draw.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 "draw.h"
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>

#include "imgui/imgui.h"

#define BUFFER_OFFSET(x)  ((const void*) (x))

DebugDraw g_debugDraw;
Camera g_camera;

//
b2Vec2 Camera::ConvertScreenToWorld(const b2Vec2& ps)
{
        float w = float(m_width);
        float h = float(m_height);
        float u = ps.x / w;
        float v = (h - ps.y) / h;

        float ratio = w / h;
        b2Vec2 extents(ratio * 25.0f, 25.0f);
        extents *= m_zoom;

        b2Vec2 lower = m_center - extents;
        b2Vec2 upper = m_center + extents;

        b2Vec2 pw;
        pw.x = (1.0f - u) * lower.x + u * upper.x;
        pw.y = (1.0f - v) * lower.y + v * upper.y;
        return pw;
}

//
b2Vec2 Camera::ConvertWorldToScreen(const b2Vec2& pw)
{
        float w = float(m_width);
        float h = float(m_height);
        float ratio = w / h;
        b2Vec2 extents(ratio * 25.0f, 25.0f);
        extents *= m_zoom;

        b2Vec2 lower = m_center - extents;
        b2Vec2 upper = m_center + extents;

        float u = (pw.x - lower.x) / (upper.x - lower.x);
        float v = (pw.y - lower.y) / (upper.y - lower.y);

        b2Vec2 ps;
        ps.x = u * w;
        ps.y = (1.0f - v) * h;
        return ps;
}

// Convert from world coordinates to normalized device coordinates.
// http://www.songho.ca/opengl/gl_projectionmatrix.html
void Camera::BuildProjectionMatrix(float* m, float zBias)
{
        float w = float(m_width);
        float h = float(m_height);
        float ratio = w / h;
        b2Vec2 extents(ratio * 25.0f, 25.0f);
        extents *= m_zoom;

        b2Vec2 lower = m_center - extents;
        b2Vec2 upper = m_center + extents;

        m[0] = 2.0f / (upper.x - lower.x);
        m[1] = 0.0f;
        m[2] = 0.0f;
        m[3] = 0.0f;

        m[4] = 0.0f;
        m[5] = 2.0f / (upper.y - lower.y);
        m[6] = 0.0f;
        m[7] = 0.0f;

        m[8] = 0.0f;
        m[9] = 0.0f;
        m[10] = 1.0f;
        m[11] = 0.0f;

        m[12] = -(upper.x + lower.x) / (upper.x - lower.x);
        m[13] = -(upper.y + lower.y) / (upper.y - lower.y);
        m[14] = zBias;
        m[15] = 1.0f;
}

//
static void sCheckGLError()
{
        GLenum errCode = glGetError();
        if (errCode != GL_NO_ERROR)
        {
                fprintf(stderr, "OpenGL error = %d\n", errCode);
                assert(false);
        }
}

// Prints shader compilation errors
static void sPrintLog(GLuint object)
{
        GLint log_length = 0;
        if (glIsShader(object))
                glGetShaderiv(object, GL_INFO_LOG_LENGTH, &log_length);
        else if (glIsProgram(object))
                glGetProgramiv(object, GL_INFO_LOG_LENGTH, &log_length);
        else
        {
                fprintf(stderr, "printlog: Not a shader or a program\n");
                return;
        }

        char* log = (char*)malloc(log_length);

        if (glIsShader(object))
                glGetShaderInfoLog(object, log_length, NULL, log);
        else if (glIsProgram(object))
                glGetProgramInfoLog(object, log_length, NULL, log);

        fprintf(stderr, "%s", log);
        free(log);
}


//
static GLuint sCreateShaderFromString(const char* source, GLenum type)
{
        GLuint res = glCreateShader(type);
        const char* sources[] = { source };
        glShaderSource(res, 1, sources, NULL);
        glCompileShader(res);
        GLint compile_ok = GL_FALSE;
        glGetShaderiv(res, GL_COMPILE_STATUS, &compile_ok);
        if (compile_ok == GL_FALSE)
        {
                fprintf(stderr, "Error compiling shader of type %d!\n", type);
                sPrintLog(res);
                glDeleteShader(res);
                return 0;
        }

        return res;
}

// 
static GLuint sCreateShaderProgram(const char* vs, const char* fs)
{
        GLuint vsId = sCreateShaderFromString(vs, GL_VERTEX_SHADER);
        GLuint fsId = sCreateShaderFromString(fs, GL_FRAGMENT_SHADER);
        assert(vsId != 0 && fsId != 0);

