Add initial prototype.

3-mid/physics/implement/box2d/contrib/testbed/tests/breakable.cpp

@@ -0,0 +1,158 @@
+// 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 used to test sensor shapes.
+class Breakable : public Test
+{
+public:
+
+	enum
+	{
+		e_count = 7
+	};
+
+	Breakable()
+	{
+		// 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);
+		}
+
+		// Breakable dynamic body
+		{
+			b2BodyDef bd;
+			bd.type = b2_dynamicBody;
+			bd.position.Set(0.0f, 40.0f);
+			bd.angle = 0.25f * b2_pi;
+			m_body1 = m_world->CreateBody(&bd);
+
+			m_shape1.SetAsBox(0.5f, 0.5f, b2Vec2(-0.5f, 0.0f), 0.0f);
+			m_piece1 = m_body1->CreateFixture(&m_shape1, 1.0f);
+
+			m_shape2.SetAsBox(0.5f, 0.5f, b2Vec2(0.5f, 0.0f), 0.0f);
+			m_piece2 = m_body1->CreateFixture(&m_shape2, 1.0f);
+		}
+
+		m_break = false;
+		m_broke = false;
+	}
+
+	void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse) override
+	{
+		if (m_broke)
+		{
+			// The body already broke.
+			return;
+		}
+
+		// Should the body break?
+		int32 count = contact->GetManifold()->pointCount;
+
+		float maxImpulse = 0.0f;
+		for (int32 i = 0; i < count; ++i)
+		{
+			maxImpulse = b2Max(maxImpulse, impulse->normalImpulses[i]);
+		}
+
+		if (maxImpulse > 40.0f)
+		{
+			// Flag the body for breaking.
+			m_break = true;
+		}
+	}
+
+	void Break()
+	{
+		// Create two bodies from one.
+		b2Body* body1 = m_piece1->GetBody();
+		b2Vec2 center = body1->GetWorldCenter();
+
+		body1->DestroyFixture(m_piece2);
+		m_piece2 = NULL;
+
+		b2BodyDef bd;
+		bd.type = b2_dynamicBody;
+		bd.position = body1->GetPosition();
+		bd.angle = body1->GetAngle();
+
+		b2Body* body2 = m_world->CreateBody(&bd);
+		m_piece2 = body2->CreateFixture(&m_shape2, 1.0f);
+
+		// Compute consistent velocities for new bodies based on
+		// cached velocity.
+		b2Vec2 center1 = body1->GetWorldCenter();
+		b2Vec2 center2 = body2->GetWorldCenter();
+		
+		b2Vec2 velocity1 = m_velocity + b2Cross(m_angularVelocity, center1 - center);
+		b2Vec2 velocity2 = m_velocity + b2Cross(m_angularVelocity, center2 - center);
+
+		body1->SetAngularVelocity(m_angularVelocity);
+		body1->SetLinearVelocity(velocity1);
+
+		body2->SetAngularVelocity(m_angularVelocity);
+		body2->SetLinearVelocity(velocity2);
+	}
+
+	void Step(Settings& settings) override
+	{
+		if (m_break)
+		{
+			Break();
+			m_broke = true;
+			m_break = false;
+		}
+
+		// Cache velocities to improve movement on breakage.
+		if (m_broke == false)
+		{
+			m_velocity = m_body1->GetLinearVelocity();
+			m_angularVelocity = m_body1->GetAngularVelocity();
+		}
+
+		Test::Step(settings);
+	}
+
+	static Test* Create()
+	{
+		return new Breakable;
+	}
+
+	b2Body* m_body1;
+	b2Vec2 m_velocity;
+	float m_angularVelocity;
+	b2PolygonShape m_shape1;
+	b2PolygonShape m_shape2;
+	b2Fixture* m_piece1;
+	b2Fixture* m_piece2;
+
+	bool m_broke;
+	bool m_break;
+};
+
+static int testIndex = RegisterTest("Examples", "Breakable", Breakable::Create);