91 lines
3 KiB
C++
91 lines
3 KiB
C++
// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
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// SPDX-FileCopyrightText: 2024 Jorrit Rouwe
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <Jolt/Physics/Collision/CollideSoftBodyVertexIterator.h>
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#include <Jolt/Geometry/ClosestPoint.h>
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JPH_NAMESPACE_BEGIN
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/// Collision detection helper that collides soft body vertices vs triangles
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class JPH_EXPORT CollideSoftBodyVerticesVsTriangles
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{
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public:
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CollideSoftBodyVerticesVsTriangles(Mat44Arg inCenterOfMassTransform, Vec3Arg inScale) :
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mTransform(inCenterOfMassTransform * Mat44::sScale(inScale)),
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mInvTransform(mTransform.Inversed()),
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mNormalSign(ScaleHelpers::IsInsideOut(inScale)? -1.0f : 1.0f)
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{
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}
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JPH_INLINE void StartVertex(const CollideSoftBodyVertexIterator &inVertex)
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{
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mLocalPosition = mInvTransform * inVertex.GetPosition();
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mClosestDistanceSq = FLT_MAX;
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}
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JPH_INLINE void ProcessTriangle(Vec3Arg inV0, Vec3Arg inV1, Vec3Arg inV2)
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{
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// Get the closest point from the vertex to the triangle
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uint32 set;
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Vec3 closest_point = ClosestPoint::GetClosestPointOnTriangle(inV0 - mLocalPosition, inV1 - mLocalPosition, inV2 - mLocalPosition, set);
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float dist_sq = closest_point.LengthSq();
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if (dist_sq < mClosestDistanceSq)
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{
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mV0 = inV0;
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mV1 = inV1;
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mV2 = inV2;
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mClosestPoint = closest_point;
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mClosestDistanceSq = dist_sq;
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mSet = set;
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}
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}
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JPH_INLINE void FinishVertex(const CollideSoftBodyVertexIterator &ioVertex, int inCollidingShapeIndex) const
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{
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if (mClosestDistanceSq < FLT_MAX)
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{
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// Convert triangle to world space
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Vec3 v0 = mTransform * mV0;
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Vec3 v1 = mTransform * mV1;
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Vec3 v2 = mTransform * mV2;
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Vec3 triangle_normal = mNormalSign * (v1 - v0).Cross(v2 - v0).NormalizedOr(Vec3::sAxisY());
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if (mSet == 0b111)
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{
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// Closest is interior to the triangle, use plane as collision plane but don't allow more than 0.1 m penetration
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// because otherwise a triangle half a level a way will have a huge penetration if it is back facing
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float penetration = min(triangle_normal.Dot(v0 - ioVertex.GetPosition()), 0.1f);
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if (ioVertex.UpdatePenetration(penetration))
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ioVertex.SetCollision(Plane::sFromPointAndNormal(v0, triangle_normal), inCollidingShapeIndex);
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}
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else
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{
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// Closest point is on an edge or vertex, use closest point as collision plane
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Vec3 closest_point = mTransform * (mLocalPosition + mClosestPoint);
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Vec3 normal = ioVertex.GetPosition() - closest_point;
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if (normal.Dot(triangle_normal) > 0.0f) // Ignore back facing edges
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{
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float normal_length = normal.Length();
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float penetration = -normal_length;
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if (ioVertex.UpdatePenetration(penetration))
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ioVertex.SetCollision(Plane::sFromPointAndNormal(closest_point, normal_length > 0.0f? normal / normal_length : triangle_normal), inCollidingShapeIndex);
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}
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}
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}
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}
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Mat44 mTransform;
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Mat44 mInvTransform;
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Vec3 mLocalPosition;
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Vec3 mV0, mV1, mV2;
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Vec3 mClosestPoint;
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float mNormalSign;
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float mClosestDistanceSq;
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uint32 mSet;
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};
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JPH_NAMESPACE_END
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