        GLuint programId = glCreateProgram();
        glAttachShader(programId, vsId);
        glAttachShader(programId, fsId);
        glBindFragDataLocation(programId, 0, "color");
        glLinkProgram(programId);

        glDeleteShader(vsId);
        glDeleteShader(fsId);

        GLint status = GL_FALSE;
        glGetProgramiv(programId, GL_LINK_STATUS, &status);
        assert(status != GL_FALSE);

        return programId;
}

//
struct GLRenderPoints
{
        void Create()
        {
                const char* vs = \
                        "#version 330\n"
                        "uniform mat4 projectionMatrix;\n"
                        "layout(location = 0) in vec2 v_position;\n"
                        "layout(location = 1) in vec4 v_color;\n"
                        "layout(location = 2) in float v_size;\n"
                        "out vec4 f_color;\n"
                        "void main(void)\n"
                        "{\n"
                        "       f_color = v_color;\n"
                        "       gl_Position = projectionMatrix * vec4(v_position, 0.0f, 1.0f);\n"
                        "   gl_PointSize = v_size;\n"
                        "}\n";

                const char* fs = \
                        "#version 330\n"
                        "in vec4 f_color;\n"
                        "out vec4 color;\n"
                        "void main(void)\n"
                        "{\n"
                        "       color = f_color;\n"
                        "}\n";

                m_programId = sCreateShaderProgram(vs, fs);
                m_projectionUniform = glGetUniformLocation(m_programId, "projectionMatrix");
                m_vertexAttribute = 0;
                m_colorAttribute = 1;
                m_sizeAttribute = 2;

                // Generate
                glGenVertexArrays(1, &m_vaoId);
                glGenBuffers(3, m_vboIds);

                glBindVertexArray(m_vaoId);
                glEnableVertexAttribArray(m_vertexAttribute);
                glEnableVertexAttribArray(m_colorAttribute);
                glEnableVertexAttribArray(m_sizeAttribute);

                // Vertex buffer
                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
                glVertexAttribPointer(m_vertexAttribute, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_vertices), m_vertices, GL_DYNAMIC_DRAW);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
                glVertexAttribPointer(m_colorAttribute, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_colors), m_colors, GL_DYNAMIC_DRAW);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[2]);
                glVertexAttribPointer(m_sizeAttribute, 1, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_sizes), m_sizes, GL_DYNAMIC_DRAW);

                sCheckGLError();

                // Cleanup
                glBindBuffer(GL_ARRAY_BUFFER, 0);
                glBindVertexArray(0);

                m_count = 0;
        }

        void Destroy()
        {
                if (m_vaoId)
                {
                        glDeleteVertexArrays(1, &m_vaoId);
                        glDeleteBuffers(3, m_vboIds);
                        m_vaoId = 0;
                }

                if (m_programId)
                {
                        glDeleteProgram(m_programId);
                        m_programId = 0;
                }
        }

        void Vertex(const b2Vec2& v, const b2Color& c, float size)
        {
                if (m_count == e_maxVertices)
                        Flush();

                m_vertices[m_count] = v;
                m_colors[m_count] = c;
                m_sizes[m_count] = size;
                ++m_count;
        }

        void Flush()
        {
                if (m_count == 0)
                        return;

                glUseProgram(m_programId);

                float proj[16] = { 0.0f };
                g_camera.BuildProjectionMatrix(proj, 0.0f);

