167 lines
4.4 KiB
C++
167 lines
4.4 KiB
C++
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/*
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* Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef B2_DISTANCE_H
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#define B2_DISTANCE_H
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#include "Box2D/Common/b2Math.h"
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class b2Shape;
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/// A distance proxy is used by the GJK algorithm.
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/// It encapsulates any shape.
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struct b2DistanceProxy
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{
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b2DistanceProxy() : m_vertices(nullptr), m_count(0), m_radius(0.0f) {}
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/// Initialize the proxy using the given shape. The shape
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/// must remain in scope while the proxy is in use.
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void Set(const b2Shape* shape, int32 index);
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/// Initialize the proxy using a vertex cloud and radius. The vertices
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/// must remain in scope while the proxy is in use.
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void Set(const b2Vec2* vertices, int32 count, float32 radius);
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/// Get the supporting vertex index in the given direction.
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int32 GetSupport(const b2Vec2& d) const;
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/// Get the supporting vertex in the given direction.
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const b2Vec2& GetSupportVertex(const b2Vec2& d) const;
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/// Get the vertex count.
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int32 GetVertexCount() const;
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/// Get a vertex by index. Used by b2Distance.
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const b2Vec2& GetVertex(int32 index) const;
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b2Vec2 m_buffer[2];
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const b2Vec2* m_vertices;
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int32 m_count;
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float32 m_radius;
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};
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/// Used to warm start b2Distance.
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/// Set count to zero on first call.
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struct b2SimplexCache
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{
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float32 metric; ///< length or area
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uint16 count;
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uint8 indexA[3]; ///< vertices on shape A
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uint8 indexB[3]; ///< vertices on shape B
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};
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/// Input for b2Distance.
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/// You have to option to use the shape radii
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/// in the computation. Even
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struct b2DistanceInput
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{
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b2DistanceProxy proxyA;
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b2DistanceProxy proxyB;
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b2Transform transformA;
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b2Transform transformB;
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bool useRadii;
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};
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/// Output for b2Distance.
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struct b2DistanceOutput
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{
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b2Vec2 pointA; ///< closest point on shapeA
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b2Vec2 pointB; ///< closest point on shapeB
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float32 distance;
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int32 iterations; ///< number of GJK iterations used
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};
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/// Compute the closest points between two shapes. Supports any combination of:
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/// b2CircleShape, b2PolygonShape, b2EdgeShape. The simplex cache is input/output.
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/// On the first call set b2SimplexCache.count to zero.
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void b2Distance(b2DistanceOutput* output,
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b2SimplexCache* cache,
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const b2DistanceInput* input);
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/// Input parameters for b2ShapeCast
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struct b2ShapeCastInput
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{
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b2DistanceProxy proxyA;
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b2DistanceProxy proxyB;
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b2Transform transformA;
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b2Transform transformB;
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b2Vec2 translationB;
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};
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/// Output results for b2ShapeCast
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struct b2ShapeCastOutput
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{
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b2Vec2 point;
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b2Vec2 normal;
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float32 lambda;
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int32 iterations;
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};
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/// Perform a linear shape cast of shape B moving and shape A fixed. Determines the hit point, normal, and translation fraction.
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bool b2ShapeCast(b2ShapeCastOutput* output, const b2ShapeCastInput* input);
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//////////////////////////////////////////////////////////////////////////
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inline int32 b2DistanceProxy::GetVertexCount() const
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{
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return m_count;
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}
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inline const b2Vec2& b2DistanceProxy::GetVertex(int32 index) const
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{
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b2Assert(0 <= index && index < m_count);
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return m_vertices[index];
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}
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inline int32 b2DistanceProxy::GetSupport(const b2Vec2& d) const
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{
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int32 bestIndex = 0;
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float32 bestValue = b2Dot(m_vertices[0], d);
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for (int32 i = 1; i < m_count; ++i)
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{
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float32 value = b2Dot(m_vertices[i], d);
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if (value > bestValue)
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{
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bestIndex = i;
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bestValue = value;
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}
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}
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return bestIndex;
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}
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inline const b2Vec2& b2DistanceProxy::GetSupportVertex(const b2Vec2& d) const
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{
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int32 bestIndex = 0;
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float32 bestValue = b2Dot(m_vertices[0], d);
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for (int32 i = 1; i < m_count; ++i)
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{
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float32 value = b2Dot(m_vertices[i], d);
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if (value > bestValue)
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{
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bestIndex = i;
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bestValue = value;
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}
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}
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return m_vertices[bestIndex];
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}
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#endif
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