ray_cast.cpp

Go to the documentation of this file.

// 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 "settings.h"
#include "test.h"
#include "imgui/imgui.h"

enum
{
        e_maxBodies = 256
};

// This test demonstrates how to use the world ray-cast feature.
// NOTE: we are intentionally filtering one of the polygons, therefore
// the ray will always miss one type of polygon.

// This callback finds the closest hit. Polygon 0 is filtered.
class RayCastClosestCallback : public b2RayCastCallback
{
public:
        RayCastClosestCallback()
        {
                m_hit = false;
        }

        float ReportFixture(b2Fixture* fixture, const b2Vec2& point, const b2Vec2& normal, float fraction) override
        {
                uintptr_t index = fixture->GetUserData().pointer;
                if (index == 1)
                {
                        // By returning -1, we instruct the calling code to ignore this fixture and
                        // continue the ray-cast to the next fixture.
                        return -1.0f;
                }

                m_hit = true;
                m_point = point;
                m_normal = normal;

                // By returning the current fraction, we instruct the calling code to clip the ray and
                // continue the ray-cast to the next fixture. WARNING: do not assume that fixtures
                // are reported in order. However, by clipping, we can always get the closest fixture.
                return fraction;
        }
        
        bool m_hit;
        b2Vec2 m_point;
        b2Vec2 m_normal;
};

// This callback finds any hit. Polygon 0 is filtered. For this type of query we are usually
// just checking for obstruction, so the actual fixture and hit point are irrelevant. 
class RayCastAnyCallback : public b2RayCastCallback
{
public:
        RayCastAnyCallback()
        {
                m_hit = false;
        }

        float ReportFixture(b2Fixture* fixture, const b2Vec2& point, const b2Vec2& normal, float) override
        {
                uintptr_t index = fixture->GetUserData().pointer;
                if (index == 1)
                {
                        // By returning -1, we instruct the calling code to ignore this fixture and
                        // continue the ray-cast to the next fixture.
                        return -1.0f;
                }

                m_hit = true;
                m_point = point;
                m_normal = normal;

                // At this point we have a hit, so we know the ray is obstructed.
                // By returning 0, we instruct the calling code to terminate the ray-cast.
                return 0.0f;
        }

        bool m_hit;
        b2Vec2 m_point;
        b2Vec2 m_normal;
};

// This ray cast collects multiple hits along the ray. Polygon 0 is filtered.
// The fixtures are not necessary reported in order, so we might not capture
// the closest fixture.
class RayCastMultipleCallback : public b2RayCastCallback
{
public:
        enum
        {
                e_maxCount = 3
        };

        RayCastMultipleCallback()
        {
                m_count = 0;
        }

        float ReportFixture(b2Fixture* fixture, const b2Vec2& point, const b2Vec2& normal, float) override
        {
                uintptr_t index = fixture->GetUserData().pointer;
                if (index == 1)
                {
                        // By returning -1, we instruct the calling code to ignore this fixture and
                        // continue the ray-cast to the next fixture.
                        return -1.0f;
                }

                b2Assert(m_count < e_maxCount);

                m_points[m_count] = point;
                m_normals[m_count] = normal;
                ++m_count;

                if (m_count == e_maxCount)
                {
                        // At this point the buffer is full.
                        // By returning 0, we instruct the calling code to terminate the ray-cast.
                        return 0.0f;
                }

                // By returning 1, we instruct the caller to continue without clipping the ray.
                return 1.0f;
        }

        b2Vec2 m_points[e_maxCount];
        b2Vec2 m_normals[e_maxCount];
        int32 m_count;
};


class RayCast : public Test
{
public:

        enum Mode
        {
                e_any = 0,
                e_closest = 1,
                e_multiple = 2
        };

        RayCast()
        {
                // Ground body
                {
                        b2BodyDef bd;
                        b2Body* ground = m_world->CreateBody(&bd);

                        b2EdgeShape shape;
                        shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
                        ground->CreateFixture(&shape, 0.0f);
                }

                {
                        b2Vec2 vertices[3];
                        vertices[0].Set(-0.5f, 0.0f);
                        vertices[1].Set(0.5f, 0.0f);
                        vertices[2].Set(0.0f, 1.5f);
                        m_polygons[0].Set(vertices, 3);
                }

                {
                        b2Vec2 vertices[3];
                        vertices[0].Set(-0.1f, 0.0f);
                        vertices[1].Set(0.1f, 0.0f);
                        vertices[2].Set(0.0f, 1.5f);
                        m_polygons[1].Set(vertices, 3);
                }

                {
                        float w = 1.0f;
                        float b = w / (2.0f + b2Sqrt(2.0f));
                        float s = b2Sqrt(2.0f) * b;

