collision_filtering.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"
 
// This is a test of collision filtering.
// There is a triangle, a box, and a circle.
// There are 6 shapes. 3 large and 3 small.
// The 3 small ones always collide.
// The 3 large ones never collide.
// The boxes don't collide with triangles (except if both are small).
const int16     k_smallGroup = 1;
const int16 k_largeGroup = -1;
 
const uint16 k_triangleCategory = 0x0002;
const uint16 k_boxCategory = 0x0004;
const uint16 k_circleCategory = 0x0008;
 
const uint16 k_triangleMask = 0xFFFF;
const uint16 k_boxMask = 0xFFFF ^ k_triangleCategory;
const uint16 k_circleMask = 0xFFFF;
 
class CollisionFiltering : public Test
{
public:
        CollisionFiltering()
        {
                // Ground body
                {
                        b2EdgeShape shape;
                        shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
 
                        b2FixtureDef sd;
                        sd.shape = &shape;
                        sd.friction = 0.3f;
 
                        b2BodyDef bd;
                        b2Body* ground = m_world->CreateBody(&bd);
                        ground->CreateFixture(&sd);
                }
 
                // Small triangle
                b2Vec2 vertices[3];
                vertices[0].Set(-1.0f, 0.0f);
                vertices[1].Set(1.0f, 0.0f);
                vertices[2].Set(0.0f, 2.0f);
                b2PolygonShape polygon;
                polygon.Set(vertices, 3);
 
                b2FixtureDef triangleShapeDef;
                triangleShapeDef.shape = &polygon;
                triangleShapeDef.density = 1.0f;
 
                triangleShapeDef.filter.groupIndex = k_smallGroup;
                triangleShapeDef.filter.categoryBits = k_triangleCategory;
                triangleShapeDef.filter.maskBits = k_triangleMask;
 
                b2BodyDef triangleBodyDef;
                triangleBodyDef.type = b2_dynamicBody;
                triangleBodyDef.position.Set(-5.0f, 2.0f);
 
                b2Body* body1 = m_world->CreateBody(&triangleBodyDef);
                body1->CreateFixture(&triangleShapeDef);
 
                // Large triangle (recycle definitions)
                vertices[0] *= 2.0f;
                vertices[1] *= 2.0f;
                vertices[2] *= 2.0f;
                polygon.Set(vertices, 3);
                triangleShapeDef.filter.groupIndex = k_largeGroup;
                triangleBodyDef.position.Set(-5.0f, 6.0f);
                triangleBodyDef.fixedRotation = true; // look at me!
 
                b2Body* body2 = m_world->CreateBody(&triangleBodyDef);
                body2->CreateFixture(&triangleShapeDef);
 
                {
                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.position.Set(-5.0f, 10.0f);
                        b2Body* body = m_world->CreateBody(&bd);
 
                        b2PolygonShape p;
                        p.SetAsBox(0.5f, 1.0f);
                        body->CreateFixture(&p, 1.0f);
 
                        b2PrismaticJointDef jd;
                        jd.bodyA = body2;
                        jd.bodyB = body;
                        jd.enableLimit = true;
                        jd.localAnchorA.Set(0.0f, 4.0f);
                        jd.localAnchorB.SetZero();
                        jd.localAxisA.Set(0.0f, 1.0f);
                        jd.lowerTranslation = -1.0f;
                        jd.upperTranslation = 1.0f;
 
                        m_world->CreateJoint(&jd);
                }
 
                // Small box
                polygon.SetAsBox(1.0f, 0.5f);
                b2FixtureDef boxShapeDef;
                boxShapeDef.shape = &polygon;
                boxShapeDef.density = 1.0f;
                boxShapeDef.restitution = 0.1f;
 
                boxShapeDef.filter.groupIndex = k_smallGroup;
                boxShapeDef.filter.categoryBits = k_boxCategory;
                boxShapeDef.filter.maskBits = k_boxMask;
 
                b2BodyDef boxBodyDef;
                boxBodyDef.type = b2_dynamicBody;
                boxBodyDef.position.Set(0.0f, 2.0f);
 
                b2Body* body3 = m_world->CreateBody(&boxBodyDef);
                body3->CreateFixture(&boxShapeDef);
 
                // Large box (recycle definitions)
                polygon.SetAsBox(2.0f, 1.0f);
                boxShapeDef.filter.groupIndex = k_largeGroup;
                boxBodyDef.position.Set(0.0f, 6.0f);
 
                b2Body* body4 = m_world->CreateBody(&boxBodyDef);
                body4->CreateFixture(&boxShapeDef);
 
                // Small circle
                b2CircleShape circle;
                circle.m_radius = 1.0f;
 
                b2FixtureDef circleShapeDef;
                circleShapeDef.shape = &circle;
                circleShapeDef.density = 1.0f;
 
                circleShapeDef.filter.groupIndex = k_smallGroup;
                circleShapeDef.filter.categoryBits = k_circleCategory;
                circleShapeDef.filter.maskBits = k_circleMask;
 
                b2BodyDef circleBodyDef;
                circleBodyDef.type = b2_dynamicBody;
                circleBodyDef.position.Set(5.0f, 2.0f);
                
                b2Body* body5 = m_world->CreateBody(&circleBodyDef);
                body5->CreateFixture(&circleShapeDef);
 
                // Large circle
                circle.m_radius *= 2.0f;
                circleShapeDef.filter.groupIndex = k_largeGroup;
                circleBodyDef.position.Set(5.0f, 6.0f);
 
                b2Body* body6 = m_world->CreateBody(&circleBodyDef);
                body6->CreateFixture(&circleShapeDef);
        }
 
        static Test* Create()
        {
                return new CollisionFiltering;
        }
};
 
static int testIndex = RegisterTest("Examples", "Collision Filtering", CollisionFiltering::Create);