Box2DX.Collision.Simplex.GetWitnessPoints C# (CSharp) Метод

		internal unsafe void GetWitnessPoints(Vector2* pA, Vector2* pB)
		{
			switch (_count)
			{
				case 0:
					Box2DXDebug.Assert(false);
					break;

				case 1:
					*pA = _v1.wA;
					*pB = _v1.wB;
					break;

				case 2:
					*pA = _v1.a * _v1.wA + _v2.a * _v2.wA;
					*pB = _v1.a * _v1.wB + _v2.a * _v2.wB;
					break;

				case 3:
					*pA = _v1.a * _v1.wA + _v2.a * _v2.wA + _v3.a * _v3.wA;
					*pB = *pA;
					break;

				default:
					Box2DXDebug.Assert(false);
					break;
			}
		}
#else

		static void Distance(out DistanceOutput output, ref SimplexCache cache, ref DistanceInput input, Shape shapeA, Shape shapeB)
		{
			output = new DistanceOutput();

			Transform transformA = input.TransformA;
			Transform transformB = input.TransformB;

			// Initialize the simplex.
			Simplex simplex = new Simplex();
#if ALLOWUNSAFE
			fixed (SimplexCache* sPtr = &cache)
			{
				simplex.ReadCache(sPtr, shapeA, transformA, shapeB, transformB);
			}
#else
			simplex.ReadCache(cache, shapeA, transformA, shapeB, transformB);
#endif

			// Get simplex vertices as an array.
#if ALLOWUNSAFE
			SimplexVertex* vertices = &simplex._v1;
#else
			SimplexVertex[] vertices = new SimplexVertex[] { simplex._v1, simplex._v2, simplex._v3 };
#endif 

			// These store the vertices of the last simplex so that we
			// can check for duplicates and prevent cycling.
#if ALLOWUNSAFE
			int* lastA = stackalloc int[4], lastB = stackalloc int[4];
#else
			int[] lastA = new int[4];
			int[] lastB = new int[4];
#endif // ALLOWUNSAFE
			int lastCount;

			// Main iteration loop.
			int iter = 0;
			const int k_maxIterationCount = 20;
			while (iter < k_maxIterationCount)
			{
				// Copy simplex so we can identify duplicates.
				lastCount = simplex._count;
				int i;
				for (i = 0; i < lastCount; ++i)
				{
					lastA[i] = vertices[i].indexA;
					lastB[i] = vertices[i].indexB;
				}

				switch (simplex._count)
				{
					case 1:
						break;

					case 2:
						simplex.Solve2();
						break;

					case 3:
						simplex.Solve3();
						break;

					default:
#if DEBUG
						Box2DXDebug.Assert(false);
#endif
						break;
				}

				// If we have 3 points, then the origin is in the corresponding triangle.
				if (simplex._count == 3)
				{
					break;
				}

				// Compute closest point.
				Vector2 p = simplex.GetClosestPoint();
				float distanceSqr = p.sqrMagnitude;

				// Ensure the search direction is numerically fit.
				if (distanceSqr < Common.Settings.FLT_EPSILON_SQUARED)
				{
					// The origin is probably contained by a line segment
					// or triangle. Thus the shapes are overlapped.

					// We can't return zero here even though there may be overlap.
					// In case the simplex is a point, segment, or triangle it is difficult
					// to determine if the origin is contained in the CSO or very close to it.
					break;
				}

				// Compute a tentative new simplex vertex using support points.
#if ALLOWUNSAFE
				SimplexVertex* vertex = vertices + simplex._count;
				vertex->indexA = shapeA.GetSupport(transformA.InverseTransformDirection(p));
				vertex->wA = transformA.TransformPoint(shapeA.GetVertex(vertex->indexA));
				//Vec2 wBLocal;
				vertex->indexB = shapeB.GetSupport(transformB.InverseTransformDirection(-p));
				vertex->wB = transformB.TransformPoint(shapeB.GetVertex(vertex->indexB));
				vertex->w = vertex->wB - vertex->wA;
#else
				SimplexVertex vertex = vertices[simplex._count - 1];
				vertex.indexA = shapeA.GetSupport(transformA.InverseTransformDirection(p));
				vertex.wA = transformA.TransformPoint(shapeA.GetVertex(vertex.indexA));
				//Vec2 wBLocal;
				vertex.indexB = shapeB.GetSupport(transformB.InverseTransformDirection(-p));
				vertex.wB = transformB.TransformPoint(shapeB.GetVertex(vertex.indexB));
				vertex.w = vertex.wB - vertex.wA;	
#endif // ALLOWUNSAFE

				// Iteration count is equated to the number of support point calls.
				++iter;

				// Check for convergence.
#if ALLOWUNSAFE
				float lowerBound = Vector2.Dot(p, vertex->w);
#else
				float lowerBound = Vector2.Dot(p, vertex.w);
#endif
				float upperBound = distanceSqr;
				const float k_relativeTolSqr = 0.01f * 0.01f;	// 1:100
				if (upperBound - lowerBound <= k_relativeTolSqr * upperBound)
				{
					// Converged!
					break;
				}

				// Check for duplicate support points.
				bool duplicate = false;
				for (i = 0; i < lastCount; ++i)
				{
#if ALLOWUNSAFE
					if (vertex->indexA == lastA[i] && vertex->indexB == lastB[i])
#else
					if (vertex.indexA == lastA[i] && vertex.indexB == lastB[i])
#endif
					{
						duplicate = true;
						break;
					}
				}

				// If we found a duplicate support point we must exit to avoid cycling.
				if (duplicate)
				{
					break;
				}

				// New vertex is ok and needed.
				++simplex._count;
			}

			
#if ALLOWUNSAFE
			fixed (DistanceOutput* doPtr = &output)
			{
				// Prepare output.
				simplex.GetWitnessPoints(&doPtr->PointA, &doPtr->PointB);
				doPtr->Distance = Vector2.Distance(doPtr->PointA, doPtr->PointB);
				doPtr->Iterations = iter;
			}

			fixed (SimplexCache* sPtr = &cache)
			{
				// Cache the simplex.
				simplex.WriteCache(sPtr);
			}
#else
			// Prepare output.
			simplex.GetWitnessPoints(out output.PointA, out output.PointB);
			output.Distance = Vector2.Distance(output.PointA, output.PointB);
			output.Iterations = iter;
			
			// Cache the simplex.
			simplex.WriteCache(cache);
#endif

			// Apply radii if requested.
			if (input.UseRadii)
			{
				float rA = shapeA._radius;
				float rB = shapeB._radius;

				if (output.Distance > rA + rB && output.Distance > Common.Settings.FLT_EPSILON)
				{
					// Shapes are still no overlapped.
					// Move the witness points to the outer surface.
					output.Distance -= rA + rB;
					Vector2 normal = output.PointB - output.PointA;
					normal.Normalize();
					output.PointA += rA * normal;
					output.PointB -= rB * normal;
				}
				else
				{
					// Shapes are overlapped when radii are considered.
					// Move the witness points to the middle.
					Vector2 p = 0.5f * (output.PointA + output.PointB);
					output.PointA = p;
					output.PointB = p;
					output.Distance = 0.0f;
				}
			}
		}