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Diffstat (limited to 'tests/box2d/Box2D/Collision/b2CollidePolygon.cpp')
| -rwxr-xr-x | tests/box2d/Box2D/Collision/b2CollidePolygon.cpp | 317 |
1 files changed, 317 insertions, 0 deletions
diff --git a/tests/box2d/Box2D/Collision/b2CollidePolygon.cpp b/tests/box2d/Box2D/Collision/b2CollidePolygon.cpp new file mode 100755 index 00000000..2f0946b9 --- /dev/null +++ b/tests/box2d/Box2D/Collision/b2CollidePolygon.cpp @@ -0,0 +1,317 @@ +/*
+* 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.
+*/
+
+#include <Box2D/Collision/b2Collision.h>
+#include <Box2D/Collision/Shapes/b2PolygonShape.h>
+
+// Find the separation between poly1 and poly2 for a give edge normal on poly1.
+static float32 b2EdgeSeparation(const b2PolygonShape* poly1, const b2Transform& xf1, int32 edge1,
+ const b2PolygonShape* poly2, const b2Transform& xf2)
+{
+ const b2Vec2* vertices1 = poly1->m_vertices;
+ const b2Vec2* normals1 = poly1->m_normals;
+
+ int32 count2 = poly2->m_vertexCount;
+ const b2Vec2* vertices2 = poly2->m_vertices;
+
+ b2Assert(0 <= edge1 && edge1 < poly1->m_vertexCount);
+
+ // Convert normal from poly1's frame into poly2's frame.
+ b2Vec2 normal1World = b2Mul(xf1.q, normals1[edge1]);
+ b2Vec2 normal1 = b2MulT(xf2.q, normal1World);
+
+ // Find support vertex on poly2 for -normal.
+ int32 index = 0;
+ float32 minDot = b2_maxFloat;
+
+ for (int32 i = 0; i < count2; ++i)
+ {
+ float32 dot = b2Dot(vertices2[i], normal1);
+ if (dot < minDot)
+ {
+ minDot = dot;
+ index = i;
+ }
+ }
+
+ b2Vec2 v1 = b2Mul(xf1, vertices1[edge1]);
+ b2Vec2 v2 = b2Mul(xf2, vertices2[index]);
+ float32 separation = b2Dot(v2 - v1, normal1World);
+ return separation;
+}
+
+// Find the max separation between poly1 and poly2 using edge normals from poly1.
+static float32 b2FindMaxSeparation(int32* edgeIndex,
+ const b2PolygonShape* poly1, const b2Transform& xf1,
+ const b2PolygonShape* poly2, const b2Transform& xf2)
+{
+ int32 count1 = poly1->m_vertexCount;
+ const b2Vec2* normals1 = poly1->m_normals;
+
+ // Vector pointing from the centroid of poly1 to the centroid of poly2.
+ b2Vec2 d = b2Mul(xf2, poly2->m_centroid) - b2Mul(xf1, poly1->m_centroid);
+ b2Vec2 dLocal1 = b2MulT(xf1.q, d);
+
+ // Find edge normal on poly1 that has the largest projection onto d.
+ int32 edge = 0;
+ float32 maxDot = -b2_maxFloat;
+ for (int32 i = 0; i < count1; ++i)
+ {
+ float32 dot = b2Dot(normals1[i], dLocal1);
+ if (dot > maxDot)
+ {
+ maxDot = dot;
+ edge = i;
+ }
+ }
+
+ // Get the separation for the edge normal.
+ float32 s = b2EdgeSeparation(poly1, xf1, edge, poly2, xf2);
+
+ // Check the separation for the previous edge normal.
+ int32 prevEdge = edge - 1 >= 0 ? edge - 1 : count1 - 1;
+ float32 sPrev = b2EdgeSeparation(poly1, xf1, prevEdge, poly2, xf2);
+
+ // Check the separation for the next edge normal.
+ int32 nextEdge = edge + 1 < count1 ? edge + 1 : 0;
+ float32 sNext = b2EdgeSeparation(poly1, xf1, nextEdge, poly2, xf2);
+
+ // Find the best edge and the search direction.
