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// MIT License
// Copyright (c) 2019 Erin Catto
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
#include "box2d/b2_collision.h"
#include "box2d/b2_circle_shape.h"
#include "box2d/b2_polygon_shape.h"
void b2CollideCircles(
b2Manifold* manifold,
const b2CircleShape* circleA, const b2Transform& xfA,
const b2CircleShape* circleB, const b2Transform& xfB)
{
manifold->pointCount = 0;
b2Vec2 pA = b2Mul(xfA, circleA->m_p);
b2Vec2 pB = b2Mul(xfB, circleB->m_p);
b2Vec2 d = pB - pA;
float distSqr = b2Dot(d, d);
float rA = circleA->m_radius, rB = circleB->m_radius;
float radius = rA + rB;
if (distSqr > radius * radius)
{
return;
}
manifold->type = b2Manifold::e_circles;
manifold->localPoint = circleA->m_p;
manifold->localNormal.SetZero();
manifold->pointCount = 1;
manifold->points[0].localPoint = circleB->m_p;
manifold->points[0].id.key = 0;
}
void b2CollidePolygonAndCircle(
b2Manifold* manifold,
const b2PolygonShape* polygonA, const b2Transform& xfA,
const b2CircleShape* circleB, const b2Transform& xfB)
{
manifold->pointCount = 0;
// Compute circle position in the frame of the polygon.
b2Vec2 c = b2Mul(xfB, circleB->m_p);
b2Vec2 cLocal = b2MulT(xfA, c);
// Find the min separating edge.
int32 normalIndex = 0;
float separation = -b2_maxFloat;
float radius = polygonA->m_radius + circleB->m_radius;
int32 vertexCount = polygonA->m_count;
const b2Vec2* vertices = polygonA->m_vertices;
const b2Vec2* normals = polygonA->m_normals;
for (int32 i = 0; i < vertexCount; ++i)
{
float s = b2Dot(normals[i], cLocal - vertices[i]);
if (s > radius)
{
// Early out.
return;
}
if (s > separation)
{
separation = s;
normalIndex = i;
}
}
// Vertices that subtend the incident face.
int32 vertIndex1 = normalIndex;
int32 vertIndex2 = vertIndex1 + 1 < vertexCount ? vertIndex1 + 1 : 0;
b2Vec2 v1 = vertices[vertIndex1];
b2Vec2 v2 = vertices[vertIndex2];
// If the center is inside the polygon ...
if (separation < b2_epsilon)
{
manifold->pointCount = 1;
manifold->type = b2Manifold::e_faceA;
manifold->localNormal = normals[normalIndex];
manifold->localPoint = 0.5f * (v1 + v2);
manifold->points[0].localPoint = circleB->m_p;
manifold->points[0].id.key = 0;
return;
}
// Compute barycentric coordinates
float u1 = b2Dot(cLocal - v1, v2 - v1);
float u2 = b2Dot(cLocal - v2, v1 - v2);
if (u1 <= 0.0f)
{
if (b2DistanceSquared(cLocal, v1) > radius * radius)
{
return;
}
manifold->pointCount = 1;
manifold->type = b2Manifold::e_faceA;
manifold->localNormal = cLocal - v1;
manifold->localNormal.Normalize();
manifold->localPoint = v1;
manifold->points[0].localPoint = circleB->m_p;
manifold->points[0].id.key = 0;
}
else if (u2 <= 0.0f)
{
if (b2DistanceSquared(cLocal, v2) > radius * radius)
{
return;
}
manifold->pointCount = 1;
manifold->type = b2Manifold::e_faceA;
manifold->localNormal = cLocal - v2;
manifold->localNormal.Normalize();
manifold->localPoint = v2;
manifold->points[0].localPoint = circleB->m_p;
manifold->points[0].id.key = 0;
}
else
{
b2Vec2 faceCenter = 0.5f * (v1 + v2);
float s = b2Dot(cLocal - faceCenter, normals[vertIndex1]);
if (s > radius)
{
return;
}
manifold->pointCount = 1;
manifold->type = b2Manifold::e_faceA;
manifold->localNormal = normals[vertIndex1];
manifold->localPoint = faceCenter;
manifold->points[0].localPoint = circleB->m_p;
manifold->points[0].id.key = 0;
}
}
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