shape_cast.cpp

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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 "test.h"
#include "box2d/b2_distance.h"

class ShapeCast : public Test
{
public:
        enum
        {
                e_vertexCount = 8
        };

        ShapeCast()
        {
#if 1
                m_vAs[0].Set(-0.5f, 1.0f);
                m_vAs[1].Set(0.5f, 1.0f);
                m_vAs[2].Set(0.0f, 0.0f);
                m_countA = 3;
                m_radiusA = b2_polygonRadius;

                m_vBs[0].Set(-0.5f, -0.5f);
                m_vBs[1].Set(0.5f, -0.5f);
                m_vBs[2].Set(0.5f, 0.5f);
                m_vBs[3].Set(-0.5f, 0.5f);
                m_countB = 4;
                m_radiusB = b2_polygonRadius;

                m_transformA.p.Set(0.0f, 0.25f);
                m_transformA.q.SetIdentity();
                m_transformB.p.Set(-4.0f, 0.0f);
                m_transformB.q.SetIdentity();
                m_translationB.Set(8.0f, 0.0f);
#elif 0
                m_vAs[0].Set(0.0f, 0.0f);
                m_countA = 1;
                m_radiusA = 0.5f;

                m_vBs[0].Set(0.0f, 0.0f);
                m_countB = 1;
                m_radiusB = 0.5f;

                m_transformA.p.Set(0.0f, 0.25f);
                m_transformA.q.SetIdentity();
                m_transformB.p.Set(-4.0f, 0.0f);
                m_transformB.q.SetIdentity();
                m_translationB.Set(8.0f, 0.0f);
#else
                m_vAs[0].Set(0.0f, 0.0f);
                m_vAs[1].Set(2.0f, 0.0f);
                m_countA = 2;
                m_radiusA = b2_polygonRadius;

                m_vBs[0].Set(0.0f, 0.0f);
                m_countB = 1;
                m_radiusB = 0.25f;

                // Initial overlap
                m_transformA.p.Set(0.0f, 0.0f);
                m_transformA.q.SetIdentity();
                m_transformB.p.Set(-0.244360745f, 0.05999358f);
                m_transformB.q.SetIdentity();
                m_translationB.Set(0.0f, 0.0399999991f);
#endif
        }

        static Test* Create()
        {
                return new ShapeCast;
        }

        void Step(Settings& settings) override
        {
                Test::Step(settings);

                b2ShapeCastInput input;
                input.proxyA.Set(m_vAs, m_countA, m_radiusA);
                input.proxyB.Set(m_vBs, m_countB, m_radiusB);
                input.transformA = m_transformA;
                input.transformB = m_transformB;
                input.translationB = m_translationB;

                b2ShapeCastOutput output;
                bool hit = b2ShapeCast(&output, &input);

                b2Transform transformB2;
                transformB2.q = m_transformB.q;
                transformB2.p = m_transformB.p + output.lambda * input.translationB;

                b2DistanceInput distanceInput;
                distanceInput.proxyA.Set(m_vAs, m_countA, m_radiusA);
                distanceInput.proxyB.Set(m_vBs, m_countB, m_radiusB);
                distanceInput.transformA = m_transformA;
                distanceInput.transformB = transformB2;
                distanceInput.useRadii = false;
                b2SimplexCache simplexCache;
                simplexCache.count = 0;
                b2DistanceOutput distanceOutput;

                b2Distance(&distanceOutput, &simplexCache, &distanceInput);

                g_debugDraw.DrawString(5, m_textLine, "hit = %s, iters = %d, lambda = %g, distance = %g",
                        hit ? "true" : "false", output.iterations, output.lambda, distanceOutput.distance);
                m_textLine += m_textIncrement;

                b2Vec2 vertices[b2_maxPolygonVertices];

                for (int32 i = 0; i < m_countA; ++i)
                {
                        vertices[i] = b2Mul(m_transformA, m_vAs[i]);
                }

                if (m_countA == 1)
                {
                        g_debugDraw.DrawCircle(vertices[0], m_radiusA, b2Color(0.9f, 0.9f, 0.9f));
                }
                else
                {
                        g_debugDraw.DrawPolygon(vertices, m_countA, b2Color(0.9f, 0.9f, 0.9f));
                }

                for (int32 i = 0; i < m_countB; ++i)
                {
                        vertices[i] = b2Mul(m_transformB, m_vBs[i]);
                }

                if (m_countB == 1)
                {
                        g_debugDraw.DrawCircle(vertices[0], m_radiusB, b2Color(0.5f, 0.9f, 0.5f));
                }
                else
                {
                        g_debugDraw.DrawPolygon(vertices, m_countB, b2Color(0.5f, 0.9f, 0.5f));
                }

                for (int32 i = 0; i < m_countB; ++i)
                {
                        vertices[i] = b2Mul(transformB2, m_vBs[i]);
                }

                if (m_countB == 1)
                {
                        g_debugDraw.DrawCircle(vertices[0], m_radiusB, b2Color(0.5f, 0.7f, 0.9f));
                }
                else
                {
                        g_debugDraw.DrawPolygon(vertices, m_countB, b2Color(0.5f, 0.7f, 0.9f));
                }

                if (hit)
                {
                        b2Vec2 p1 = output.point;
                        g_debugDraw.DrawPoint(p1, 10.0f, b2Color(0.9f, 0.3f, 0.3f));
                        b2Vec2 p2 = p1 + output.normal;
                        g_debugDraw.DrawSegment(p1, p2, b2Color(0.9f, 0.3f, 0.3f));
                }
        }

        b2Vec2 m_vAs[b2_maxPolygonVertices];
        int32 m_countA;
        float m_radiusA;

        b2Vec2 m_vBs[b2_maxPolygonVertices];
        int32 m_countB;
        float m_radiusB;

        b2Transform m_transformA;
        b2Transform m_transformB;
        b2Vec2 m_translationB;
};

static int testIndex = RegisterTest("Collision", "Shape Cast", ShapeCast::Create);