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Diffstat (limited to 'ThirdParty/Box2D/Collision/b2TimeOfImpact.cpp')
| -rw-r--r-- | ThirdParty/Box2D/Collision/b2TimeOfImpact.cpp | 486 |
1 files changed, 486 insertions, 0 deletions
diff --git a/ThirdParty/Box2D/Collision/b2TimeOfImpact.cpp b/ThirdParty/Box2D/Collision/b2TimeOfImpact.cpp new file mode 100644 index 0000000..4bc1769 --- /dev/null +++ b/ThirdParty/Box2D/Collision/b2TimeOfImpact.cpp @@ -0,0 +1,486 @@ +/* +* Copyright (c) 2007-2009 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/b2Distance.h" +#include "Box2D/Collision/b2TimeOfImpact.h" +#include "Box2D/Collision/Shapes/b2CircleShape.h" +#include "Box2D/Collision/Shapes/b2PolygonShape.h" +#include "Box2D/Common/b2Timer.h" + +#include <stdio.h> + +float32 b2_toiTime, b2_toiMaxTime; +int32 b2_toiCalls, b2_toiIters, b2_toiMaxIters; +int32 b2_toiRootIters, b2_toiMaxRootIters; + +// +struct b2SeparationFunction +{ + enum Type + { + e_points, + e_faceA, + e_faceB + }; + + // TODO_ERIN might not need to return the separation + + float32 Initialize(const b2SimplexCache* cache, + const b2DistanceProxy* proxyA, const b2Sweep& sweepA, + const b2DistanceProxy* proxyB, const b2Sweep& sweepB, + float32 t1) + { + m_proxyA = proxyA; + m_proxyB = proxyB; + int32 count = cache->count; + b2Assert(0 < count && count < 3); + + m_sweepA = sweepA; + m_sweepB = sweepB; + + b2Transform xfA, xfB; + m_sweepA.GetTransform(&xfA, t1); + m_sweepB.GetTransform(&xfB, t1); + + if (count == 1) + { + m_type = e_points; + b2Vec2 localPointA = m_proxyA->GetVertex(cache->indexA[0]); + b2Vec2 localPointB = m_proxyB->GetVertex(cache->indexB[0]); + b2Vec2 pointA = b2Mul(xfA, localPointA); + b2Vec2 pointB = b2Mul(xfB, localPointB); + m_axis = pointB - pointA; + float32 s = m_axis.Normalize(); + return s; + } + else if (cache->indexA[0] == cache->indexA[1]) + { + // Two points on B and one on A. + m_type = e_faceB; + b2Vec2 localPointB1 = proxyB->GetVertex(cache->indexB[0]); + b2Vec2 localPointB2 = proxyB->GetVertex(cache->indexB[1]); + + m_axis = b2Cross(localPointB2 - localPointB1, 1.0f); + m_axis.Normalize(); + b2Vec2 normal = b2Mul(xfB.q, m_axis); + + m_localPoint = 0.5f * (localPointB1 + localPointB2); + b2Vec2 pointB = b2Mul(xfB, m_localPoint); + + b2Vec2 localPointA = proxyA->GetVertex(cache->indexA[0]); + b2Vec2 pointA = b2Mul(xfA, localPointA); + + float32 s = b2Dot(pointA - pointB, normal); + if (s < 0.0f) + { + m_axis = -m_axis; + s = -s; + } + return s; + } + else + { + // Two points on A and one or two points on B. + m_type = e_faceA; + b2Vec2 localPointA1 = m_proxyA->GetVertex(cache->indexA[0]); + b2Vec2 localPointA2 = m_proxyA->GetVertex(cache->indexA[1]); + + m_axis = b2Cross(localPointA2 - localPointA1, 1.0f); + m_axis.Normalize(); + b2Vec2 normal = b2Mul(xfA.q, m_axis); + + m_localPoint = 0.5f * (localPointA1 + localPointA2); + b2Vec2 pointA = b2Mul(xfA, m_localPoint); + + b2Vec2 localPointB = m_proxyB->GetVertex(cache->indexB[0]); + b2Vec2 pointB = b2Mul(xfB, localPointB); + + float32 s = b2Dot(pointB - pointA, normal); + if (s < 0.0f) + { + m_axis = -m_axis; + s = -s; + } + return s; + } + } + + // + float32 FindMinSeparation(int32* indexA, int32* indexB, float32 t) const + { + b2Transform xfA, xfB; + m_sweepA.GetTransform(&xfA, t); + m_sweepB.GetTransform(&xfB, t); + + switch (m_type) + { + case e_points: + { + b2Vec2 axisA = b2MulT(xfA.q, m_axis); + b2Vec2 axisB = b2MulT(xfB.q, -m_axis); + + *indexA = m_proxyA->GetSupport(axisA); + *indexB = m_proxyB->GetSupport(axisB); + + b2Vec2 localPointA = m_proxyA->GetVertex(*indexA); + b2Vec2 localPointB = m_proxyB->GetVertex(*indexB); + + b2Vec2 pointA = b2Mul(xfA, localPointA); + b2Vec2 