b2Collision.h

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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_COLLISION_H
#define B2_COLLISION_H

#include <Box2D/Common/b2Math.h>
#include <limits.h>


class b2Shape;
class b2CircleShape;
class b2EdgeShape;
class b2PolygonShape;

const uint8 b2_nullFeature = UCHAR_MAX;

struct b2ContactFeature
{
    enum Type
    {
        e_vertex = 0,
        e_face = 1
    };

    uint8 indexA;       
    uint8 indexB;       
    uint8 typeA;        
    uint8 typeB;        
};

union b2ContactID
{
    b2ContactFeature cf;
    uint32 key;                 
};

struct b2ManifoldPoint
{
    b2Vec2 localPoint;      
    float32 normalImpulse;  
    float32 tangentImpulse; 
    b2ContactID id;         
};

struct b2Manifold
{
    enum Type
    {
        e_circles,
        e_faceA,
        e_faceB
    };

    b2ManifoldPoint points[b2_maxManifoldPoints];   
    b2Vec2 localNormal;                             
    b2Vec2 localPoint;                              
    Type type;
    int32 pointCount;                               
};

struct b2WorldManifold
{
    void Initialize(const b2Manifold* manifold,
                    const b2Transform& xfA, float32 radiusA,
                    const b2Transform& xfB, float32 radiusB);

    b2Vec2 normal;                              
    b2Vec2 points[b2_maxManifoldPoints];        
    float32 separations[b2_maxManifoldPoints];  
};

enum b2PointState
{
    b2_nullState,       
    b2_addState,        
    b2_persistState,    
    b2_removeState      
};

void b2GetPointStates(b2PointState state1[b2_maxManifoldPoints], b2PointState state2[b2_maxManifoldPoints],
                      const b2Manifold* manifold1, const b2Manifold* manifold2);

struct b2ClipVertex
{
    b2Vec2 v;
    b2ContactID id;
};

struct b2RayCastInput
{
    b2Vec2 p1, p2;
    float32 maxFraction;
};

struct b2RayCastOutput
{
    b2Vec2 normal;
    float32 fraction;
};

struct b2AABB
{
    bool IsValid() const;

    b2Vec2 GetCenter() const
    {
        return 0.5f * (lowerBound + upperBound);
    }

    b2Vec2 GetExtents() const
    {
        return 0.5f * (upperBound - lowerBound);
    }

    float32 GetPerimeter() const
    {
        float32 wx = upperBound.x - lowerBound.x;
        float32 wy = upperBound.y - lowerBound.y;
        return 2.0f * (wx + wy);
    }

    void Combine(const b2AABB& aabb)
    {
        lowerBound = b2Min(lowerBound, aabb.lowerBound);
        upperBound = b2Max(upperBound, aabb.upperBound);
    }

    void Combine(const b2AABB& aabb1, const b2AABB& aabb2)
    {
        lowerBound = b2Min(aabb1.lowerBound, aabb2.lowerBound);
        upperBound = b2Max(aabb1.upperBound, aabb2.upperBound);
    }

    bool Contains(const b2AABB& aabb) const
    {
        bool result = true;
        result = result && lowerBound.x <= aabb.lowerBound.x;
        result = result && lowerBound.y <= aabb.lowerBound.y;
        result = result && aabb.upperBound.x <= upperBound.x;
        result = result && aabb.upperBound.y <= upperBound.y;
        return result;
    }

    bool RayCast(b2RayCastOutput* output, const b2RayCastInput& input) const;

    b2Vec2 lowerBound;  
    b2Vec2 upperBound;  
};

void b2CollideCircles(b2Manifold* manifold,
                      const b2CircleShape* circleA, const b2Transform& xfA,
                      const b2CircleShape* circleB, const b2Transform& xfB);

void b2CollidePolygonAndCircle(b2Manifold* manifold,
                               const b2PolygonShape* polygonA, const b2Transform& xfA,
                               const b2CircleShape* circleB, const b2Transform& xfB);

void b2CollidePolygons(b2Manifold* manifold,
                       const b2PolygonShape* polygonA, const b2Transform& xfA,
                       const b2PolygonShape* polygonB, const b2Transform& xfB);

void b2CollideEdgeAndCircle(b2Manifold* manifold,
                               const b2EdgeShape* polygonA, const b2Transform& xfA,
                               const b2CircleShape* circleB, const b2Transform& xfB);

void b2CollideEdgeAndPolygon(b2Manifold* manifold,
                               const b2EdgeShape* edgeA, const b2Transform& xfA,
                               const b2PolygonShape* circleB, const b2Transform& xfB);

int32 b2ClipSegmentToLine(b2ClipVertex vOut[2], const b2ClipVertex vIn[2],
                            const b2Vec2& normal, float32 offset, int32 vertexIndexA);

bool b2TestOverlap( const b2Shape* shapeA, int32 indexA,
                    const b2Shape* shapeB, int32 indexB,
                    const b2Transform& xfA, const b2Transform& xfB);

// ---------------- Inline Functions ------------------------------------------

inline bool b2AABB::IsValid() const
{
    b2Vec2 d = upperBound - lowerBound;
    bool valid = d.x >= 0.0f && d.y >= 0.0f;
    valid = valid && lowerBound.IsValid() && upperBound.IsValid();
    return valid;
}

inline bool b2TestOverlap(const b2AABB& a, const b2AABB& b)
{
    b2Vec2 d1, d2;
    d1 = b.lowerBound - a.upperBound;
    d2 = a.lowerBound - b.upperBound;

    if (d1.x > 0.0f || d1.y > 0.0f)
        return false;

    if (d2.x > 0.0f || d2.y > 0.0f)
        return false;

    return true;
}

#endif