convex_hull.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 ConvexHull : public Test
{
public:
        enum
        {
                e_count = b2_maxPolygonVertices
        };

        ConvexHull()
        {
                Generate();
                m_auto = false;
        }

        void Generate()
        {
                b2Vec2 lowerBound(-8.0f, -8.0f);
                b2Vec2 upperBound(8.0f, 8.0f);

                for (int32 i = 0; i < e_count; ++i)
                {
                        float x = 10.0f * RandomFloat();
                        float y = 10.0f * RandomFloat();

                        // Clamp onto a square to help create collinearities.
                        // This will stress the convex hull algorithm.
                        b2Vec2 v(x, y);
                        v = b2Clamp(v, lowerBound, upperBound);
                        m_points[i] = v;
                }

                m_count = e_count;
        }

        void Keyboard(int key) override
        {
                switch (key)
                {
                case GLFW_KEY_A:
                        m_auto = !m_auto;
                        break;

                case GLFW_KEY_G:
                        Generate();
                        break;
                }
        }

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

                b2PolygonShape shape;
                shape.Set(m_points, m_count);

                g_debugDraw.DrawString(5, m_textLine, "Press g to generate a new random convex hull");
                m_textLine += m_textIncrement;

                g_debugDraw.DrawPolygon(shape.m_vertices, shape.m_count, b2Color(0.9f, 0.9f, 0.9f));

                for (int32 i = 0; i < m_count; ++i)
                {
                        g_debugDraw.DrawPoint(m_points[i], 3.0f, b2Color(0.3f, 0.9f, 0.3f));
                        g_debugDraw.DrawString(m_points[i] + b2Vec2(0.05f, 0.05f), "%d", i);
                }

                if (shape.Validate() == false)
                {
                        m_textLine += 0;
                }

                if (m_auto)
                {
                        Generate();
                }
        }

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

        b2Vec2 m_points[b2_maxPolygonVertices];
        int32 m_count;
        bool m_auto;
};

static int testIndex = RegisterTest("Geometry", "Convex Hull", ConvexHull::Create);