paulxstretch/deps/juce/modules/juce_box2d/box2d/Collision/b2CollidePolygon.cpp
essej 25bd5d8adb git subrepo clone --branch=sono6good https://github.com/essej/JUCE.git deps/juce
subrepo:
  subdir:   "deps/juce"
  merged:   "b13f9084e"
upstream:
  origin:   "https://github.com/essej/JUCE.git"
  branch:   "sono6good"
  commit:   "b13f9084e"
git-subrepo:
  version:  "0.4.3"
  origin:   "https://github.com/ingydotnet/git-subrepo.git"
  commit:   "2f68596"
2022-04-18 17:51:22 -04:00

318 lines
8.8 KiB
C++

/*
* 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 "b2Collision.h"
#include "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;
}