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/*
* 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(nullptr), 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);
/// Initialize the proxy using a vertex cloud and radius. The vertices
/// must remain in scope while the proxy is in use.
void Set(const b2Vec2* vertices, int32 count, float32 radius);
/// 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);
/// Input parameters for b2ShapeCast
struct b2ShapeCastInput
{
b2DistanceProxy proxyA;
b2DistanceProxy proxyB;
b2Transform transformA;
b2Transform transformB;
b2Vec2 translationB;
};
/// Output results for b2ShapeCast
struct b2ShapeCastOutput
{
b2Vec2 point;
b2Vec2 normal;
float32 lambda;
int32 iterations;
};
/// Perform a linear shape cast of shape B moving and shape A fixed. Determines the hit point, normal, and translation fraction.
bool b2ShapeCast(b2ShapeCastOutput* output, const b2ShapeCastInput* 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
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