                glUniformMatrix4fv(m_projectionUniform, 1, GL_FALSE, proj);

                glBindVertexArray(m_vaoId);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(b2Vec2), m_vertices);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(b2Color), m_colors);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[2]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(float), m_sizes);

                glEnable(GL_PROGRAM_POINT_SIZE);
                glDrawArrays(GL_POINTS, 0, m_count);
                glDisable(GL_PROGRAM_POINT_SIZE);

                sCheckGLError();

                glBindBuffer(GL_ARRAY_BUFFER, 0);
                glBindVertexArray(0);
                glUseProgram(0);

                m_count = 0;
        }

        enum { e_maxVertices = 512 };
        b2Vec2 m_vertices[e_maxVertices];
        b2Color m_colors[e_maxVertices];
        float m_sizes[e_maxVertices];

        int32 m_count;

        GLuint m_vaoId;
        GLuint m_vboIds[3];
        GLuint m_programId;
        GLint m_projectionUniform;
        GLint m_vertexAttribute;
        GLint m_colorAttribute;
        GLint m_sizeAttribute;
};

//
struct GLRenderLines
{
        void Create()
        {
                const char* vs = \
                        "#version 330\n"
                        "uniform mat4 projectionMatrix;\n"
                        "layout(location = 0) in vec2 v_position;\n"
                        "layout(location = 1) in vec4 v_color;\n"
                        "out vec4 f_color;\n"
                        "void main(void)\n"
                        "{\n"
                        "       f_color = v_color;\n"
                        "       gl_Position = projectionMatrix * vec4(v_position, 0.0f, 1.0f);\n"
                        "}\n";

                const char* fs = \
                        "#version 330\n"
                        "in vec4 f_color;\n"
                        "out vec4 color;\n"
                        "void main(void)\n"
                        "{\n"
                        "       color = f_color;\n"
                        "}\n";

                m_programId = sCreateShaderProgram(vs, fs);
                m_projectionUniform = glGetUniformLocation(m_programId, "projectionMatrix");
                m_vertexAttribute = 0;
                m_colorAttribute = 1;

                // Generate
                glGenVertexArrays(1, &m_vaoId);
                glGenBuffers(2, m_vboIds);

                glBindVertexArray(m_vaoId);
                glEnableVertexAttribArray(m_vertexAttribute);
                glEnableVertexAttribArray(m_colorAttribute);

                // Vertex buffer
                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
                glVertexAttribPointer(m_vertexAttribute, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_vertices), m_vertices, GL_DYNAMIC_DRAW);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
                glVertexAttribPointer(m_colorAttribute, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_colors), m_colors, GL_DYNAMIC_DRAW);

                sCheckGLError();

                // Cleanup
                glBindBuffer(GL_ARRAY_BUFFER, 0);
                glBindVertexArray(0);

                m_count = 0;
        }

        void Destroy()
        {
                if (m_vaoId)
                {
                        glDeleteVertexArrays(1, &m_vaoId);
                        glDeleteBuffers(2, m_vboIds);
                        m_vaoId = 0;
                }

                if (m_programId)
                {
                        glDeleteProgram(m_programId);
                        m_programId = 0;
                }
        }

        void Vertex(const b2Vec2& v, const b2Color& c)
        {
                if (m_count == e_maxVertices)
                        Flush();

                m_vertices[m_count] = v;
                m_colors[m_count] = c;
                ++m_count;
        }

        void Flush()
        {
                if (m_count == 0)
                        return;

                glUseProgram(m_programId);

                float proj[16] = { 0.0f };
                g_camera.BuildProjectionMatrix(proj, 0.1f);

                glUniformMatrix4fv(m_projectionUniform, 1, GL_FALSE, proj);

                glBindVertexArray(m_vaoId);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(b2Vec2), m_vertices);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(b2Color), m_colors);

                glDrawArrays(GL_LINES, 0, m_count);

                sCheckGLError();

                glBindBuffer(GL_ARRAY_BUFFER, 0);
                glBindVertexArray(0);
                glUseProgram(0);

                m_count = 0;
        }

        enum { e_maxVertices = 2 * 512 };
        b2Vec2 m_vertices[e_maxVertices];
        b2Color m_colors[e_maxVertices];

        int32 m_count;