pointB = b2Mul(xfB, localPointB); + + float32 separation = b2Dot(pointB - pointA, m_axis); + return separation; + } + + case e_faceA: + { + b2Vec2 normal = b2Mul(xfA.q, m_axis); + b2Vec2 pointA = b2Mul(xfA, m_localPoint); + + b2Vec2 axisB = b2MulT(xfB.q, -normal); + + *indexA = -1; + *indexB = m_proxyB->GetSupport(axisB); + + b2Vec2 localPointB = m_proxyB->GetVertex(*indexB); + b2Vec2 pointB = b2Mul(xfB, localPointB); + + float32 separation = b2Dot(pointB - pointA, normal); + return separation; + } + + case e_faceB: + { + b2Vec2 normal = b2Mul(xfB.q, m_axis); + b2Vec2 pointB = b2Mul(xfB, m_localPoint); + + b2Vec2 axisA = b2MulT(xfA.q, -normal); + + *indexB = -1; + *indexA = m_proxyA->GetSupport(axisA); + + b2Vec2 localPointA = m_proxyA->GetVertex(*indexA); + b2Vec2 pointA = b2Mul(xfA, localPointA); + + float32 separation = b2Dot(pointA - pointB, normal); + return separation; + } + + default: + b2Assert(false); + *indexA = -1; + *indexB = -1; + return 0.0f; + } + } + + // + float32 Evaluate(int32 indexA, int32 indexB, float32 t) const + { + b2Transform xfA, xfB; + m_sweepA.GetTransform(&xfA, t); + m_sweepB.GetTransform(&xfB, t); + + switch (m_type) + { + case e_points: + { + b2Vec2 localPointA = m_proxyA->GetVertex(indexA); + b2Vec2 localPointB = m_proxyB->GetVertex(indexB); + + b2Vec2 pointA = b2Mul(xfA, localPointA); + b2Vec2 pointB = b2Mul(xfB, localPointB); + float32 separation = b2Dot(pointB - pointA, m_axis); + + return separation; + } + + case e_faceA: + { + b2Vec2 normal = b2Mul(xfA.q, m_axis); + b2Vec2 pointA = b2Mul(xfA, m_localPoint); + + b2Vec2 localPointB = m_proxyB->GetVertex(indexB); + b2Vec2 pointB = b2Mul(xfB, localPointB); + + float32 separation = b2Dot(pointB - pointA, normal); + return separation; + } + + case e_faceB: + { + b2Vec2 normal = b2Mul(xfB.q, m_axis); + b2Vec2 pointB = b2Mul(xfB, m_localPoint); + + b2Vec2 localPointA = m_proxyA->GetVertex(indexA); + b2Vec2 pointA = b2Mul(xfA, localPointA); + + float32 separation = b2Dot(pointA - pointB, normal); + return separation; + } + + default: + b2Assert(false); + return 0.0f; + } + } + + const b2DistanceProxy* m_proxyA; + const b2DistanceProxy* m_proxyB; + b2Sweep m_sweepA, m_sweepB; + Type m_type; + b2Vec2 m_localPoint; + b2Vec2 m_axis; +}; + +// CCD via the local separating axis method. This seeks progression +// by computing the largest time at which separation is maintained. +void b2TimeOfImpact(b2TOIOutput* output, const b2TOIInput* input) +{ + b2Timer timer; + + ++b2_toiCalls; + + output->state = b2TOIOutput::e_unknown; + output->t = input->tMax; + + const b2DistanceProxy* proxyA = &input->proxyA; + const b2DistanceProxy* proxyB = &input->proxyB; + + b2Sweep sweepA = input->sweepA; + b2Sweep sweepB = input->sweepB; + + // Large rotations can make the root finder fail, so we normalize the + // sweep angles. + sweepA.Normalize(); + sweepB.Normalize(); + + float32 tMax = input->tMax; + + float32 totalRadius = proxyA->m_radius + proxyB->m_radius; + float32 target = b2Max(b2_linearSlop, totalRadius - 3.0f * b2_linearSlop); + float32 tolerance = 0.25f * b2_linearSlop; + b2Assert(target > tolerance); + + float32 t1 = 0.0f; + const int32 k_maxIterations = 20; // TODO_ERIN b2Settings + int32 iter = 0; + + // Prepare input for distance query. + b2SimplexCache cache; + cache.count = 0; + b2DistanceInput distanceInput; + distanceInput.proxyA = input->proxyA; + distanceInput.proxyB = input->proxyB; + distanceInput.useRadii = false; + + // The outer loop progressively attempts to compute new separating axes. + // This loop terminates when an axis is repeated (no progress is made). + for(;;) + { + b2Transform xfA, xfB; + sweepA.GetTransform(&xfA, t1); + sweepB.GetTransform(&xfB, t1); + + // Get