139 lines
3.2 KiB
C++
139 lines
3.2 KiB
C++
/*
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* Copyright (c) 2006-2010 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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#include "Box2D/Collision/Shapes/b2EdgeShape.h"
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#include <new>
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void b2EdgeShape::Set(const b2Vec2& v1, const b2Vec2& v2)
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{
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m_vertex1 = v1;
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m_vertex2 = v2;
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m_hasVertex0 = false;
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m_hasVertex3 = false;
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}
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b2Shape* b2EdgeShape::Clone(b2BlockAllocator* allocator) const
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{
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void* mem = allocator->Allocate(sizeof(b2EdgeShape));
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b2EdgeShape* clone = new (mem) b2EdgeShape;
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*clone = *this;
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return clone;
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}
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int32 b2EdgeShape::GetChildCount() const
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{
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return 1;
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}
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bool b2EdgeShape::TestPoint(const b2Transform& xf, const b2Vec2& p) const
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{
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B2_NOT_USED(xf);
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B2_NOT_USED(p);
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return false;
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}
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// p = p1 + t * d
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// v = v1 + s * e
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// p1 + t * d = v1 + s * e
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// s * e - t * d = p1 - v1
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bool b2EdgeShape::RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
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const b2Transform& xf, int32 childIndex) const
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{
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B2_NOT_USED(childIndex);
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// Put the ray into the edge's frame of reference.
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b2Vec2 p1 = b2MulT(xf.q, input.p1 - xf.p);
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b2Vec2 p2 = b2MulT(xf.q, input.p2 - xf.p);
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b2Vec2 d = p2 - p1;
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b2Vec2 v1 = m_vertex1;
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b2Vec2 v2 = m_vertex2;
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b2Vec2 e = v2 - v1;
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b2Vec2 normal(e.y, -e.x);
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normal.Normalize();
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// q = p1 + t * d
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// dot(normal, q - v1) = 0
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// dot(normal, p1 - v1) + t * dot(normal, d) = 0
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float32 numerator = b2Dot(normal, v1 - p1);
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float32 denominator = b2Dot(normal, d);
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if (denominator == 0.0f)
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{
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return false;
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}
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float32 t = numerator / denominator;
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if (t < 0.0f || input.maxFraction < t)
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{
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return false;
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}
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b2Vec2 q = p1 + t * d;
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// q = v1 + s * r
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// s = dot(q - v1, r) / dot(r, r)
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b2Vec2 r = v2 - v1;
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float32 rr = b2Dot(r, r);
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if (rr == 0.0f)
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{
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return false;
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}
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float32 s = b2Dot(q - v1, r) / rr;
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if (s < 0.0f || 1.0f < s)
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{
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return false;
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}
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output->fraction = t;
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if (numerator > 0.0f)
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{
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output->normal = -b2Mul(xf.q, normal);
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}
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else
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{
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output->normal = b2Mul(xf.q, normal);
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}
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return true;
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}
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void b2EdgeShape::ComputeAABB(b2AABB* aabb, const b2Transform& xf, int32 childIndex) const
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{
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B2_NOT_USED(childIndex);
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b2Vec2 v1 = b2Mul(xf, m_vertex1);
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b2Vec2 v2 = b2Mul(xf, m_vertex2);
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b2Vec2 lower = b2Min(v1, v2);
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b2Vec2 upper = b2Max(v1, v2);
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b2Vec2 r(m_radius, m_radius);
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aabb->lowerBound = lower - r;
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aabb->upperBound = upper + r;
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}
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void b2EdgeShape::ComputeMass(b2MassData* massData, float32 density) const
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{
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B2_NOT_USED(density);
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massData->mass = 0.0f;
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massData->center = 0.5f * (m_vertex1 + m_vertex2);
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massData->I = 0.0f;
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}
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