openGL_textured_triangle.cpp

#include <iostream>

#include "GL/glew.h"
#include "SDL2/SDL.h"
#include "SOIL.h"

const GLchar* vertexShaderSource = "#version 330 core\n"
    "layout (location = 0) in vec3 position;"
    "layout (location = 1) in vec2 texcoord;"
    "out vec2 Texcoord;"
    "void main()"
    "{"   
    "    Texcoord = texcoord;"
    "    gl_Position = vec4(position, 1.0);"
    "}";
const GLchar* fragmentShaderSource = "#version 330 core\n"
    "in vec2 Texcoord;"
    "out vec4 outColor;"
    "uniform sampler2D tex;"
    "void main()"
    "{"
    "    outColor = texture(tex, Texcoord);"
    "}";


int main()
{
	SDL_Init(SDL_INIT_VIDEO);

	SDL_Window* window = SDL_CreateWindow("window", 0, 0, 500, 500, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
	SDL_GLContext context = SDL_GL_CreateContext(window);   

    glewExperimental = GL_TRUE;
    glewInit();
 
    glViewport(0, 0, 500, 500);

	glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);	

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    GLint success;
    GLchar infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);

    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    GLfloat vertices[] = {
		//verts             //tex coords
        -0.5f, -0.5f, 0.0f, 0.0f, 0.0f,  
         0.5f, -0.5f, 0.0f, 0.5f, 1.0f, 
         0.0f,  0.5f, 0.0f, 1.0f, 0.0f   
    };

    GLuint VBO, VAO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    
    glBindVertexArray(VAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(0);

	//tex coords
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
	glEnableVertexAttribArray(1);

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

	//TEXTURE
	GLuint texture;
	glGenTextures(1, &texture);
	glBindTexture(GL_TEXTURE_2D, texture);
	
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	int width, height;
    unsigned char* image = SOIL_load_image("textures/awesomeface.png", &width, &height, 0, SOIL_LOAD_RGB);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
    glGenerateMipmap(GL_TEXTURE_2D);
    SOIL_free_image_data(image);

	bool quit = false;
	SDL_Event e;

	while(!quit){
        while( SDL_PollEvent( &e ) != 0 )
        {
            if( e.type == SDL_QUIT )
            {
                quit = true;
            }
        }

		SDL_GL_SwapWindow(window);	

		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
	    glClear(GL_COLOR_BUFFER_BIT);
	
		glUseProgram(shaderProgram);

	    glBindVertexArray(VAO);
	    glDrawArrays(GL_TRIANGLES, 0, 3);
	    glBindVertexArray(0);
    }

    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
 	SDL_GL_DeleteContext(context);
	SDL_DestroyWindow(window);
	SDL_Quit();
    return 0;
}