axmol/Box2D/Collision/Shapes/b2ChainShape.cpp

/*
* Copyright (c) 2006-2010 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.
*/

#include <Box2D/Collision/Shapes/b2ChainShape.h>
#include <Box2D/Collision/Shapes/b2EdgeShape.h>
#include <new>
#include <cstring>
using namespace std;

b2ChainShape::~b2ChainShape()
{
    b2Free(m_vertices);
    m_vertices = NULL;
    m_count = 0;
}

void b2ChainShape::CreateLoop(const b2Vec2* vertices, int32 count)
{
    b2Assert(m_vertices == NULL && m_count == 0);
    b2Assert(count >= 3);
    m_count = count + 1;
    m_vertices = (b2Vec2*)b2Alloc(m_count * sizeof(b2Vec2));
    memcpy(m_vertices, vertices, count * sizeof(b2Vec2));
    m_vertices[count] = m_vertices[0];
    m_prevVertex = m_vertices[m_count - 2];
    m_nextVertex = m_vertices[1];
    m_hasPrevVertex = true;
    m_hasNextVertex = true;
}

void b2ChainShape::CreateChain(const b2Vec2* vertices, int32 count)
{
    b2Assert(m_vertices == NULL && m_count == 0);
    b2Assert(count >= 2);
    m_count = count;
    m_vertices = (b2Vec2*)b2Alloc(count * sizeof(b2Vec2));
    memcpy(m_vertices, vertices, m_count * sizeof(b2Vec2));
    m_hasPrevVertex = false;
    m_hasNextVertex = false;
}

void b2ChainShape::SetPrevVertex(const b2Vec2& prevVertex)
{
    m_prevVertex = prevVertex;
    m_hasPrevVertex = true;
}

void b2ChainShape::SetNextVertex(const b2Vec2& nextVertex)
{
    m_nextVertex = nextVertex;
    m_hasNextVertex = true;
}

b2Shape* b2ChainShape::Clone(b2BlockAllocator* allocator) const
{
    void* mem = allocator->Allocate(sizeof(b2ChainShape));
    b2ChainShape* clone = new (mem) b2ChainShape;
    clone->CreateChain(m_vertices, m_count);
    clone->m_prevVertex = m_prevVertex;
    clone->m_nextVertex = m_nextVertex;
    clone->m_hasPrevVertex = m_hasPrevVertex;
    clone->m_hasNextVertex = m_hasNextVertex;
    return clone;
}

int32 b2ChainShape::GetChildCount() const
{
    // edge count = vertex count - 1
    return m_count - 1;
}

void b2ChainShape::GetChildEdge(b2EdgeShape* edge, int32 index) const
{
    b2Assert(0 <= index && index < m_count - 1);
    edge->m_type = b2Shape::e_edge;
    edge->m_radius = m_radius;

    edge->m_vertex1 = m_vertices[index + 0];
    edge->m_vertex2 = m_vertices[index + 1];

    if (index > 0)
    {
        edge->m_vertex0 = m_vertices[index - 1];
        edge->m_hasVertex0 = true;
    }
    else
    {
        edge->m_vertex0 = m_prevVertex;
        edge->m_hasVertex0 = m_hasPrevVertex;
    }

    if (index < m_count - 2)
    {
        edge->m_vertex3 = m_vertices[index + 2];
        edge->m_hasVertex3 = true;
    }
    else
    {
        edge->m_vertex3 = m_nextVertex;
        edge->m_hasVertex3 = m_hasNextVertex;
    }
}

bool b2ChainShape::TestPoint(const b2Transform& xf, const b2Vec2& p) const
{
    B2_NOT_USED(xf);
    B2_NOT_USED(p);
    return false;
}

bool b2ChainShape::RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
                            const b2Transform& xf, int32 childIndex) const
{
    b2Assert(childIndex < m_count);

    b2EdgeShape edgeShape;

    int32 i1 = childIndex;
    int32 i2 = childIndex + 1;
    if (i2 == m_count)
    {
        i2 = 0;
    }

    edgeShape.m_vertex1 = m_vertices[i1];
    edgeShape.m_vertex2 = m_vertices[i2];

    return edgeShape.RayCast(output, input, xf, 0);
}

void b2ChainShape::ComputeAABB(b2AABB* aabb, const b2Transform& xf, int32 childIndex) const
{
    b2Assert(childIndex < m_count);

    int32 i1 = childIndex;
    int32 i2 = childIndex + 1;
    if (i2 == m_count)
    {
        i2 = 0;
    }

    b2Vec2 v1 = b2Mul(xf, m_vertices[i1]);
    b2Vec2 v2 = b2Mul(xf, m_vertices[i2]);

    aabb->lowerBound = b2Min(v1, v2);
    aabb->upperBound = b2Max(v1, v2);
}

void b2ChainShape::ComputeMass(b2MassData* massData, float32 density) const
{
    B2_NOT_USED(density);

    massData->mass = 0.0f;
    massData->center.SetZero();
    massData->I = 0.0f;
}