+ int32 bestEdge;
+ float32 bestSeparation;
+ int32 increment;
+ if (sPrev > s && sPrev > sNext)
+ {
+ increment = -1;
+ bestEdge = prevEdge;
+ bestSeparation = sPrev;
+ }
+ else if (sNext > s)
+ {
+ increment = 1;
+ bestEdge = nextEdge;
+ bestSeparation = sNext;
+ }
+ else
+ {
+ *edgeIndex = edge;
+ return s;
+ }
+
+ // Perform a local search for the best edge normal.
+ for ( ; ; )
+ {
+ if (increment == -1)
+ edge = bestEdge - 1 >= 0 ? bestEdge - 1 : count1 - 1;
+ else
+ edge = bestEdge + 1 < count1 ? bestEdge + 1 : 0;
+
+ s = b2EdgeSeparation(poly1, xf1, edge, poly2, xf2);
+
+ if (s > bestSeparation)
+ {
+ bestEdge = edge;
+ bestSeparation = s;
+ }
+ else
+ {
+ break;
+ }
+ }
+
+ *edgeIndex = bestEdge;
+ return bestSeparation;
+}
+
+static void b2FindIncidentEdge(b2ClipVertex c[2],
+ const b2PolygonShape* poly1, const b2Transform& xf1, int32 edge1,
+ const b2PolygonShape* poly2, const b2Transform& xf2)
+{
+ const b2Vec2* normals1 = poly1->m_normals;
+
+ int32 count2 = poly2->m_vertexCount;
+ const b2Vec2* vertices2 = poly2->m_vertices;
+ const b2Vec2* normals2 = poly2->m_normals;
+
+ b2Assert(0 <= edge1 && edge1 < poly1->m_vertexCount);
+
+ // Get the normal of the reference edge in poly2's frame.
+ b2Vec2 normal1 = b2MulT(xf2.q, b2Mul(xf1.q, normals1[edge1]));
+
+ // Find the incident edge on poly2.
+ int32 index = 0;
+ float32 minDot = b2_maxFloat;
+ for (int32 i = 0; i < count2; ++i)
+ {
+ float32 dot = b2Dot(normal1, normals2[i]);
+ if (dot < minDot)
+ {
+ minDot = dot;
+ index = i;
+ }
+ }
+
+ // Build the clip vertices for the incident edge.
+ int32 i1 = index;
+ int32 i2 = i1 + 1 < count2 ? i1 + 1 : 0;
+
+ c[0].v = b2Mul(xf2, vertices2[i1]);
+ c[0].id.cf.indexA = (uint8)edge1;
+ c[0].id.cf.indexB = (uint8)i1;
+ c[0].id.cf.typeA = b2ContactFeature::e_face;
+ c[0].id.cf.typeB = b2ContactFeature::e_vertex;
+
+ c[1].v = b2Mul(xf2, vertices2[i2]);
+ c[1].id.cf.indexA = (uint8)edge1;
+ c[1].id.cf.indexB = (uint8)i2;
+ c[1].id.cf.typeA = b2ContactFeature::e_face;
+ c[1].id.cf.typeB = b2ContactFeature::e_vertex;
+}
+
+// Find edge normal of max separation on A - return if separating axis is found
+// Find edge normal of max separation on B - return if separation axis is found
+// Choose reference edge as min(minA, minB)
+// Find incident edge
+// Clip
+
+// The normal points from 1 to 2
+void b2CollidePolygons(b2Manifold* manifold,
+ const b2PolygonShape* polyA, const b2Transform& xfA,
+ const b2PolygonShape* polyB, const b2Transform& xfB)
+{
+ manifold->pointCount = 0;
+ float32 totalRadius = polyA->m_radius + polyB->m_radius;
+
+ int32 edgeA = 0;
+ float32 separationA = b2FindMaxSeparation(&edgeA, polyA, xfA, polyB, xfB);
+ if (separationA > totalRadius)
+ return;
+
+ int32 edgeB = 0;
