box-car-2d/GLEssentials/Drawer.cpp

//
//  Drawer.cpp
//  OSXGLEssentials
//
//  Created by Joshua Moerman on 10/03/14.
//
//

#include "Drawer.h"

#include <moggle/math/projection.hpp>
#include <moggle/math/transformation.hpp>

using namespace moggle;

// We need to pass relative addresses to opengl
#define BUFFER_OFFSET(i) ((char *)NULL + (i))

// We may assume this at some point
static_assert(sizeof(Vertex) == 6*4, "wrong size");

// Circles
static constexpr size_t circleVertices = 13;
static const Vertex::Position (&getCircle())[circleVertices]{
    static Vertex::Position vertices[circleVertices];
    static bool shouldInit = true;
    if(shouldInit){
        for(int i = 0; i < circleVertices;++i){
            auto phi = 2 * i / double(circleVertices-1) * M_PI;
            vertices[i] = {cos(phi), -sin(phi)};
        }
        shouldInit = false;
    }
    return vertices;
}

static const float viewSize = 20.0;

#if TARGET_OS_IPHONE
static const char * file = "/plain-iOS";
#else
static const char * file = "/plain";
#endif

// Implementation
Drawer::Drawer(std::string const & bundle){
    gl::enable(GL_BLEND);
    gl::blend_function(GL_SRC_ALPHA, GL_ONE);
    
    gl::clear_color(0.2f, 0.05f, 0.05f, 1.0f);
    
    projection = projection_matrices::orthographic(-viewSize, viewSize, -viewSize, viewSize, -1, 1);
    
    auto vertex = shader::from_file(shader_type::vertex, bundle + file + ".vsh");
    auto fragment = shader::from_file(shader_type::fragment, bundle + file + ".fsh");
    
    program.attach(vertex);
    program.attach(fragment);
    
    program.bind_attribute(0, "position");
    program.bind_attribute(1, "color");
    
    program.link();
    
    gl::generate_vertex_arrays(1, &vao);
    gl::bind_vertex_array(vao);
    
    gl::generate_buffers(1, &buf);
    gl::bind_buffer(GL_ARRAY_BUFFER, buf);
}

void Drawer::draw(){
    // bug when going to fullscreen
    // possibly related http://lists.apple.com/archives/mac-opengl/2012/Jul/msg00041.html
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    if(glGetError() != GL_NO_ERROR) return;
    
    matrix4<float> mvp = projection * transformation_matrices::translate(-camera);
    
    program.use();
    program.uniform<matrix4<float>>("mvp").set(mvp);
    
    if(!segments.empty()){
        if(verbose) printf("drawing %lu objects and %lu segments\n", sizes.size(), segments.size());
        
        gl::bind_vertex_array(vao);
        gl::bind_buffer(GL_ARRAY_BUFFER, buf);
        gl::buffer_data(GL_ARRAY_BUFFER, sizeof(Vertex) * segments.size(), &segments[0], GL_STATIC_DRAW);
        
        gl::enable_vertex_attribute_array(0);
        gl::enable_vertex_attribute_array(1);
        gl::vertex_attribute_pointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(0));
        gl::vertex_attribute_pointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(3*4));
        
        GLuint start = 0;
        for(auto&& s : sizes){
            gl::draw_arrays(GL_LINE_LOOP, start, s);
            start += s;
        }
    }
}

void Drawer::clear(){
    sizes.clear();
    segments.clear();
}

void Drawer::resize(float width, float height){
    auto aspect = width / height;
    auto hheight = viewSize;
    projection = projection_matrices::orthographic(-hheight * aspect, hheight * aspect, -hheight, hheight, -5, 5);
}

void Drawer::DrawPolygon(const b2Vec2* vertices, int32 vertexCount, const b2Color& color){
    if(verbose) printf("polygon (not solid)\n  %d vertices\n  %f %f %f\n", vertexCount, color.r, color.g, color.b);
    for(int i = 0; i < vertexCount; ++i){
        segments.push_back(Vertex{convert(vertices[i]), convert(color)});
    }
    sizes.emplace_back(vertexCount);
}

void Drawer::DrawSolidPolygon(const b2Vec2* vertices, int32 vertexCount, const b2Color& color){
    if(verbose) printf("polygon (solid, deferred)\n");
    DrawPolygon(vertices, vertexCount, color);
}

void Drawer::DrawCircle(const b2Vec2& center, float32 radius, const b2Color& color){
    if(verbose) printf("circle (not solid)\n  at %f %f (%f)\n  %f %f %f\n", center.x, center.y, radius, color.r, color.g, color.b);
    for(auto&& p : getCircle()){
        segments.push_back(Vertex{convert(center) + radius * p, convert(color)});
    }
    sizes.emplace_back(circleVertices);
}

void Drawer::DrawSolidCircle(const b2Vec2& center, float32 radius, const b2Vec2& axis, const b2Color& color){
    if(verbose) printf("circle (solid, deferred)\n");
    segments.push_back(Vertex{convert(center) - radius * convert(axis), convert(color)});
    segments.push_back(Vertex{convert(center) + radius * convert(axis), convert(color)});
    sizes.push_back(2);
    DrawCircle(center, radius, color);
}

void Drawer::DrawSegment(const b2Vec2& p1, const b2Vec2& p2, const b2Color& color){
    if(verbose) printf("segment\n  %f %f -> %f %f\n  %f %f %f\n", p1.x, p1.y, p2.x, p2.y, color.r, color.g, color.b);
    segments.push_back(Vertex{convert(p1), convert(color)});
    segments.push_back(Vertex{convert(p2), convert(color)});
    sizes.emplace_back(2);
}

void Drawer::DrawTransform(const b2Transform& xf){
    if(verbose) printf("transform\n");
}