Sign in to follow this  

OpenGL [C++/OpenGL] Texture loading using a class goes wrong

Recommended Posts

Decrius    100
It worked, the texture loading, untill I made a class that would handle it =/ This is the class (only thr relevant code):
#include <iostream>
#include <GL/glfw.h>
#include <corona.h>

const int n_textures = 2;
char *texture_paths[2] = {"image.png", "image2.png"};

class Graphics
    GLuint textures[2];

    void draw_rect(GLuint, int, int, int, int);

        bool init(int, int);
        void resize();
        void draw();

    corona::Image *image;
    for (int i = 0; i < n_textures; i++)
        image = corona::OpenImage(texture_paths[i]);
        if (!image)
            //return false;

        glGenTextures(1, &textures[i]);
        glBindTexture(GL_TEXTURE_2D, textures[i]);

        //corona::PixelFormat format = image->getFormat();

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

        gluBuild2DMipmaps(GL_TEXTURE_2D, 3, image->getWidth(), image->getHeight(), GL_RGB, GL_UNSIGNED_BYTE, image->getPixels());
    delete image;

    glDeleteTextures(n_textures, textures);

bool Graphics::init(int width, int height)
    if(!glfwOpenWindow(width, height, 0, 0, 0, 0, 0, 0, GLFW_WINDOW))
        return false;
    glfwSetWindowTitle("GLFW Application");

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    return true;

void Graphics::resize()
    int width, height;
    glfwGetWindowSize(&width, &height);
    height = height > 0 ? height : 1;

    glViewport(0, 0, width, height);

    glOrtho(0.0f, width, 0.0f, height, -1.0f, 1.0f);


void Graphics::draw()

    draw_rect(textures[0], 100, 100, 200, 200);

void Graphics::draw_rect(GLuint texture, int x, int y, int w, int h)
    glBindTexture(GL_TEXTURE_2D, texture);
        glTexCoord2i(0, 0); glVertex2i(x, y);
        glTexCoord2i(1, 0); glVertex2i(x+w, y);
        glTexCoord2i(1, 1); glVertex2i(x+w, y+h);
        glTexCoord2i(0, 1); glVertex2i(x, y+h);

int main()
    Graphics graphics;
    graphics.init(512, 512);

    bool running = true;
    return 0;

The texture being displayed is white =/ while it should be a wonderfull coloured photo ^^. What is wrong? I guess the variables or something like that. I've tried almost every combination to get this to work, though it keeps displaying a white rectangle...while it worked perfect when it was just a simple function =/ Thanks! Decrius

Share this post

Link to post
Share on other sites
Brother Bob    10344
You load the textures in the constructor, and create the rendering context in the init function which must be called after the constructor if executed. That's your problem, you're trying to load textures without a rendering context.

Share this post

Link to post
Share on other sites
Trenki    345
First you should check for possible gl errors. A tool like glIntercept is very helpful in that. You will at least get one gl error when you set the texture mag filter since for the texture mag filter GL_LINEAR_MIPMAP_LINEAR is not supported!!! Only GL_NEAREST and GL_LINEAR is supported for the mag filter.

You should also not use gluBuild2DMipmaps (which makes the mipmaps in software but rather use the GL_SGIS_GENERATE_MIPMAP extension (there is also an EXT or whatever version of the extension and it has been integrated into the core OpenGL as well I think). It's just setting a texture parameter nothing more. You could also generate the mipmaps explicitly with a function call provided by the FBO extension.

You generally should use named internal formats preferable the sized ones insted of the numeric ones (second parameter in gluBuild2DMipmaps).

Share this post

Link to post
Share on other sites
Decrius    100
Ah thanks :), that worked...pretty straightforward...never thought of it like that =/

As for the extension you mention (rhyme!), I downloaded GLEW and loaded it into my application, but I'm a bit uncertain on how to use it.

glew.h defines three things:

#define GLEW_SGIS_generate_mipmap GLEW_GET_VAR(__GLEW_SGIS_generate_mipmap)

I guess I'll have to use the first two, but which one? And where to put it? In glTexParameterf() somewhere?


Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Similar Content

    • By Zaphyk
      I am developing my engine using the OpenGL 3.3 compatibility profile. It runs as expected on my NVIDIA card and on my Intel Card however when I tried it on an AMD setup it ran 3 times worse than on the other setups. Could this be a AMD driver thing or is this probably a problem with my OGL code? Could a different code standard create such bad performance?
    • By Kjell Andersson
      I'm trying to get some legacy OpenGL code to run with a shader pipeline,
      The legacy code uses glVertexPointer(), glColorPointer(), glNormalPointer() and glTexCoordPointer() to supply the vertex information.
      I know that it should be using setVertexAttribPointer() etc to clearly define the layout but that is not an option right now since the legacy code can't be modified to that extent.
      I've got a version 330 vertex shader to somewhat work:
      #version 330 uniform mat4 osg_ModelViewProjectionMatrix; uniform mat4 osg_ModelViewMatrix; layout(location = 0) in vec4 Vertex; layout(location = 2) in vec4 Normal; // Velocity layout(location = 3) in vec3 TexCoord; // TODO: is this the right layout location? out VertexData { vec4 color; vec3 velocity; float size; } VertexOut; void main(void) { vec4 p0 = Vertex; vec4 p1 = Vertex + vec4(Normal.x, Normal.y, Normal.z, 0.0f); vec3 velocity = (osg_ModelViewProjectionMatrix * p1 - osg_ModelViewProjectionMatrix * p0).xyz; VertexOut.velocity = velocity; VertexOut.size = TexCoord.y; gl_Position = osg_ModelViewMatrix * Vertex; } What works is the Vertex and Normal information that the legacy C++ OpenGL code seem to provide in layout location 0 and 2. This is fine.
      What I'm not getting to work is the TexCoord information that is supplied by a glTexCoordPointer() call in C++.
      What layout location is the old standard pipeline using for glTexCoordPointer()? Or is this undefined?
      Side note: I'm trying to get an OpenSceneGraph 3.4.0 particle system to use custom vertex, geometry and fragment shaders for rendering the particles.
    • By markshaw001
      Hi i am new to this forum  i wanted to ask for help from all of you i want to generate real time terrain using a 32 bit heightmap i am good at c++ and have started learning Opengl as i am very interested in making landscapes in opengl i have looked around the internet for help about this topic but i am not getting the hang of the concepts and what they are doing can some here suggests me some good resources for making terrain engine please for example like tutorials,books etc so that i can understand the whole concept of terrain generation.
    • By KarimIO
      Hey guys. I'm trying to get my application to work on my Nvidia GTX 970 desktop. It currently works on my Intel HD 3000 laptop, but on the desktop, every bind textures specifically from framebuffers, I get half a second of lag. This is done 4 times as I have three RGBA textures and one depth 32F buffer. I tried to use debugging software for the first time - RenderDoc only shows SwapBuffers() and no OGL calls, while Nvidia Nsight crashes upon execution, so neither are helpful. Without binding it runs regularly. This does not happen with non-framebuffer binds.
      GLFramebuffer::GLFramebuffer(FramebufferCreateInfo createInfo) { glGenFramebuffers(1, &fbo); glBindFramebuffer(GL_FRAMEBUFFER, fbo); textures = new GLuint[createInfo.numColorTargets]; glGenTextures(createInfo.numColorTargets, textures); GLenum *DrawBuffers = new GLenum[createInfo.numColorTargets]; for (uint32_t i = 0; i < createInfo.numColorTargets; i++) { glBindTexture(GL_TEXTURE_2D, textures[i]); GLint internalFormat; GLenum format; TranslateFormats(createInfo.colorFormats[i], format, internalFormat); // returns GL_RGBA and GL_RGBA glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, createInfo.width, createInfo.height, 0, format, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); DrawBuffers[i] = GL_COLOR_ATTACHMENT0 + i; glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + i, textures[i], 0); } if (createInfo.depthFormat != FORMAT_DEPTH_NONE) { GLenum depthFormat; switch (createInfo.depthFormat) { case FORMAT_DEPTH_16: depthFormat = GL_DEPTH_COMPONENT16; break; case FORMAT_DEPTH_24: depthFormat = GL_DEPTH_COMPONENT24; break; case FORMAT_DEPTH_32: depthFormat = GL_DEPTH_COMPONENT32; break; case FORMAT_DEPTH_24_STENCIL_8: depthFormat = GL_DEPTH24_STENCIL8; break; case FORMAT_DEPTH_32_STENCIL_8: depthFormat = GL_DEPTH32F_STENCIL8; break; } glGenTextures(1, &depthrenderbuffer); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); glTexImage2D(GL_TEXTURE_2D, 0, depthFormat, createInfo.width, createInfo.height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depthrenderbuffer, 0); } if (createInfo.numColorTargets > 0) glDrawBuffers(createInfo.numColorTargets, DrawBuffers); else glDrawBuffer(GL_NONE); if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) std::cout << "Framebuffer Incomplete\n"; glBindFramebuffer(GL_FRAMEBUFFER, 0); width = createInfo.width; height = createInfo.height; } // ... // FBO Creation FramebufferCreateInfo gbufferCI; gbufferCI.colorFormats =; gbufferCI.depthFormat = FORMAT_DEPTH_32; gbufferCI.numColorTargets = gbufferCFs.size(); gbufferCI.width = engine.settings.resolutionX; gbufferCI.height = engine.settings.resolutionY; gbufferCI.renderPass = nullptr; gbuffer = graphicsWrapper->CreateFramebuffer(gbufferCI); // Bind glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo); // Draw here... // Bind to textures glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, textures[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, textures[1]); glActiveTexture(GL_TEXTURE2); glBindTexture(GL_TEXTURE_2D, textures[2]); glActiveTexture(GL_TEXTURE3); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); Here is an extract of my code. I can't think of anything else to include. I've really been butting my head into a wall trying to think of a reason but I can think of none and all my research yields nothing. Thanks in advance!
    • By Adrianensis
      Hi everyone, I've shared my 2D Game Engine source code. It's the result of 4 years working on it (and I still continue improving features ) and I want to share with the community. You can see some videos on youtube and some demo gifs on my twitter account.
      This Engine has been developed as End-of-Degree Project and it is coded in Javascript, WebGL and GLSL. The engine is written from scratch.
      This is not a professional engine but it's for learning purposes, so anyone can review the code an learn basis about graphics, physics or game engine architecture. Source code on this GitHub repository.
      I'm available for a good conversation about Game Engine / Graphics Programming
  • Popular Now