Warning, file /education/gcompris/external/qml-box2d/Box2D/Collision/b2CollidePolygon.cpp was not indexed or was modified since last indexation (in which case cross-reference links may be missing, inaccurate or erroneous).

 /*
 * 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 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_count;
     int32 count2 = poly2->m_count;
     const b2Vec2* n1s = poly1->m_normals;
     const b2Vec2* v1s = poly1->m_vertices;
     const b2Vec2* v2s = poly2->m_vertices;
     b2Transform xf = b2MulT(xf2, xf1);
 
     int32 bestIndex = 0;
     float32 maxSeparation = -b2_maxFloat;
     for (int32 i = 0; i < count1; ++i)
     {
         // Get poly1 normal in frame2.
         b2Vec2 n = b2Mul(xf.q, n1s[i]);
         b2Vec2 v1 = b2Mul(xf, v1s[i]);
 
         // Find deepest point for normal i.
         float32 si = b2_maxFloat;
         for (int32 j = 0; j < count2; ++j)
         {
             float32 sij = b2Dot(n, v2s[j] - v1);
             if (sij < si)
             {
                 si = sij;
             }
         }
 
         if (si > maxSeparation)
         {
             maxSeparation = si;
             bestIndex = i;
         }
     }
 
     *edgeIndex = bestIndex;
     return maxSeparation;
 }
 
 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_count;
     const b2Vec2* vertices2 = poly2->m_vertices;
     const b2Vec2* normals2 = poly2->m_normals;
 
     b2Assert(0 <= edge1 && edge1 < poly1->m_count);
 
     // 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_tol = 0.1f * b2_linearSlop;
 
     if (separationB > separationA + k_tol)
     {
         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_count;
     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;
 }