box2d_sys 0.2.1

// SPDX-FileCopyrightText: 2023 Erin Catto
// SPDX-License-Identifier: MIT

#include "draw.h"
#include "sample.h"
#include "settings.h"

#include "box2d/math_functions.h"

#include <GLFW/glfw3.h>

class ConvexHull : public Sample
{
public:
	enum
	{
		e_count = b2_maxPolygonVertices
	};

	explicit ConvexHull( Settings& settings )
		: Sample( settings )
	{
		if ( settings.restart == false )
		{
			g_camera.m_center = { 0.5f, 0.0f };
			g_camera.m_zoom = 25.0f * 0.3f;
		}

		m_generation = 0;
		m_auto = false;
		m_bulk = false;
		Generate();
	}

	void Generate()
	{
#if 0
		m_points[0] = { 5.65314484f, 0.204832315f };
		m_points[1] = {-5.65314484f, -0.204832315f };
		m_points[2] = {2.34463644f, 1.15731204f };
		m_points[3] = {0.0508846045f, 3.23230696f };
		m_points[4] = {-5.65314484f, -0.204832315f };
		m_points[5] = {-5.65314484f, -0.204832315f };
		m_points[6] = {3.73758054f, -1.11098099f };
		m_points[7] = {1.33504069f, -4.43795443f };

		m_count = e_count;
#elif 0
		m_points[0] = { -0.328125, 0.179688 };
		m_points[1] = { -0.203125, 0.304688 };
		m_points[2] = { 0.171875, 0.304688 };
		m_points[3] = { 0.359375, 0.117188 };
		m_points[4] = { 0.359375, -0.195313 };
		m_points[5] = { 0.234375, -0.320313 };
		m_points[6] = { -0.265625, -0.257813 };
		m_points[7] = { -0.328125, -0.132813 };

		b2Hull hull = b2ComputeHull( m_points, 8 );
		bool valid = b2ValidateHull( &hull );
		if ( valid == false )
		{
			assert( valid );
		}

		m_count = e_count;
#else

		float angle = b2_pi * RandomFloat();
		b2Rot r = b2MakeRot( angle );

		b2Vec2 lowerBound = { -4.0f, -4.0f };
		b2Vec2 upperBound = { 4.0f, 4.0f };

		for ( int 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 = b2Clamp( { x, y }, lowerBound, upperBound );
			m_points[i] = b2RotateVector( r, v );
		}

		m_count = e_count;
#endif

		m_generation += 1;
	}

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

			case GLFW_KEY_B:
				m_bulk = !m_bulk;
				break;

			case GLFW_KEY_G:
				Generate();
				break;

			default:
				break;
		}
	}

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

		g_draw.DrawString( 5, m_textLine, "Options: generate(g), auto(a), bulk(b)" );
		m_textLine += m_textIncrement;

		b2Hull hull;
		bool valid = false;
		float milliseconds = 0.0f;

		if ( m_bulk )
		{
#if 1
			// defect hunting
			for ( int i = 0; i < 10000; ++i )
			{
				Generate();
				hull = b2ComputeHull( m_points, m_count );
				if ( hull.count == 0 )
				{
					// m_bulk = false;
					// break;
					continue;
				}

				valid = b2ValidateHull( &hull );
				if ( valid == false || m_bulk == false )
				{
					m_bulk = false;
					break;
				}
			}
#else
			// performance
			Generate();
			b2Timer timer;
			for ( int i = 0; i < 1000000; ++i )
			{
				hull = b2ComputeHull( m_points, m_count );
			}
			valid = hull.count > 0;
			milliseconds = timer.GetMilliseconds();
#endif
		}
		else
		{
			if ( m_auto )
			{
				Generate();
			}

			hull = b2ComputeHull( m_points, m_count );
			if ( hull.count > 0 )
			{
				valid = b2ValidateHull( &hull );
				if ( valid == false )
				{
					m_auto = false;
				}
			}
		}

		if ( valid == false )
		{
			g_draw.DrawString( 5, m_textLine, "generation = %d, FAILED", m_generation );
			m_textLine += m_textIncrement;
		}
		else
		{
			g_draw.DrawString( 5, m_textLine, "generation = %d, count = %d", m_generation, hull.count );
			m_textLine += m_textIncrement;
		}

		if ( milliseconds > 0.0f )
		{
			g_draw.DrawString( 5, m_textLine, "milliseconds = %g", milliseconds );
			m_textLine += m_textIncrement;
		}

		m_textLine += m_textIncrement;

		g_draw.DrawPolygon( hull.points, hull.count, b2_colorGray );

		for ( int32_t i = 0; i < m_count; ++i )
		{
			g_draw.DrawPoint( m_points[i], 5.0f, b2_colorBlue );
			g_draw.DrawString( b2Add( m_points[i], { 0.1f, 0.1f } ), "%d", i );
		}

		for ( int32_t i = 0; i < hull.count; ++i )
		{
			g_draw.DrawPoint( hull.points[i], 6.0f, b2_colorGreen );
		}
	}

	static Sample* Create( Settings& settings )
	{
		return new ConvexHull( settings );
	}

	b2Vec2 m_points[b2_maxPolygonVertices];
	int32_t m_count;
	int32_t m_generation;
	bool m_auto;
	bool m_bulk;
};

static int sampleIndex = RegisterSample( "Geometry", "Convex Hull", ConvexHull::Create );