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POOpengGl 4.2 Texture Mapping not displaying
 

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  1. POOpengGl 4.2 Texture Mapping not displaying
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    <p>I'm using cross-platform libraries (glfw, glew, glm) to make a simple texture mapping OpenGl Sample Program. It just takes an image from my computer, which is a 512 x 512 PNG, and is supposed to map it to a square I have displaying. The Program without the texture mapping works great and the square is visible. With the texture mapping Nothing is Visible, could you help me find where the mistake is?</p> <p>Edit: Perhaps I'm missing a binding or something within my "do" drawing-to-the-frame loop?</p> <p>Main Program (LoadShaders and stbi_Image are externally defined correctly)</p> <pre><code>if( !glfwInit() ) { fprintf( stderr, "Failed to initialize GLFW\n" ); return -1; } glfwWindowHint(GLFW_SAMPLES, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE); // Open a window and create its OpenGL context GLFWwindow* window = glfwCreateWindow (640, 480, "Hello Triangle", NULL, NULL); if(!window) { fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" ); glfwTerminate(); return -1; } glfwMakeContextCurrent(window); // Initialize GLEW glewExperimental = GL_TRUE; // Needed for core profile GLenum err = glewInit(); if (err != GLEW_OK) { fprintf(stderr, "Failed to initialize GLEW\n"); fprintf(stderr, "Error: %s\n", glewGetErrorString(err)); return -1; } const GLubyte* renderer = glGetString (GL_RENDERER); // get renderer string const GLubyte* version = glGetString (GL_VERSION); // version as a string printf ("Renderer: %s\n", renderer); printf ("OpenGL version supported %s\n", version); // tell GL to only draw onto a pixel if the shape is closer to the viewer glEnable (GL_DEPTH_TEST); // enable depth-testing glDepthFunc (GL_LESS); // depth-testing interprets a smaller value as "closer" // Ensure we can capture the escape key being pressed below glfwSetInputMode(window,GLFW_STICKY_KEYS,GL_TRUE ); // Create and compile our GLSL program from the shaders GLuint programID = LoadShaders( "SimpleVertexShader.vertexshader", "SimpleFragmentShader.fragmentshader" ); GLuint MatrixID = glGetUniformLocation(programID, "MVP"); // Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit &lt;-&gt; // 100 units glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f); // Camera matrix glm::mat4 View = glm::lookAt( glm::vec3(4,3,3), // Camera is at (4,3,3), in World Space glm::vec3(0,0,0), // and looks at the origin glm::vec3(0,1,0) // Head is up ); // Model matrix : an identity matrix (model will be at the origin) glm::mat4 Model = glm::mat4(1.0f); // Our ModelViewProjection : multiplication of our 3 matrices glm::mat4 MVP = Projection * View * Model; unsigned char* image_data; int x, y, n; char* file_name; file_name = "/home/syk435/Pictures/texture_sample.png"; int force_channels = 4; image_data = stbi_load(file_name, &amp;x, &amp;y, &amp;n, force_channels); if (!image_data) { fprintf (stderr, "ERROR: could not load %s\n", file_name); } //check if not normal dims if (x &amp; (x - 1) != 0 || y &amp; (y - 1) != 0) { fprintf (stderr, "WARNING: texture %s is not power-of-2 dimensions\n", file_name); } //invert to norm int width_in_bytes = x * 4; unsigned char *top = NULL; unsigned char *bottom = NULL; unsigned char temp = 0; int half_height = y / 2; for (int row = 0; row &lt; half_height; row++) { top = image_data + row * width_in_bytes; bottom = image_data + (y - row - 1) * width_in_bytes; for (int col = 0; col &lt; width_in_bytes; col++) { temp = *top; *top = *bottom; *bottom = temp; top++; bottom++; } } static const GLfloat g_vertex_buffer_data[] = { -0.75f,-0.75f,0.0f, -0.75f, 0.75f,0.0f, 0.75f,-0.75f,0.0f, 0.75f, 0.75f,0.0f, -0.75f, 0.75f,0.0f, 0.75f,-0.75f,0.0f, }; GLuint vertexbuffer; glGenBuffers(1, &amp;vertexbuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); // Dark blue background glClearColor(0.0f, 0.0f, 0.0f, 0.0f); GLuint