File indexing completed on 2025-02-16 03:29:32

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