Texture Not Showing Up

Question

I am trying to add a texture onto my triangle but it just shows up as a black triangle. Here is my starting function that gets called:

GLuint vao;
GLuint shader_programme;
extern "C" void UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API createSimpleWindow()
{



    if (std::this_thread::get_id() == MAIN_THREAD_ID)
    {
        oldContext = glfwGetCurrentContext();

        newContext = glfwCreateWindow(640, 480, "window", NULL, oldContext);
        glfwMakeContextCurrent(newContext);
        // start GLEW extension handler
        glewExperimental = GL_TRUE;
        glewInit();

        glEnable(GL_DEPTH_TEST); // enable depth-testing
        glDepthFunc(GL_LESS); // depth-testing interprets a smaller value as "closer"
//triangle pts
        float points[] = {
            0.0f,  0.5f,  0.0f,     0.5f, 1.0f,
            0.5f, -0.5f,  0.0f,     1.0f, 0.0f,
            -0.5f, -0.5f,  0.0f,    0.0f, 0.0f
        };
        GLuint vbo = 0;
        glGenBuffers(1, &vbo);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(float), points, GL_STATIC_DRAW);

         vao = 0;
        glGenVertexArrays(1, &vao);
        glBindVertexArray(vao);
        //glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));
        glEnableVertexAttribArray(1);

        GLuint vs = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vs, 1, &vertex_shader, NULL);
        glCompileShader(vs);
        GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fs, 1, &fragment_shader, NULL);
        glCompileShader(fs);

        shader_programme = glCreateProgram();
        glAttachShader(shader_programme, fs);
        glAttachShader(shader_programme, vs);
        glLinkProgram(shader_programme);

         glUseProgram(shader_programme);
        glGenTextures(1, &texture);
        glBindTexture(GL_TEXTURE_2D, texture);
        int width, height, nrComponents;
        unsigned char *data = stbi_load("/Users/roma/Desktop/Escape Tech/BitBucketRepos/blankpluginGLFW/BlankPlugin/PluginSource/source/container2.png", &width, &height, &nrComponents, 0);

        writeToLog("before data");
        if (data) {
            writeToLog("data contained!!!!!!");
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        }
        glUniform1i(glGetUniformLocation(shader_programme, "texture1"), 0);
        //glfwCreateWindow(640, 480, "My Title", NULL, NULL);
        glfwSetKeyCallback(newContext, key_callback);
    }
    else
    {
        writeToLog("not main thread");
    }
}

Here is the function that gets called in a while loop:

extern "C" void UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API windowMainLoop()
{

    writeToLog("render loop");
    glfwMakeContextCurrent(newContext);
    glClearColor(0.0f, 1.0f, 1.0f, 1.0f);

    // loop until the window closed
    if (!glfwWindowShouldClose(newContext)) {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        if (std::this_thread::get_id() == MAIN_THREAD_ID)
        {
            // bind Texture
            glBindTexture(GL_TEXTURE_2D, texture);
            glUseProgram(shader_programme);
            glBindVertexArray(vao);
            // draw points 0-3 from the currently bound VAO with current in-use shader
            glDrawArrays(GL_TRIANGLES, 0, 3);
            glfwSwapBuffers(newContext);
            // poll the events
            glfwPollEvents();

        }
        //switch back to old context
        glfwMakeContextCurrent(oldContext);
        writeToLog("finished render loop");
    }

}

My "if (data)" statement results in the text begin written to the log so I know the image is being loaded properly but I cannot figure out why the triangle is black.

Any help would be greatly appreciated!

Answer 1

The issue is the setup arrays of generic vertex attribute data. Each attribute tuple consist of 5 components (x, y, z, u, v):

float points[] = {
    0.0f,  0.5f,  0.0f,    0.5f, 1.0f,
    0.5f, -0.5f,  0.0f,    1.0f, 0.0f,
   -0.5f, -0.5f,  0.0f,    0.0f, 0.0f
};

So the stride parameter has to be 5 * siezof(GLfloat) rather than 6 * siezof(GLfloat):

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);

---

The 2nd parameter of glBufferData is the size of the buffer in bytes. Your buffer consists of 15 (5 * 3) elements of type GLfloat. So the size is 15 * sizeof(float) rather than 9 * sizeof(float):

glBufferData(GL_ARRAY_BUFFER, 15 * sizeof(float), points, GL_STATIC_DRAW);

---

Since the format of the file is .png the last parameter of stbi_load should be set 4, to ensure that a 4 channels of the texture are get:

unsigned char *data = stbi_load("?.png", &width, &height, &nrComponents, 4);

The format and internal format of glTexImage2D have to be GL_RGBA.
By default the texture minifying function (GL_TEXTURE_MIN_FILTER) is GL_NEAREST_MIPMAP_LINEAR (see glTexParameteri). Since you don't use mip mapping, the parameter has to be changed to GL_LINEAR:

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);