vao; glGenVertexArrays(1, &amp;vao); glBindVertexArray(vao); //texture stuff unsigned int tex = 0; glGenTextures (1, &amp;tex); glActiveTexture (GL_TEXTURE0); glBindTexture (GL_TEXTURE_2D, tex); GLuint TextureID = glGetUniformLocation(programID, "basic_texture"); glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGBA, x, y, 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data ); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); float texcoords[] = { 0.0f, 0.0f, 0.0f, 1.0f, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 1.0, 0.0 }; unsigned int vt_vbo; glGenBuffers (1, &amp;vt_vbo); glBindBuffer (GL_ARRAY_BUFFER, vt_vbo); int dimensions = 2; // 2d data for texture coords int length = 6; // 6 vertices glBufferData ( GL_ARRAY_BUFFER, dimensions * length * sizeof (float), texcoords, GL_STATIC_DRAW ); do{ // Clear the screen glClear( GL_COLOR_BUFFER_BIT ); // Use our shader glUseProgram(programID); glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &amp;MVP[0][0]); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, tex); // Set our "myTextureSampler" sampler to user Texture Unit 0 glUniform1i(TextureID, 0); // 1rst attribute buffer : vertices glEnableVertexAttribArray(0); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glVertexAttribPointer( 0, // attribute 0 3, // size GL_FLOAT, // type GL_FALSE, // normalized? 0, // stride (void*)0 // array buffer offset ); // note: this is your existing VAO glEnableVertexAttribArray(1); glBindBuffer (GL_ARRAY_BUFFER, vt_vbo); // note: I assume that vertex positions are location 0 dimensions = 2; // 2d data for texture coords glVertexAttribPointer (1, dimensions, GL_FLOAT, GL_FALSE, 0, NULL); // Draw the triangle ! glDrawArrays(GL_TRIANGLES, 0, 6); // 3 indices starting at 0 -&gt; 1 triangle glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); // Swap buffers glfwSwapBuffers(window); } // Check if the ESC key was pressed or the window was closed while( glfwGetKey( window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &amp;&amp; window!=NULL ); // Close OpenGL window and terminate GLFW glfwTerminate(); // Cleanup VBO glDeleteBuffers(1, &amp;vertexbuffer); glDeleteBuffers(1, &amp;vt_vbo); glDeleteProgram(programID); glDeleteTextures(1, &amp;TextureID); glDeleteVertexArrays(1, &amp;vao); return 0; </code></pre> <p>VertexShader:</p> <pre><code>#version 420 // Input vertex data, different for all executions of this shader. layout (location = 0) in vec3 vertexPosition_modelspace; layout (location = 1) in vec2 vt; // per-vertex texture co-ords out vec2 texture_coordinates; uniform mat4 MVP; void main(){ gl_Position = MVP * vec4(vertexPosition_modelspace,1); texture_coordinates = vt; } </code></pre> <p>FragmentShader:</p> <pre><code>#version 420 // Ouput data //texture stuff in vec2 texture_coordinates; uniform sampler2D basic_texture; out vec3 frag_colour; void main() { frag_colour = texture2D(basic_texture, texture_coordinates).rgb; } </code></pre>
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    1. PTQuestion
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    1. USsyk435
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    1. COIf you are drawing to the default framebuffer, the texture has a signature of RGBA. Im not quite sure if this is an issue, but have you tried a vec4 as your fragment shader output?
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      1. POOpengGl 4.2 Texture Mapping not displaying
      1. USVengarioth
    2. COThank you for your reply, but yeah I tried that to no avail.
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      1. POOpengGl 4.2 Texture Mapping not displaying
      1. USsyk435
    3. COHave you considered using `glGetError` in your setup code to at least determine that your texture is correctly loaded? Why is `frag_colour` a `vec3` and not a `vec4`?
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      1. POOpengGl 4.2 Texture Mapping not displaying
      1. USBrett Hale
 

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