axmol/tests/cpp-tests/Classes/Box2DTestBed/tests/character_collision.cpp

// 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 typical character collision scenarios. This does not
/// show how you should implement a character in your application.
/// Instead this is used to test smooth collision on edge chains.
class CharacterCollision : public Test
{
public:
	CharacterCollision()
	{
		// Ground body
		{
			b2BodyDef bd;
			b2Body* ground = m_world->CreateBody(&bd);

			b2EdgeShape shape;
			shape.SetTwoSided(b2Vec2(-20.0f, 0.0f), b2Vec2(20.0f, 0.0f));
			ground->CreateFixture(&shape, 0.0f);
		}

		// Collinear edges with no adjacency information.
		// This shows the problematic case where a box shape can hit
		// an internal vertex.
		{
			b2BodyDef bd;
			b2Body* ground = m_world->CreateBody(&bd);

			b2EdgeShape shape;
			shape.SetTwoSided(b2Vec2(-8.0f, 1.0f), b2Vec2(-6.0f, 1.0f));
			ground->CreateFixture(&shape, 0.0f);
			shape.SetTwoSided(b2Vec2(-6.0f, 1.0f), b2Vec2(-4.0f, 1.0f));
			ground->CreateFixture(&shape, 0.0f);
			shape.SetTwoSided(b2Vec2(-4.0f, 1.0f), b2Vec2(-2.0f, 1.0f));
			ground->CreateFixture(&shape, 0.0f);
		}

		// Chain shape
		{
			b2BodyDef bd;
			bd.angle = 0.25f * b2_pi;
			b2Body* ground = m_world->CreateBody(&bd);

			b2Vec2 vs[4];
			vs[0].Set(5.0f, 7.0f);
			vs[1].Set(6.0f, 8.0f);
			vs[2].Set(7.0f, 8.0f);
			vs[3].Set(8.0f, 7.0f);
			b2ChainShape shape;
			shape.CreateLoop(vs, 4);
			ground->CreateFixture(&shape, 0.0f);
		}

		// Square tiles. This shows that adjacency shapes may
		// have non-smooth collision. There is no solution
		// to this problem.
		{
			b2BodyDef bd;
			b2Body* ground = m_world->CreateBody(&bd);

			b2PolygonShape shape;
			shape.SetAsBox(1.0f, 1.0f, b2Vec2(4.0f, 3.0f), 0.0f);
			ground->CreateFixture(&shape, 0.0f);
			shape.SetAsBox(1.0f, 1.0f, b2Vec2(6.0f, 3.0f), 0.0f);
			ground->CreateFixture(&shape, 0.0f);
			shape.SetAsBox(1.0f, 1.0f, b2Vec2(8.0f, 3.0f), 0.0f);
			ground->CreateFixture(&shape, 0.0f);
		}

		// Square made from an edge loop. Collision should be smooth.
		{
			b2BodyDef bd;
			b2Body* ground = m_world->CreateBody(&bd);

			b2Vec2 vs[4];
			vs[0].Set(-1.0f, 3.0f);
			vs[1].Set(1.0f, 3.0f);
			vs[2].Set(1.0f, 5.0f);
			vs[3].Set(-1.0f, 5.0f);
			b2ChainShape shape;
			shape.CreateLoop(vs, 4);
			ground->CreateFixture(&shape, 0.0f);
		}

		// Edge loop. Collision should be smooth.
		{
			b2BodyDef bd;
			bd.position.Set(-10.0f, 4.0f);
			b2Body* ground = m_world->CreateBody(&bd);

			b2Vec2 vs[10];
			vs[0].Set(0.0f, 0.0f);
			vs[1].Set(6.0f, 0.0f);
			vs[2].Set(6.0f, 2.0f);
			vs[3].Set(4.0f, 1.0f);
			vs[4].Set(2.0f, 2.0f);
			vs[5].Set(0.0f, 2.0f);
			vs[6].Set(-2.0f, 2.0f);
			vs[7].Set(-4.0f, 3.0f);
			vs[8].Set(-6.0f, 2.0f);
			vs[9].Set(-6.0f, 0.0f);
			b2ChainShape shape;
			shape.CreateLoop(vs, 10);
			ground->CreateFixture(&shape, 0.0f);
		}

		// Square character 1
		{
			b2BodyDef bd;
			bd.position.Set(-3.0f, 8.0f);
			bd.type = b2_dynamicBody;
			bd.fixedRotation = true;
			bd.allowSleep = false;

			b2Body* body = m_world->CreateBody(&bd);

			b2PolygonShape shape;
			shape.SetAsBox(0.5f, 0.5f);

			b2FixtureDef fd;
			fd.shape = &shape;
			fd.density = 20.0f;
			body->CreateFixture(&fd);
		}

		// Square character 2
		{
			b2BodyDef bd;
			bd.position.Set(-5.0f, 5.0f);
			bd.type = b2_dynamicBody;
			bd.fixedRotation = true;
			bd.allowSleep = false;

			b2Body* body = m_world->CreateBody(&bd);

			b2PolygonShape shape;
			shape.SetAsBox(0.25f, 0.25f);

			b2FixtureDef fd;
			fd.shape = &shape;
			fd.density = 20.0f;
			body->CreateFixture(&fd);
		}

		// Hexagon character
		{
			b2BodyDef bd;
			bd.position.Set(-5.0f, 8.0f);
			bd.type = b2_dynamicBody;
			bd.fixedRotation = true;
			bd.allowSleep = false;

			b2Body* body = m_world->CreateBody(&bd);

			float angle = 0.0f;
			float delta = b2_pi / 3.0f;
			b2Vec2 vertices[6];
			for (int32 i = 0; i < 6; ++i)
			{
				vertices[i].Set(0.5f * cosf(angle), 0.5f * sinf(angle));
				angle += delta;
			}

			b2PolygonShape shape;
			shape.Set(vertices, 6);

			b2FixtureDef fd;
			fd.shape = &shape;
			fd.density = 20.0f;
			body->CreateFixture(&fd);
		}

		// Circle character
		{
			b2BodyDef bd;
			bd.position.Set(3.0f, 5.0f);
			bd.type = b2_dynamicBody;
			bd.fixedRotation = true;
			bd.allowSleep = false;

			b2Body* body = m_world->CreateBody(&bd);

			b2CircleShape shape;
			shape.m_radius = 0.5f;

			b2FixtureDef fd;
			fd.shape = &shape;
			fd.density = 20.0f;
			body->CreateFixture(&fd);
		}

		// Circle character
		{
			b2BodyDef bd;
			bd.position.Set(-7.0f, 6.0f);
			bd.type = b2_dynamicBody;
			bd.allowSleep = false;

			m_character = m_world->CreateBody(&bd);

			b2CircleShape shape;
			shape.m_radius = 0.25f;

			b2FixtureDef fd;
			fd.shape = &shape;
			fd.density = 20.0f;
			fd.friction = 1.0f;
			m_character->CreateFixture(&fd);
		}
	}

	void Step(Settings& settings) override
	{
		b2Vec2 v = m_character->GetLinearVelocity();
		v.x = -5.0f;
		m_character->SetLinearVelocity(v);

		Test::Step(settings);
		DrawString(5, m_textLine, "This tests various character collision shapes.");
		
		DrawString(5, m_textLine, "Limitation: square and hexagon can snag on aligned boxes.");
		
		DrawString(5, m_textLine, "Feature: edge chains have smooth collision inside and out.");
		
	}

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

	b2Body* m_character;
};

static int testIndex = RegisterTest("Examples", "Character Collision", CharacterCollision::Create);