        GLuint m_vaoId;
        GLuint m_vboIds[2];
        GLuint m_programId;
        GLint m_projectionUniform;
        GLint m_vertexAttribute;
        GLint m_colorAttribute;
};

//
struct GLRenderTriangles
{
        void Create()
        {
                const char* vs = \
                        "#version 330\n"
                        "uniform mat4 projectionMatrix;\n"
                        "layout(location = 0) in vec2 v_position;\n"
                        "layout(location = 1) in vec4 v_color;\n"
                        "out vec4 f_color;\n"
                        "void main(void)\n"
                        "{\n"
                        "       f_color = v_color;\n"
                        "       gl_Position = projectionMatrix * vec4(v_position, 0.0f, 1.0f);\n"
                        "}\n";

                const char* fs = \
                        "#version 330\n"
                        "in vec4 f_color;\n"
                        "out vec4 color;\n"
                        "void main(void)\n"
                        "{\n"
                        "       color = f_color;\n"
                        "}\n";

                m_programId = sCreateShaderProgram(vs, fs);
                m_projectionUniform = glGetUniformLocation(m_programId, "projectionMatrix");
                m_vertexAttribute = 0;
                m_colorAttribute = 1;

                // Generate
                glGenVertexArrays(1, &m_vaoId);
                glGenBuffers(2, m_vboIds);

                glBindVertexArray(m_vaoId);
                glEnableVertexAttribArray(m_vertexAttribute);
                glEnableVertexAttribArray(m_colorAttribute);

                // Vertex buffer
                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
                glVertexAttribPointer(m_vertexAttribute, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_vertices), m_vertices, GL_DYNAMIC_DRAW);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
                glVertexAttribPointer(m_colorAttribute, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
                glBufferData(GL_ARRAY_BUFFER, sizeof(m_colors), m_colors, GL_DYNAMIC_DRAW);

                sCheckGLError();

                // Cleanup
                glBindBuffer(GL_ARRAY_BUFFER, 0);
                glBindVertexArray(0);

                m_count = 0;
        }

        void Destroy()
        {
                if (m_vaoId)
                {
                        glDeleteVertexArrays(1, &m_vaoId);
                        glDeleteBuffers(2, m_vboIds);
                        m_vaoId = 0;
                }

                if (m_programId)
                {
                        glDeleteProgram(m_programId);
                        m_programId = 0;
                }
        }

        void Vertex(const b2Vec2& v, const b2Color& c)
        {
                if (m_count == e_maxVertices)
                        Flush();

                m_vertices[m_count] = v;
                m_colors[m_count] = c;
                ++m_count;
        }

        void Flush()
        {
                if (m_count == 0)
                        return;

                glUseProgram(m_programId);

                float proj[16] = { 0.0f };
                g_camera.BuildProjectionMatrix(proj, 0.2f);

                glUniformMatrix4fv(m_projectionUniform, 1, GL_FALSE, proj);

                glBindVertexArray(m_vaoId);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(b2Vec2), m_vertices);

                glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
                glBufferSubData(GL_ARRAY_BUFFER, 0, m_count * sizeof(b2Color), m_colors);

                glEnable(GL_BLEND);
                glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
                glDrawArrays(GL_TRIANGLES, 0, m_count);
                glDisable(GL_BLEND);

                sCheckGLError();

                glBindBuffer(GL_ARRAY_BUFFER, 0);
                glBindVertexArray(0);
                glUseProgram(0);

                m_count = 0;
        }

        enum { e_maxVertices = 3 * 512 };
        b2Vec2 m_vertices[e_maxVertices];
        b2Color m_colors[e_maxVertices];

        int32 m_count;