the distance between shapes. We can also use the results + // to get a separating axis. + distanceInput.transformA = xfA; + distanceInput.transformB = xfB; + b2DistanceOutput distanceOutput; + b2Distance(&distanceOutput, &cache, &distanceInput); + + // If the shapes are overlapped, we give up on continuous collision. + if (distanceOutput.distance <= 0.0f) + { + // Failure! + output->state = b2TOIOutput::e_overlapped; + output->t = 0.0f; + break; + } + + if (distanceOutput.distance < target + tolerance) + { + // Victory! + output->state = b2TOIOutput::e_touching; + output->t = t1; + break; + } + + // Initialize the separating axis. + b2SeparationFunction fcn; + fcn.Initialize(&cache, proxyA, sweepA, proxyB, sweepB, t1); +#if 0 + // Dump the curve seen by the root finder + { + const int32 N = 100; + float32 dx = 1.0f / N; + float32 xs[N+1]; + float32 fs[N+1]; + + float32 x = 0.0f; + + for (int32 i = 0; i <= N; ++i) + { + sweepA.GetTransform(&xfA, x); + sweepB.GetTransform(&xfB, x); + float32 f = fcn.Evaluate(xfA, xfB) - target; + + printf("%g %g\n", x, f); + + xs[i] = x; + fs[i] = f; + + x += dx; + } + } +#endif + + // Compute the TOI on the separating axis. We do this by successively + // resolving the deepest point. This loop is bounded by the number of vertices. + bool done = false; + float32 t2 = tMax; + int32 pushBackIter = 0; + for (;;) + { + // Find the deepest point at t2. Store the witness point indices. + int32 indexA, indexB; + float32 s2 = fcn.FindMinSeparation(&indexA, &indexB, t2); + + // Is the final configuration separated? + if (s2 > target + tolerance) + { + // Victory! + output->state = b2TOIOutput::e_separated; + output->t = tMax; + done = true; + break; + } + + // Has the separation reached tolerance? + if (s2 > target - tolerance) + { + // Advance the sweeps + t1 = t2; + break; + } + + // Compute the initial separation of the witness points. + float32 s1 = fcn.Evaluate(indexA, indexB, t1); + + // Check for initial overlap. This might happen if the root finder + // runs out of iterations. + if (s1 < target - tolerance) + { + output->state = b2TOIOutput::e_failed; + output->t = t1; + done = true; + break; + } + + // Check for touching + if (s1 <= target + tolerance) + { + // Victory! t1 should hold the TOI (could be 0.0). + output->state = b2TOIOutput::e_touching; + output->t = t1; + done = true; + break; + } + + // Compute 1D root of: f(x) - target = 0 + int32 rootIterCount = 0; + float32 a1 = t1, a2 = t2; + for (;;) + { + // Use a mix of the secant rule and bisection. + float32 t; + if (rootIterCount & 1) + { + // Secant rule to improve convergence. + t = a1 + (target - s1) * (a2 - a1) / (s2 - s1); + } + else + { + // Bisection to guarantee progress. + t = 0.5f * (a1 + a2); + } + + ++rootIterCount; + ++b2_toiRootIters; + + float32 s = fcn.Evaluate(indexA, indexB, t); + + if (b2Abs(s - target) < tolerance) + { + // t2 holds a tentative value for t1 + t2 = t; + break; + } + + // Ensure we continue to bracket the root. + if (s > target) + { + a1 = t; + s1 = s; + } + else + { + a2 = t; + s2 = s; + } + + if (rootIterCount == 50) + { + break; + } + } + + b2_toiMaxRootIters = b2Max(b2_toiMaxRootIters, rootIterCount); + + ++pushBackIter; + + if (pushBackIter == b2_maxPolygonVertices) + { + break; + } + } + + ++iter; + ++b2_toiIters; + + if (done) + { + break; + } + + if (iter == k_maxIterations) + { + // Root finder got stuck. Semi-victory. + output->state = b2TOIOutput::e_failed; + output->t = t1; + break; + } + } + + b2_toiMaxIters = b2Max(b2_toiMaxIters, iter); + + float32 time = timer.GetMilliseconds(); + b2_toiMaxTime = b2Max(b2_toiMaxTime, time); + b2_toiTime += time; +} |