mobile_balanced.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"

class MobileBalanced : public Test
{
public:

        enum
        {
                e_depth = 4
        };

        MobileBalanced()
        {
                b2Body* ground;

                // Create ground body.
                {
                        b2BodyDef bodyDef;
                        bodyDef.position.Set(0.0f, 20.0f);
                        ground = m_world->CreateBody(&bodyDef);
                }

                float a = 0.5f;
                b2Vec2 h(0.0f, a);

                b2Body* root = AddNode(ground, b2Vec2_zero, 0, 3.0f, a);

                b2RevoluteJointDef jointDef;
                jointDef.bodyA = ground;
                jointDef.bodyB = root;
                jointDef.localAnchorA.SetZero();
                jointDef.localAnchorB = h;
                m_world->CreateJoint(&jointDef);
        }

        b2Body* AddNode(b2Body* parent, const b2Vec2& localAnchor, int32 depth, float offset, float a)
        {
                float density = 20.0f;
                b2Vec2 h(0.0f, a);

                b2Vec2 p = parent->GetPosition() + localAnchor - h;

                b2BodyDef bodyDef;
                bodyDef.type = b2_dynamicBody;
                bodyDef.position = p;
                b2Body* body = m_world->CreateBody(&bodyDef);

                b2PolygonShape shape;
                shape.SetAsBox(0.25f * a, a);
                body->CreateFixture(&shape, density);

                if (depth == e_depth)
                {
                        return body;
                }

                shape.SetAsBox(offset, 0.25f * a, b2Vec2(0, -a), 0.0f);
                body->CreateFixture(&shape, density);

                b2Vec2 a1 = b2Vec2(offset, -a);
                b2Vec2 a2 = b2Vec2(-offset, -a);
                b2Body* body1 = AddNode(body, a1, depth + 1, 0.5f * offset, a);
                b2Body* body2 = AddNode(body, a2, depth + 1, 0.5f * offset, a);

                b2RevoluteJointDef jointDef;
                jointDef.bodyA = body;
                jointDef.localAnchorB = h;

                jointDef.localAnchorA = a1;
                jointDef.bodyB = body1;
                m_world->CreateJoint(&jointDef);

                jointDef.localAnchorA = a2;
                jointDef.bodyB = body2;
                m_world->CreateJoint(&jointDef);

                return body;
        }

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

static int testIndex = RegisterTest("Solver", "Mobile Balanced", MobileBalanced::Create);