253 lines
6.3 KiB
C++
253 lines
6.3 KiB
C++
/*
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* Copyright (c) 2007-2009 Erin Catto http://www.box2d.org
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#include "Box2D/Collision/b2Collision.h"
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#include "Box2D/Collision/b2Distance.h"
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void b2WorldManifold::Initialize(const b2Manifold* manifold,
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const b2Transform& xfA, float32 radiusA,
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const b2Transform& xfB, float32 radiusB)
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{
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if (manifold->pointCount == 0)
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{
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return;
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}
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switch (manifold->type)
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{
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case b2Manifold::e_circles:
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{
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normal.Set(1.0f, 0.0f);
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b2Vec2 pointA = b2Mul(xfA, manifold->localPoint);
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b2Vec2 pointB = b2Mul(xfB, manifold->points[0].localPoint);
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if (b2DistanceSquared(pointA, pointB) > b2_epsilon * b2_epsilon)
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{
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normal = pointB - pointA;
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normal.Normalize();
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}
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b2Vec2 cA = pointA + radiusA * normal;
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b2Vec2 cB = pointB - radiusB * normal;
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points[0] = 0.5f * (cA + cB);
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separations[0] = b2Dot(cB - cA, normal);
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}
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break;
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case b2Manifold::e_faceA:
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{
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normal = b2Mul(xfA.q, manifold->localNormal);
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b2Vec2 planePoint = b2Mul(xfA, manifold->localPoint);
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for (int32 i = 0; i < manifold->pointCount; ++i)
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{
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b2Vec2 clipPoint = b2Mul(xfB, manifold->points[i].localPoint);
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b2Vec2 cA = clipPoint + (radiusA - b2Dot(clipPoint - planePoint, normal)) * normal;
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b2Vec2 cB = clipPoint - radiusB * normal;
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points[i] = 0.5f * (cA + cB);
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separations[i] = b2Dot(cB - cA, normal);
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}
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}
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break;
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case b2Manifold::e_faceB:
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{
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normal = b2Mul(xfB.q, manifold->localNormal);
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b2Vec2 planePoint = b2Mul(xfB, manifold->localPoint);
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for (int32 i = 0; i < manifold->pointCount; ++i)
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{
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b2Vec2 clipPoint = b2Mul(xfA, manifold->points[i].localPoint);
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b2Vec2 cB = clipPoint + (radiusB - b2Dot(clipPoint - planePoint, normal)) * normal;
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b2Vec2 cA = clipPoint - radiusA * normal;
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points[i] = 0.5f * (cA + cB);
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separations[i] = b2Dot(cA - cB, normal);
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}
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// Ensure normal points from A to B.
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normal = -normal;
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}
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break;
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}
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}
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void b2GetPointStates(b2PointState state1[b2_maxManifoldPoints], b2PointState state2[b2_maxManifoldPoints],
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const b2Manifold* manifold1, const b2Manifold* manifold2)
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{
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for (int32 i = 0; i < b2_maxManifoldPoints; ++i)
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{
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state1[i] = b2_nullState;
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state2[i] = b2_nullState;
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}
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// Detect persists and removes.
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for (int32 i = 0; i < manifold1->pointCount; ++i)
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{
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b2ContactID id = manifold1->points[i].id;
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state1[i] = b2_removeState;
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for (int32 j = 0; j < manifold2->pointCount; ++j)
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{
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if (manifold2->points[j].id.key == id.key)
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{
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state1[i] = b2_persistState;
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break;
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}
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}
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}
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// Detect persists and adds.
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for (int32 i = 0; i < manifold2->pointCount; ++i)
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{
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b2ContactID id = manifold2->points[i].id;
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state2[i] = b2_addState;
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for (int32 j = 0; j < manifold1->pointCount; ++j)
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{
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if (manifold1->points[j].id.key == id.key)
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{
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state2[i] = b2_persistState;
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break;
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}
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}
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}
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}
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// From Real-time Collision Detection, p179.
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bool b2AABB::RayCast(b2RayCastOutput* output, const b2RayCastInput& input) const
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{
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float32 tmin = -b2_maxFloat;
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float32 tmax = b2_maxFloat;
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b2Vec2 p = input.p1;
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b2Vec2 d = input.p2 - input.p1;
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b2Vec2 absD = b2Abs(d);
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b2Vec2 normal;
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for (int32 i = 0; i < 2; ++i)
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{
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if (absD(i) < b2_epsilon)
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{
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// Parallel.
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if (p(i) < lowerBound(i) || upperBound(i) < p(i))
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{
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return false;
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}
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}
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else
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{
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float32 inv_d = 1.0f / d(i);
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float32 t1 = (lowerBound(i) - p(i)) * inv_d;
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float32 t2 = (upperBound(i) - p(i)) * inv_d;
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// Sign of the normal vector.
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float32 s = -1.0f;
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if (t1 > t2)
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{
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b2Swap(t1, t2);
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s = 1.0f;
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}
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// Push the min up
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if (t1 > tmin)
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{
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normal.SetZero();
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normal(i) = s;
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tmin = t1;
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}
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// Pull the max down
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tmax = b2Min(tmax, t2);
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if (tmin > tmax)
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{
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return false;
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}
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}
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}
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// Does the ray start inside the box?
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// Does the ray intersect beyond the max fraction?
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if (tmin < 0.0f || input.maxFraction < tmin)
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{
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return false;
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}
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// Intersection.
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output->fraction = tmin;
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output->normal = normal;
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return true;
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}
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// Sutherland-Hodgman clipping.
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int32 b2ClipSegmentToLine(b2ClipVertex vOut[2], const b2ClipVertex vIn[2],
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const b2Vec2& normal, float32 offset, int32 vertexIndexA)
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{
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// Start with no output points
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int32 numOut = 0;
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// Calculate the distance of end points to the line
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float32 distance0 = b2Dot(normal, vIn[0].v) - offset;
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float32 distance1 = b2Dot(normal, vIn[1].v) - offset;
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// If the points are behind the plane
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if (distance0 <= 0.0f) vOut[numOut++] = vIn[0];
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if (distance1 <= 0.0f) vOut[numOut++] = vIn[1];
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// If the points are on different sides of the plane
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if (distance0 * distance1 < 0.0f)
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{
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// Find intersection point of edge and plane
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float32 interp = distance0 / (distance0 - distance1);
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vOut[numOut].v = vIn[0].v + interp * (vIn[1].v - vIn[0].v);
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// VertexA is hitting edgeB.
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vOut[numOut].id.cf.indexA = static_cast<uint8>(vertexIndexA);
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vOut[numOut].id.cf.indexB = vIn[0].id.cf.indexB;
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vOut[numOut].id.cf.typeA = b2ContactFeature::e_vertex;
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vOut[numOut].id.cf.typeB = b2ContactFeature::e_face;
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++numOut;
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}
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return numOut;
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}
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bool b2TestOverlap( const b2Shape* shapeA, int32 indexA,
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const b2Shape* shapeB, int32 indexB,
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const b2Transform& xfA, const b2Transform& xfB)
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{
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b2DistanceInput input;
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input.proxyA.Set(shapeA, indexA);
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input.proxyB.Set(shapeB, indexB);
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input.transformA = xfA;
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input.transformB = xfB;
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input.useRadii = true;
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b2SimplexCache cache;
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cache.count = 0;
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b2DistanceOutput output;
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b2Distance(&output, &cache, &input);
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return output.distance < 10.0f * b2_epsilon;
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}
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