1 /* 2 * Copyright (c) 2006-2010 Erin Catto http://www.box2d.org 3 * 4 * This software is provided 'as-is', without any express or implied 5 * warranty. In no event will the authors be held liable for any damages 6 * arising from the use of this software. 7 * Permission is granted to anyone to use this software for any purpose, 8 * including commercial applications, and to alter it and redistribute it 9 * freely, subject to the following restrictions: 10 * 1. The origin of this software must not be misrepresented; you must not 11 * claim that you wrote the original software. If you use this software 12 * in a product, an acknowledgment in the product documentation would be 13 * appreciated but is not required. 14 * 2. Altered source versions must be plainly marked as such, and must not be 15 * misrepresented as being the original software. 16 * 3. This notice may not be removed or altered from any source distribution. 17 */ 18 19 #include <Box2D/Collision/Shapes/b2ChainShape.h> 20 #include <Box2D/Collision/Shapes/b2EdgeShape.h> 21 #include <new> 22 #include <cstring> 23 using namespace std; 24 25 b2ChainShape::~b2ChainShape() 26 { 27 Clear(); 28 } 29 30 void b2ChainShape::Clear() 31 { 32 b2Free(m_vertices); 33 m_vertices = NULL; 34 m_count = 0; 35 } 36 37 void b2ChainShape::CreateLoop(const b2Vec2* vertices, int32 count) 38 { 39 b2Assert(m_vertices == NULL && m_count == 0); 40 b2Assert(count >= 3); 41 for (int32 i = 1; i < count; ++i) 42 { 43 b2Vec2 v1 = vertices[i-1]; 44 b2Vec2 v2 = vertices[i]; 45 // If the code crashes here, it means your vertices are too close together. 46 b2Assert(b2DistanceSquared(v1, v2) > b2_linearSlop * b2_linearSlop); 47 } 48 49 m_count = count + 1; 50 m_vertices = (b2Vec2*)b2Alloc(m_count * sizeof(b2Vec2)); 51 memcpy(m_vertices, vertices, count * sizeof(b2Vec2)); 52 m_vertices[count] = m_vertices[0]; 53 m_prevVertex = m_vertices[m_count - 2]; 54 m_nextVertex = m_vertices[1]; 55 m_hasPrevVertex = true; 56 m_hasNextVertex = true; 57 } 58 59 void b2ChainShape::CreateChain(const b2Vec2* vertices, int32 count) 60 { 61 b2Assert(m_vertices == NULL && m_count == 0); 62 b2Assert(count >= 2); 63 for (int32 i = 1; i < count; ++i) 64 { 65 // If the code crashes here, it means your vertices are too close together. 66 b2Assert(b2DistanceSquared(vertices[i-1], vertices[i]) > b2_linearSlop * b2_linearSlop); 67 } 68 69 m_count = count; 70 m_vertices = (b2Vec2*)b2Alloc(count * sizeof(b2Vec2)); 71 memcpy(m_vertices, vertices, m_count * sizeof(b2Vec2)); 72 73 m_hasPrevVertex = false; 74 m_hasNextVertex = false; 75 76 m_prevVertex.SetZero(); 77 m_nextVertex.SetZero(); 78 } 79 80 void b2ChainShape::SetPrevVertex(const b2Vec2& prevVertex) 81 { 82 m_prevVertex = prevVertex; 83 m_hasPrevVertex = true; 84 } 85 86 void b2ChainShape::SetNextVertex(const b2Vec2& nextVertex) 87 { 88 m_nextVertex = nextVertex; 89 m_hasNextVertex = true; 90 } 91 92 b2Shape* b2ChainShape::Clone(b2BlockAllocator* allocator) const 93 { 94 void* mem = allocator->Allocate(sizeof(b2ChainShape)); 95 b2ChainShape* clone = new (mem) b2ChainShape; 96 clone->CreateChain(m_vertices, m_count); 97 clone->m_prevVertex = m_prevVertex; 98 clone->m_nextVertex = m_nextVertex; 99 clone->m_hasPrevVertex = m_hasPrevVertex; 100 clone->m_hasNextVertex = m_hasNextVertex; 101 return clone; 102 } 103 104 int32 b2ChainShape::GetChildCount() const 105 { 106 // edge count = vertex count - 1 107 return m_count - 1; 108 } 109 110 void b2ChainShape::GetChildEdge(b2EdgeShape* edge, int32 index) const 111 { 112 b2Assert(0 <= index && index < m_count - 1); 113 edge->m_type = b2Shape::e_edge; 114 edge->m_radius = m_radius; 115 116 edge->m_vertex1 = m_vertices[index + 0]; 117 edge->m_vertex2 = m_vertices[index + 1]; 118 119 if (index > 0) 120 { 121 edge->m_vertex0 = m_vertices[index - 1]; 122 edge->m_hasVertex0 = true; 123 } 124 else 125 { 126 edge->m_vertex0 = m_prevVertex; 127 edge->m_hasVertex0 = m_hasPrevVertex; 128 } 129 130 if (index < m_count - 2) 131 { 132 edge->m_vertex3 = m_vertices[index + 2]; 133 edge->m_hasVertex3 = true; 134 } 135 else 136 { 137 edge->m_vertex3 = m_nextVertex; 138 edge->m_hasVertex3 = m_hasNextVertex; 139 } 140 } 141 142 bool b2ChainShape::TestPoint(const b2Transform& xf, const b2Vec2& p) const 143 { 144 B2_NOT_USED(xf); 145 B2_NOT_USED(p); 146 return false; 147 } 148 149 bool b2ChainShape::RayCast(b2RayCastOutput* output, const b2RayCastInput& input, 150 const b2Transform& xf, int32 childIndex) const 151 { 152 b2Assert(childIndex < m_count); 153 154 b2EdgeShape edgeShape; 155 156 int32 i1 = childIndex; 157 int32 i2 = childIndex + 1; 158 if (i2 == m_count) 159 { 160 i2 = 0; 161 } 162 163 edgeShape.m_vertex1 = m_vertices[i1]; 164 edgeShape.m_vertex2 = m_vertices[i2]; 165 166 return edgeShape.RayCast(output, input, xf, 0); 167 } 168 169 void b2ChainShape::ComputeAABB(b2AABB* aabb, const b2Transform& xf, int32 childIndex) const 170 { 171 b2Assert(childIndex < m_count); 172 173 int32 i1 = childIndex; 174 int32 i2 = childIndex + 1; 175 if (i2 == m_count) 176 { 177 i2 = 0; 178 } 179 180 b2Vec2 v1 = b2Mul(xf, m_vertices[i1]); 181 b2Vec2 v2 = b2Mul(xf, m_vertices[i2]); 182 183 aabb->lowerBound = b2Min(v1, v2); 184 aabb->upperBound = b2Max(v1, v2); 185 } 186 187 void b2ChainShape::ComputeMass(b2MassData* massData, float32 density) const 188 { 189 B2_NOT_USED(density); 190 191 massData->mass = 0.0f; 192 massData->center.SetZero(); 193 massData->I = 0.0f; 194 } 195
