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/*
* Copyright (c) 2007 Erin Catto http://www.gphysics.com
*
* 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/b2CircleShape.h"
#include "Shapes/b2PolygonShape.h"
void b2CollideCircles(
b2Manifold* manifold,
const b2CircleShape* circle1, const b2XForm& xf1,
const b2CircleShape* circle2, const b2XForm& xf2)
{
manifold->pointCount = 0;
b2Vec2 p1 = b2Mul(xf1, circle1->GetLocalPosition());
b2Vec2 p2 = b2Mul(xf2, circle2->GetLocalPosition());
b2Vec2 d = p2 - p1;
float32 distSqr = b2Dot(d, d);
float32 r1 = circle1->GetRadius();
float32 r2 = circle2->GetRadius();
float32 radiusSum = r1 + r2;
if (distSqr > radiusSum * radiusSum)
{
return;
}
float32 separation;
if (distSqr < B2_FLT_EPSILON)
{
separation = -radiusSum;
manifold->normal.Set(0.0f, 1.0f);
}
else
{
float32 dist = b2Sqrt(distSqr);
separation = dist - radiusSum;
float32 a = 1.0f / dist;
manifold->normal.x = a * d.x;
manifold->normal.y = a * d.y;
}
manifold->pointCount = 1;
manifold->points[0].id.key = 0;
manifold->points[0].separation = separation;
p1 += r1 * manifold->normal;
p2 -= r2 * manifold->normal;
b2Vec2 p = 0.5f * (p1 + p2);
manifold->points[0].localPoint1 = b2MulT(xf1, p);
manifold->points[0].localPoint2 = b2MulT(xf2, p);
}
void b2CollidePolygonAndCircle(
b2Manifold* manifold,
const b2PolygonShape* polygon, const b2XForm& xf1,
const b2CircleShape* circle, const b2XForm& xf2)
{
manifold->pointCount = 0;
// Compute circle position in the frame of the polygon.
b2Vec2 c = b2Mul(xf2, circle->GetLocalPosition());
b2Vec2 cLocal = b2MulT(xf1, c);
// Find the min separating edge.
int32 normalIndex = 0;
float32 separation = -B2_FLT_MAX;
float32 radius = circle->GetRadius();
int32 vertexCount = polygon->GetVertexCount();
const b2Vec2* vertices = polygon->GetVertices();
const b2Vec2* normals = polygon->GetNormals();
for (int32 i = 0; i < vertexCount; ++i)
{
float32 s = b2Dot(normals[i], cLocal - vertices[i]);
if (s > radius)
{
// Early out.
return;
}
if (s > separation)
{
separation = s;
normalIndex = i;
}
}
// If the center is inside the polygon ...
if (separation < B2_FLT_EPSILON)
{
manifold->pointCount = 1;
manifold->normal = b2Mul(xf1.R, normals[normalIndex]);
manifold->points[0].id.features.incidentEdge = (uint8)normalIndex;
manifold->points[0].id.features.incidentVertex = b2_nullFeature;
manifold->points[0].id.features.referenceEdge = 0;
manifold->points[0].id.features.flip = 0;
b2Vec2 position = c - radius * manifold->normal;
manifold->points[0].localPoint1 = b2MulT(xf1, position);
manifold->points[0].localPoint2 = b2MulT(xf2, position);
manifold->points[0].separation = separation - radius;
return;
}
// Project the circle center onto the edge segment.
int32 vertIndex1 = normalIndex;
int32 vertIndex2 = vertIndex1 + 1 < vertexCount ? vertIndex1 + 1 : 0;
b2Vec2 e = vertices[vertIndex2] - vertices[vertIndex1];
float32 length = e.Normalize();
b2Assert(length > B2_FLT_EPSILON);
// Project the center onto the edge.
float32 u = b2Dot(cLocal - vertices[vertIndex1], e);
b2Vec2 p;
if (u <= 0.0f)
{
p = vertices[vertIndex1];
manifold->points[0].id.features.incidentEdge = b2_nullFeature;
manifold->points[0].id.features.incidentVertex = (uint8)vertIndex1;
}
else if (u >= length)
{
p = vertices[vertIndex2];
manifold->points[0].id.features.incidentEdge = b2_nullFeature;
manifold->points[0].id.features.incidentVertex = (uint8)vertIndex2;
}
else
{
p = vertices[vertIndex1] + u * e;
manifold->points[0].id.features.incidentEdge = (uint8)normalIndex;
manifold->points[0].id.features.incidentVertex = b2_nullFeature;
}
b2Vec2 d = cLocal - p;
float32 dist = d.Normalize();
if (dist > radius)
{
return;
}
manifold->pointCount = 1;
manifold->normal = b2Mul(xf1.R, d);
b2Vec2 position = c - radius * manifold->normal;
manifold->points[0].localPoint1 = b2MulT(xf1, position);
manifold->points[0].localPoint2 = b2MulT(xf2, position);
manifold->points[0].separation = dist - radius;
manifold->points[0].id.features.referenceEdge = 0;
manifold->points[0].id.features.flip = 0;
}
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