                        b2Vec2 vertices[8];
                        vertices[0].Set(0.5f * s, 0.0f);
                        vertices[1].Set(0.5f * w, b);
                        vertices[2].Set(0.5f * w, b + s);
                        vertices[3].Set(0.5f * s, w);
                        vertices[4].Set(-0.5f * s, w);
                        vertices[5].Set(-0.5f * w, b + s);
                        vertices[6].Set(-0.5f * w, b);
                        vertices[7].Set(-0.5f * s, 0.0f);

                        m_polygons[2].Set(vertices, 8);
                }

                {
                        m_polygons[3].SetAsBox(0.5f, 0.5f);
                }

                {
                        m_circle.m_radius = 0.5f;
                }

                {
                        m_edge.SetTwoSided(b2Vec2(-1.0f, 0.0f), b2Vec2(1.0f, 0.0f));
                }

                m_bodyIndex = 0;
                memset(m_bodies, 0, sizeof(m_bodies));

                m_degrees = 0.0f;

                m_mode = e_closest;
        }

        void Create(int32 index)
        {
                if (m_bodies[m_bodyIndex] != NULL)
                {
                        m_world->DestroyBody(m_bodies[m_bodyIndex]);
                        m_bodies[m_bodyIndex] = NULL;
                }

                b2BodyDef bd;

                float x = RandomFloat(-10.0f, 10.0f);
                float y = RandomFloat(0.0f, 20.0f);
                bd.position.Set(x, y);
                bd.angle = RandomFloat(-b2_pi, b2_pi);

                if (index == 4)
                {
                        bd.angularDamping = 0.02f;
                }

                m_bodies[m_bodyIndex] = m_world->CreateBody(&bd);

                if (index < 4)
                {
                        b2FixtureDef fd;
                        fd.shape = m_polygons + index;
                        fd.friction = 0.3f;
                        fd.userData.pointer = index + 1;
                        m_bodies[m_bodyIndex]->CreateFixture(&fd);
                }
                else if (index < 5)
                {
                        b2FixtureDef fd;
                        fd.shape = &m_circle;
                        fd.friction = 0.3f;
                        fd.userData.pointer = index + 1;
                        m_bodies[m_bodyIndex]->CreateFixture(&fd);
                }
                else
                {
                        b2FixtureDef fd;
                        fd.shape = &m_edge;
                        fd.friction = 0.3f;
                        fd.userData.pointer = index + 1;

                        m_bodies[m_bodyIndex]->CreateFixture(&fd);
                }

                m_bodyIndex = (m_bodyIndex + 1) % e_maxBodies;
        }

        void DestroyBody()
        {
                for (int32 i = 0; i < e_maxBodies; ++i)
                {
                        if (m_bodies[i] != NULL)
                        {
                                m_world->DestroyBody(m_bodies[i]);
                                m_bodies[i] = NULL;
                                return;
                        }
                }
        }

        void UpdateUI() override
        {
                ImGui::SetNextWindowPos(ImVec2(10.0f, 100.0f));
                ImGui::SetNextWindowSize(ImVec2(210.0f, 285.0f));
                ImGui::Begin("Ray-cast Controls", nullptr, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);

                if (ImGui::Button("Shape 1"))
                {
                        Create(0);
                }

                if (ImGui::Button("Shape 2"))
                {
                        Create(1);
                }

                if (ImGui::Button("Shape 3"))
                {
                        Create(2);
                }

                if (ImGui::Button("Shape 4"))
                {
                        Create(3);
                }

                if (ImGui::Button("Shape 5"))
                {
                        Create(4);
                }

                if (ImGui::Button("Shape 6"))
                {
                        Create(5);
                }

                if (ImGui::Button("Destroy Shape"))
                {
                        DestroyBody();
                }

                ImGui::RadioButton("Any", &m_mode, e_any);
                ImGui::RadioButton("Closest", &m_mode, e_closest);
                ImGui::RadioButton("Multiple", &m_mode, e_multiple);

                ImGui::SliderFloat("Angle", &m_degrees, 0.0f, 360.0f, "%.0f");

