File indexing completed on 2024-05-19 14:56:21

 
 /*
 * Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
 *
 * 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>
 
 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, int32 index);
 
     /// 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;
 
     b2Vec2 m_buffer[2];
     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