically calculated by using dynamic calculation under given conditions, such as the coordinates of the hand of the ball, the coordinates of the frame, the impact point of the backboard, and the like, the speed of the motion process, the deformation effect of collision and the like, and the complex animation adjustment one by one time point is omitted.
However, in the manufacturing process, the basketball needs to be subjected to corresponding dynamic constraint setting (such as the softness of the basketball, and the rebound effect of the collision is controlled by the constraint), and if a traditional constraint mode is used, the bending constraint with high hardness is required to be achieved, only a solution process can be replaced, such as FEM simulation or an additional correction process is added after the result of the PBD, so as to ensure that the basketball is not deformed too much, because the basketball is closer to a rigid body rather than a flexible body during the collision (but the flexible body is still deformed at the moment of the collision). Both replacement and addition of correction introduce significant computational effort, and if this requirement is only part of the overall solution process, these additional or replaced steps can be difficult to follow for overall collision or other interaction (e.g., we now need to recreate a dynamic effect that accounts for the basketball, which is not appropriate, and the solution process of replacing only the basketball can result in the basketball not having dynamic interaction with other models solved by the PBD algorithm, such as collision effects).
By adopting the method, starting from each vertex of the basketball, the vertices in all K rings are searched, the constraints of the point and the vertices are added to the model, the parameters of the constraints are set (the range of the parameters of the constraints is determined by a dynamic algorithm and is irrelevant to the construction of the constraints), if the K value is larger, the constraint information contained in each vertex of the basketball is more, so that a stable dynamic local effect is formed from the current vertex to all the vertices in the K rings (because of the mutual constraint effect), and when all the vertices are constructed, the effect range is larger (the larger the K value is, the more the vertices are associated with each vertex is), the constraint effect is stronger in resolving.
All the constraints are constructed from the basketball model and are taken as relevant conditions of dynamics calculation, the relevant conditions are handed to a physical simulation engine together with the model, the physical simulation engine determines how to calculate dynamics simulation effects (parameters comprise the shape of the basketball, the elasticity, the impact effect strength and the like) through the relevant conditions of the dynamics calculation and the parameters of the model, the constraints have higher-strength constraint capacity, a larger effect calculation range can be provided for the physical simulation engine, the basketball does not need to add additional steps to modify the impact effect and the like, the constraint enhancement effect of the method has no upper limit, and all the possible constraints with constraint strength can be provided within the hard range of the physical simulation calculation.
According to the embodiment, the high-strength bending constraint model is directly constructed from the vertex of the vertex k ring on the connected domain, so that the conversion into the traditional algorithm calculation or the addition of a correction program is avoided, and the stability and controllability of effect calculation are ensured. Meanwhile, the constraint strength can be directly modified by controlling the value of k, and more settings for parameters such as bend angle and the like are not needed.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A method of constructing a high-strength bending constraint from topological relations, comprising the steps of:
s1, dividing connected domains of a three-dimensional model to be subjected to dynamic simulation, finding a plurality of different connected domains, and acquiring a geometric body set corresponding to each connected domain;
s2, in the geometry set of each connected domain, sending out from a point, and acquiring all vertexes of the vertexes in the corresponding k rings according to the connection relation between the edges and the faces;
s3, selecting required vertexes from all vertexes of the k ring according to the requirement of calculation accuracy, wherein the selected vertexes comprise k ring boundaries or all vertexes in the k ring, determining constraint conditions of each vertex and the selected vertexes in the k ring, and adding the constraint conditions to the three-dimensional model;
s4, setting dynamic attributes of the constraint conditions, wherein the dynamic attributes comprise static length, elastic attributes and attenuation attributes;
and S5, overlapping the added constraint conditions with the constraint conditions of the three-dimensional model, and submitting the overlapped constraint conditions to a dynamics simulation engine to enhance the bending constraint effect of the three-dimensional model.
2. The method for constructing high-strength bending constraints from topological relations of claim 1, wherein the geometry set of S1 comprises a point set, an edge set and a face set.
3. The method for constructing high-strength bending constraints from topological relations of claim 1, wherein the setting of the S4 dynamic property depends on the result of physical simulation effect.
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