+ float32 separationB = b2FindMaxSeparation(&edgeB, polyB, xfB, polyA, xfA);
+ if (separationB > totalRadius)
+ return;
+
+ const b2PolygonShape* poly1; // reference polygon
+ const b2PolygonShape* poly2; // incident polygon
+ b2Transform xf1, xf2;
+ int32 edge1; // reference edge
+ uint8 flip;
+ const float32 k_relativeTol = 0.98f;
+ const float32 k_absoluteTol = 0.001f;
+
+ if (separationB > k_relativeTol * separationA + k_absoluteTol)
+ {
+ poly1 = polyB;
+ poly2 = polyA;
+ xf1 = xfB;
+ xf2 = xfA;
+ edge1 = edgeB;
+ manifold->type = b2Manifold::e_faceB;
+ flip = 1;
+ }
+ else
+ {
+ poly1 = polyA;
+ poly2 = polyB;
+ xf1 = xfA;
+ xf2 = xfB;
+ edge1 = edgeA;
+ manifold->type = b2Manifold::e_faceA;
+ flip = 0;
+ }
+
+ b2ClipVertex incidentEdge[2];
+ b2FindIncidentEdge(incidentEdge, poly1, xf1, edge1, poly2, xf2);
+
+ int32 count1 = poly1->m_vertexCount;
+ const b2Vec2* vertices1 = poly1->m_vertices;
+
+ int32 iv1 = edge1;
+ int32 iv2 = edge1 + 1 < count1 ? edge1 + 1 : 0;
+
+ b2Vec2 v11 = vertices1[iv1];
+ b2Vec2 v12 = vertices1[iv2];
+
+ b2Vec2 localTangent = v12 - v11;
+ localTangent.Normalize();
+
+ b2Vec2 localNormal = b2Cross(localTangent, 1.0f);
+ b2Vec2 planePoint = 0.5f * (v11 + v12);
+
+ b2Vec2 tangent = b2Mul(xf1.q, localTangent);
+ b2Vec2 normal = b2Cross(tangent, 1.0f);
+
+ v11 = b2Mul(xf1, v11);
+ v12 = b2Mul(xf1, v12);
+
+ // Face offset.
+ float32 frontOffset = b2Dot(normal, v11);
+
+ // Side offsets, extended by polytope skin thickness.
+ float32 sideOffset1 = -b2Dot(tangent, v11) + totalRadius;
+ float32 sideOffset2 = b2Dot(tangent, v12) + totalRadius;
+
+ // Clip incident edge against extruded edge1 side edges.
+ b2ClipVertex clipPoints1[2];
+ b2ClipVertex clipPoints2[2];
+ int np;
+
+ // Clip to box side 1
+ np = b2ClipSegmentToLine(clipPoints1, incidentEdge, -tangent, sideOffset1, iv1);
+
+ if (np < 2)
+ return;
+
+ // Clip to negative box side 1
+ np = b2ClipSegmentToLine(clipPoints2, clipPoints1, tangent, sideOffset2, iv2);
+
+ if (np < 2)
+ {
+ return;
+ }
+
+ // Now clipPoints2 contains the clipped points.
+ manifold->localNormal = localNormal;
+ manifold->localPoint = planePoint;
+
+ int32 pointCount = 0;
+ for (int32 i = 0; i < b2_maxManifoldPoints; ++i)
+ {
+ float32 separation = b2Dot(normal, clipPoints2[i].v) - frontOffset;
+
+ if (separation <= totalRadius)
+ {
+ b2ManifoldPoint* cp = manifold->points + pointCount;
+ cp->localPoint = b2MulT(xf2, clipPoints2[i].v);
+ cp->id = clipPoints2[i].id;
+ if (flip)
+ {
+ // Swap features
+ b2ContactFeature cf = cp->id.cf;
+ cp->id.cf.indexA = cf.indexB;
+ cp->id.cf.indexB = cf.indexA;
+ cp->id.cf.typeA = cf.typeB;
+ cp->id.cf.typeB = cf.typeA;
+ }
+ ++pointCount;
+ }
+ }
+
+ manifold->pointCount = pointCount;
+}
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