        GLuint m_vaoId;
        GLuint m_vboIds[2];
        GLuint m_programId;
        GLint m_projectionUniform;
        GLint m_vertexAttribute;
        GLint m_colorAttribute;
};

//
DebugDraw::DebugDraw()
{
        m_showUI = true;
        m_points = NULL;
        m_lines = NULL;
        m_triangles = NULL;
}

//
DebugDraw::~DebugDraw()
{
        b2Assert(m_points == NULL);
        b2Assert(m_lines == NULL);
        b2Assert(m_triangles == NULL);
}

//
void DebugDraw::Create()
{
        m_points = new GLRenderPoints;
        m_points->Create();
        m_lines = new GLRenderLines;
        m_lines->Create();
        m_triangles = new GLRenderTriangles;
        m_triangles->Create();
}

//
void DebugDraw::Destroy()
{
        m_points->Destroy();
        delete m_points;
        m_points = NULL;

        m_lines->Destroy();
        delete m_lines;
        m_lines = NULL;

        m_triangles->Destroy();
        delete m_triangles;
        m_triangles = NULL;
}

//
void DebugDraw::DrawPolygon(const b2Vec2* vertices, int32 vertexCount, const b2Color& color)
{
        b2Vec2 p1 = vertices[vertexCount - 1];
        for (int32 i = 0; i < vertexCount; ++i)
        {
                b2Vec2 p2 = vertices[i];
                m_lines->Vertex(p1, color);
                m_lines->Vertex(p2, color);
                p1 = p2;
        }
}

//
void DebugDraw::DrawSolidPolygon(const b2Vec2* vertices, int32 vertexCount, const b2Color& color)
{
        b2Color fillColor(0.5f * color.r, 0.5f * color.g, 0.5f * color.b, 0.5f);

        for (int32 i = 1; i < vertexCount - 1; ++i)
        {
                m_triangles->Vertex(vertices[0], fillColor);
                m_triangles->Vertex(vertices[i], fillColor);
                m_triangles->Vertex(vertices[i + 1], fillColor);
        }

        b2Vec2 p1 = vertices[vertexCount - 1];
        for (int32 i = 0; i < vertexCount; ++i)
        {
                b2Vec2 p2 = vertices[i];
                m_lines->Vertex(p1, color);
                m_lines->Vertex(p2, color);
                p1 = p2;
        }
}

//
void DebugDraw::DrawCircle(const b2Vec2& center, float radius, const b2Color& color)
{
        const float k_segments = 16.0f;
        const float k_increment = 2.0f * b2_pi / k_segments;
        float sinInc = sinf(k_increment);
        float cosInc = cosf(k_increment);
        b2Vec2 r1(1.0f, 0.0f);
        b2Vec2 v1 = center + radius * r1;
        for (int32 i = 0; i < k_segments; ++i)
        {
                // Perform rotation to avoid additional trigonometry.
                b2Vec2 r2;
                r2.x = cosInc * r1.x - sinInc * r1.y;
                r2.y = sinInc * r1.x + cosInc * r1.y;
                b2Vec2 v2 = center + radius * r2;
                m_lines->Vertex(v1, color);
                m_lines->Vertex(v2, color);
                r1 = r2;
                v1 = v2;
        }
}

//
void DebugDraw::DrawSolidCircle(const b2Vec2& center, float radius, const b2Vec2& axis, const b2Color& color)
{
        const float k_segments = 16.0f;
        const float k_increment = 2.0f * b2_pi / k_segments;
        float sinInc = sinf(k_increment);
        float cosInc = cosf(k_increment);
        b2Vec2 v0 = center;
        b2Vec2 r1(cosInc, sinInc);
        b2Vec2 v1 = center + radius * r1;
        b2Color fillColor(0.5f * color.r, 0.5f * color.g, 0.5f * color.b, 0.5f);
        for (int32 i = 0; i < k_segments; ++i)
        {
                // Perform rotation to avoid additional trigonometry.
                b2Vec2 r2;
                r2.x = cosInc * r1.x - sinInc * r1.y;
                r2.y = sinInc * r1.x + cosInc * r1.y;
                b2Vec2 v2 = center + radius * r2;
                m_triangles->Vertex(v0, fillColor);
                m_triangles->Vertex(v1, fillColor);
                m_triangles->Vertex(v2, fillColor);
                r1 = r2;
                v1 = v2;
        }