                ImGui::End();
        }

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

                g_debugDraw.DrawString(5, m_textLine, "Shape 1 is intentionally ignored by the ray");
                m_textLine += m_textIncrement;
                switch (m_mode)
                {
                case e_closest:
                        g_debugDraw.DrawString(5, m_textLine, "Ray-cast mode: closest - find closest fixture along the ray");
                        break;
                
                case e_any:
                        g_debugDraw.DrawString(5, m_textLine, "Ray-cast mode: any - check for obstruction");
                        break;

                case e_multiple:
                        g_debugDraw.DrawString(5, m_textLine, "Ray-cast mode: multiple - gather multiple fixtures");
                        break;
                }

                m_textLine += m_textIncrement;

                float angle = b2_pi * m_degrees / 180.0f;
                float L = 11.0f;
                b2Vec2 point1(0.0f, 10.0f);
                b2Vec2 d(L * cosf(angle), L * sinf(angle));
                b2Vec2 point2 = point1 + d;

                if (m_mode == e_closest)
                {
                        RayCastClosestCallback callback;
                        m_world->RayCast(&callback, point1, point2);

                        if (callback.m_hit)
                        {
                                g_debugDraw.DrawPoint(callback.m_point, 5.0f, b2Color(0.4f, 0.9f, 0.4f));
                                g_debugDraw.DrawSegment(point1, callback.m_point, b2Color(0.8f, 0.8f, 0.8f));
                                b2Vec2 head = callback.m_point + 0.5f * callback.m_normal;
                                g_debugDraw.DrawSegment(callback.m_point, head, b2Color(0.9f, 0.9f, 0.4f));
                        }
                        else
                        {
                                g_debugDraw.DrawSegment(point1, point2, b2Color(0.8f, 0.8f, 0.8f));
                        }
                }
                else if (m_mode == e_any)
                {
                        RayCastAnyCallback callback;
                        m_world->RayCast(&callback, point1, point2);

                        if (callback.m_hit)
                        {
                                g_debugDraw.DrawPoint(callback.m_point, 5.0f, b2Color(0.4f, 0.9f, 0.4f));
                                g_debugDraw.DrawSegment(point1, callback.m_point, b2Color(0.8f, 0.8f, 0.8f));
                                b2Vec2 head = callback.m_point + 0.5f * callback.m_normal;
                                g_debugDraw.DrawSegment(callback.m_point, head, b2Color(0.9f, 0.9f, 0.4f));
                        }
                        else
                        {
                                g_debugDraw.DrawSegment(point1, point2, b2Color(0.8f, 0.8f, 0.8f));
                        }
                }
                else if (m_mode == e_multiple)
                {
                        RayCastMultipleCallback callback;
                        m_world->RayCast(&callback, point1, point2);
                        g_debugDraw.DrawSegment(point1, point2, b2Color(0.8f, 0.8f, 0.8f));

                        for (int32 i = 0; i < callback.m_count; ++i)
                        {
                                b2Vec2 p = callback.m_points[i];
                                b2Vec2 n = callback.m_normals[i];
                                g_debugDraw.DrawPoint(p, 5.0f, b2Color(0.4f, 0.9f, 0.4f));
                                g_debugDraw.DrawSegment(point1, p, b2Color(0.8f, 0.8f, 0.8f));
                                b2Vec2 head = p + 0.5f * n;
                                g_debugDraw.DrawSegment(p, head, b2Color(0.9f, 0.9f, 0.4f));
                        }
                }

#if 0
                // This case was failing.
                {
                        b2Vec2 vertices[4];
                        //vertices[0].Set(-22.875f, -3.0f);
                        //vertices[1].Set(22.875f, -3.0f);
                        //vertices[2].Set(22.875f, 3.0f);
                        //vertices[3].Set(-22.875f, 3.0f);

                        b2PolygonShape shape;
                        //shape.Set(vertices, 4);
                        shape.SetAsBox(22.875f, 3.0f);

                        b2RayCastInput input;
                        input.p1.Set(10.2725f,1.71372f);
                        input.p2.Set(10.2353f,2.21807f);
                        //input.maxFraction = 0.567623f;
                        input.maxFraction = 0.56762173f;

                        b2Transform xf;
                        xf.SetIdentity();
                        xf.position.Set(23.0f, 5.0f);

                        b2RayCastOutput output;
                        bool hit;
                        hit = shape.RayCast(&output, input, xf);
                        hit = false;

                        b2Color color(1.0f, 1.0f, 1.0f);
                        b2Vec2 vs[4];
                        for (int32 i = 0; i < 4; ++i)
                        {
                                vs[i] = b2Mul(xf, shape.m_vertices[i]);
                        }

                        g_debugDraw.DrawPolygon(vs, 4, color);
                        g_debugDraw.DrawSegment(input.p1, input.p2, color);
                }
#endif
        }

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

        int32 m_bodyIndex;
        b2Body* m_bodies[e_maxBodies];
        b2PolygonShape m_polygons[4];
        b2CircleShape m_circle;
        b2EdgeShape m_edge;
        float m_degrees;
        int32 m_mode;
};

static int testIndex = RegisterTest("Collision", "Ray Cast", RayCast::Create);