GLFW and simple texture rendering example for C

[gomidas]

Hello, I am new with glfw. I compiled a sample code which is given on glfw doc. That renders a triangle. Now, I want to go one step forward and render a texture file (with stbi loader). I could not find enough tutorials for “C”. Can anyone help me for simple texture rendering ?

example page: GLFW: Getting started

I worked on a bit and modified code like this, in this case I do not see anything on screen, colorful triangle disappeared:

#include <glad/glad.h>
#define GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>
 
#include "linmath.h"
 
#include <stdlib.h>
#include <stdio.h>
 
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"


static const struct
{
    float x, y;
    float r, g, b;
} vertices[3] =
{
    { -0.6f, -0.4f, 1.f, 0.f, 0.f },
    {  0.6f, -0.4f, 0.f, 1.f, 0.f },
    {   0.f,  0.6f, 0.f, 0.f, 1.f }
};
 
static const char* vertex_shader_text =
"#version 330 core\n"
"layout(location = 0) in vec3 vertexPosition_modelspace;\n"
"layout(location = 1) in vec2 vertexUV;\n"
"uniform mat4 MVP;\n"
"out vec2 UV;\n"
"void main()\n"
"{\n"
"gl_Position = MVP * vec4(vertexPosition_modelspace, 1);\n"
"UV = vertexUV;\n"
"}\n";
 
static const char* fragment_shader_text =
"#version 330 core\n"
"in vec2 UV;\n"
"out vec3 color;\n"
"uniform sampler2D myTextureSampler;\n"
"void main()\n"
"{\n"
"    color = texture(myTextureSampler, UV).rgb;\n"
"}\n";
 
static void error_callback(int error, const char* description)
{
    fprintf(stderr, "Error: %s\n", description);
}
 
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GLFW_TRUE);
}

GLuint init_texture(char *imagepath)
{
    
    unsigned int width,height,nrChannels;
    unsigned char *data = stbi_load(imagepath, &width, &height, &nrChannels, STBI_rgb_alpha); 

    // Create one OpenGL texture
    GLuint textureID;
    glGenTextures(1, &textureID);

    // "Bind" the newly created texture : all future texture functions will modify this texture
    glBindTexture(GL_TEXTURE_2D, textureID);

    glTexImage2D(GL_TEXTURE_2D, 0,GL_RGBA, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
    // Read the file, call glTexImage2D with the right parameters
    //glfwLoadTexture2D(imagepath, 0);

    // Nice trilinear filtering.
    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_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    //glGenerateMipmap(GL_TEXTURE_2D);
    
    stbi_image_free(data);
    // Return the ID of the texture we just created
    return textureID;
}
 
int main(void)
{
    GLFWwindow* window;
    GLuint vertex_buffer, vertex_shader, fragment_shader, program;
    GLint mvp_location, vpos_location, vcol_location;
 
    glfwSetErrorCallback(error_callback);
 
    if (!glfwInit())
        exit(EXIT_FAILURE);
 
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
 
    window = glfwCreateWindow(640, 480, "Simple example", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        exit(EXIT_FAILURE);
    }
 
    glfwSetKeyCallback(window, key_callback);
 
    glfwMakeContextCurrent(window);
    gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);
    glfwSwapInterval(1);

    // NOTE: OpenGL error checks have been omitted for brevity
 
    glGenBuffers(1, &vertex_buffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
 
    vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex_shader, 1, &vertex_shader_text, NULL);
    glCompileShader(vertex_shader);
 
    fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment_shader, 1, &fragment_shader_text, NULL);
    glCompileShader(fragment_shader);
 
    program = glCreateProgram();
    glAttachShader(program, vertex_shader);
    glAttachShader(program, fragment_shader);
    glLinkProgram(program);
 
    mvp_location = glGetUniformLocation(program, "MVP");
    vpos_location = glGetAttribLocation(program, "vPos");
    vcol_location = glGetAttribLocation(program, "vCol");
 
    glEnableVertexAttribArray(vpos_location);
    glVertexAttribPointer(vpos_location, 2, GL_FLOAT, GL_FALSE,
                          sizeof(vertices[0]), (void*) 0);
    glEnableVertexAttribArray(vcol_location);
    glVertexAttribPointer(vcol_location, 3, GL_FLOAT, GL_FALSE,
                          sizeof(vertices[0]), (void*) (sizeof(float) * 2));
                          
    //Load Texure
    init_texture("lara.png");

    while (!glfwWindowShouldClose(window))
    {
        float ratio;
        int width, height;
        mat4x4 m, p, mvp;
 
        glfwGetFramebufferSize(window, &width, &height);
        ratio = width / (float) height;
 
        glViewport(0, 0, width, height);
        glClear(GL_COLOR_BUFFER_BIT);
 
        mat4x4_identity(m);
        mat4x4_rotate_Z(m, m, (float) glfwGetTime());
        mat4x4_ortho(p, -ratio, ratio, -1.f, 1.f, 1.f, -1.f);
        mat4x4_mul(mvp, p, m);
 
        glUseProgram(program);
        glUniformMatrix4fv(mvp_location, 1, GL_FALSE, (const GLfloat*) mvp);
        glDrawArrays(GL_TRIANGLES, 0, 3);
 
        glfwSwapBuffers(window);
        glfwPollEvents();
    }
 
    glfwDestroyWindow(window);
 
    glfwTerminate();
    exit(EXIT_SUCCESS);
}

What should I do ?

[CarstenT]

Still, you should do some more error-checking.
Do you have a glGetError() in the loop?

I’m not familiar with gladLoadGLLoader()
You should look into the errorchecking of the shaders. You can fish a status-report out… that’s what you left out, right? Check that program !==0

You may have to produce & use program before glBindBuffer …
You are missing a lot of bindings between
glUseProgram
and the draw-call.
This is the most obvious cause of error.