        r1.Set(1.0f, 0.0f);
        v1 = center + radius * r1;
        for (int32 i = 0; i < k_segments; ++i)
        {
                b2Vec2 r2;
                r2.x = cosInc * r1.x - sinInc * r1.y;
                r2.y = sinInc * r1.x + cosInc * r1.y;
                b2Vec2 v2 = center + radius * r2;
                m_lines->Vertex(v1, color);
                m_lines->Vertex(v2, color);
                r1 = r2;
                v1 = v2;
        }

        // Draw a line fixed in the circle to animate rotation.
        b2Vec2 p = center + radius * axis;
        m_lines->Vertex(center, color);
        m_lines->Vertex(p, color);
}

//
void DebugDraw::DrawSegment(const b2Vec2& p1, const b2Vec2& p2, const b2Color& color)
{
        m_lines->Vertex(p1, color);
        m_lines->Vertex(p2, color);
}

//
void DebugDraw::DrawTransform(const b2Transform& xf)
{
        const float k_axisScale = 0.4f;
        b2Color red(1.0f, 0.0f, 0.0f);
        b2Color green(0.0f, 1.0f, 0.0f);
        b2Vec2 p1 = xf.p, p2;

        m_lines->Vertex(p1, red);
        p2 = p1 + k_axisScale * xf.q.GetXAxis();
        m_lines->Vertex(p2, red);

        m_lines->Vertex(p1, green);
        p2 = p1 + k_axisScale * xf.q.GetYAxis();
        m_lines->Vertex(p2, green);
}

//
void DebugDraw::DrawPoint(const b2Vec2& p, float size, const b2Color& color)
{
        m_points->Vertex(p, color, size);
}

//
void DebugDraw::DrawString(int x, int y, const char* string, ...)
{
        if (m_showUI == false)
        {
                return;
        }

        va_list arg;
        va_start(arg, string);
        ImGui::Begin("Overlay", NULL, ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoScrollbar);
        ImGui::SetCursorPos(ImVec2(float(x), float(y)));
        ImGui::TextColoredV(ImColor(230, 153, 153, 255), string, arg);
        ImGui::End();
        va_end(arg);
}

//
void DebugDraw::DrawString(const b2Vec2& pw, const char* string, ...)
{
        b2Vec2 ps = g_camera.ConvertWorldToScreen(pw);

        va_list arg;
        va_start(arg, string);
        ImGui::Begin("Overlay", NULL, ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoScrollbar);
        ImGui::SetCursorPos(ImVec2(ps.x, ps.y));
        ImGui::TextColoredV(ImColor(230, 153, 153, 255), string, arg);
        ImGui::End();
        va_end(arg);
}

//
void DebugDraw::DrawAABB(b2AABB* aabb, const b2Color& c)
{
        b2Vec2 p1 = aabb->lowerBound;
        b2Vec2 p2 = b2Vec2(aabb->upperBound.x, aabb->lowerBound.y);
        b2Vec2 p3 = aabb->upperBound;
        b2Vec2 p4 = b2Vec2(aabb->lowerBound.x, aabb->upperBound.y);

        m_lines->Vertex(p1, c);
        m_lines->Vertex(p2, c);

        m_lines->Vertex(p2, c);
        m_lines->Vertex(p3, c);

        m_lines->Vertex(p3, c);
        m_lines->Vertex(p4, c);

        m_lines->Vertex(p4, c);
        m_lines->Vertex(p1, c);
}

//
void DebugDraw::Flush()
{
        m_triangles->Flush();
        m_lines->Flush();
        m_points->Flush();
}