b2Distance.h
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上传日期:2022-01-07
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- /*
- * Copyright (c) 2006-2009 Erin Catto http://www.gphysics.com
- *
- * This software is provided 'as-is', without any express or implied
- * warranty. In no event will the authors be held liable for any damages
- * arising from the use of this software.
- * Permission is granted to anyone to use this software for any purpose,
- * including commercial applications, and to alter it and redistribute it
- * freely, subject to the following restrictions:
- * 1. The origin of this software must not be misrepresented; you must not
- * claim that you wrote the original software. If you use this software
- * in a product, an acknowledgment in the product documentation would be
- * appreciated but is not required.
- * 2. Altered source versions must be plainly marked as such, and must not be
- * misrepresented as being the original software.
- * 3. This notice may not be removed or altered from any source distribution.
- */
- #ifndef B2_DISTANCE_H
- #define B2_DISTANCE_H
- #include <Box2D/Common/b2Math.h>
- #include <climits>
- class b2Shape;
- /// A distance proxy is used by the GJK algorithm.
- /// It encapsulates any shape.
- struct b2DistanceProxy
- {
- b2DistanceProxy() : m_vertices(NULL), m_count(0), m_radius(0.0f) {}
- /// Initialize the proxy using the given shape. The shape
- /// must remain in scope while the proxy is in use.
- void Set(const b2Shape* shape);
- /// Get the supporting vertex index in the given direction.
- int32 GetSupport(const b2Vec2& d) const;
- /// Get the supporting vertex in the given direction.
- const b2Vec2& GetSupportVertex(const b2Vec2& d) const;
- /// Get the vertex count.
- int32 GetVertexCount() const;
- /// Get a vertex by index. Used by b2Distance.
- const b2Vec2& GetVertex(int32 index) const;
- const b2Vec2* m_vertices;
- int32 m_count;
- float32 m_radius;
- };
- /// Used to warm start b2Distance.
- /// Set count to zero on first call.
- struct b2SimplexCache
- {
- float32 metric; ///< length or area
- uint16 count;
- uint8 indexA[3]; ///< vertices on shape A
- uint8 indexB[3]; ///< vertices on shape B
- };
- /// Input for b2Distance.
- /// You have to option to use the shape radii
- /// in the computation. Even
- struct b2DistanceInput
- {
- b2DistanceProxy proxyA;
- b2DistanceProxy proxyB;
- b2Transform transformA;
- b2Transform transformB;
- bool useRadii;
- };
- /// Output for b2Distance.
- struct b2DistanceOutput
- {
- b2Vec2 pointA; ///< closest point on shapeA
- b2Vec2 pointB; ///< closest point on shapeB
- float32 distance;
- int32 iterations; ///< number of GJK iterations used
- };
- /// Compute the closest points between two shapes. Supports any combination of:
- /// b2CircleShape, b2PolygonShape, b2EdgeShape. The simplex cache is input/output.
- /// On the first call set b2SimplexCache.count to zero.
- void b2Distance(b2DistanceOutput* output,
- b2SimplexCache* cache,
- const b2DistanceInput* input);
- //////////////////////////////////////////////////////////////////////////
- inline int32 b2DistanceProxy::GetVertexCount() const
- {
- return m_count;
- }
- inline const b2Vec2& b2DistanceProxy::GetVertex(int32 index) const
- {
- b2Assert(0 <= index && index < m_count);
- return m_vertices[index];
- }
- inline int32 b2DistanceProxy::GetSupport(const b2Vec2& d) const
- {
- int32 bestIndex = 0;
- float32 bestValue = b2Dot(m_vertices[0], d);
- for (int32 i = 1; i < m_count; ++i)
- {
- float32 value = b2Dot(m_vertices[i], d);
- if (value > bestValue)
- {
- bestIndex = i;
- bestValue = value;
- }
- }
- return bestIndex;
- }
- inline const b2Vec2& b2DistanceProxy::GetSupportVertex(const b2Vec2& d) const
- {
- int32 bestIndex = 0;
- float32 bestValue = b2Dot(m_vertices[0], d);
- for (int32 i = 1; i < m_count; ++i)
- {
- float32 value = b2Dot(m_vertices[i], d);
- if (value > bestValue)
- {
- bestIndex = i;
- bestValue = value;
- }
- }
- return m_vertices[bestIndex];
- }
- #endif