Sign in to follow this  

OpenGL OpenGL texture managing help needed

Recommended Posts

I'm trying to figure out how to create a texture manager in OpenGL. Previously I worked with DirectX and what I did there was the following: I created n number of containers that could t number of triangles of a specific type. ie a type would be defined by the material, texture etc used. everytime I render an object, it would be subdivided up into the appropriate container(s). when a container became full then I would empty it by rendering all items in the container to the screen. if at any point I needed more then n containers since a unique triangle was requested to be rendered then I would look through the n current containers and find the container that has the most amount of triangles in it. I would then render all items in that container and use it to hold the new triangle type. Now I was thinking of implementing the same sort of thing in OpenGL but I don't think I can because of the way that OpenGL works in comparison to DirectX. So my question is, how can I organize my data that I want to render, so that I minimize the number of texture loading/binding calls that are required to be done during each frame rendered. As an example, say that I have 3 objects made of of textures A, B, and C. What I would like to do is bind texture A, render each of the pieces of all the objects that contain texture A. Then bind texture B and render all the pieces in the scene that use texture B. Repeat for texture C. This way I am not switching multiple times between textures in one render call. Also in OpenGL, is there anyway to know how many textures I can stuff into the video memory at one time? For example in the previous case, if I can put textures A B and C all into the video memory at the same time, then it shouldn't matter how many times I bind to each one since the data doesn't have to transfer over to the graphics card each time.

Share this post

Link to post
Share on other sites
Nope, there is no way to know, once you upload the data to opengl (via the glTexImage() function) what happens to it is driver dependant.

It will probably endup in VRAM at "somepoint" however the swapping in and out operations are handled by the driver (I believe they use a Least-recently-used scheme to decide what stays in VRAM and what doesn't when space is needed) as is the "somepoint", it could be on first bind after the glTexImage call, it could be right after it, no one knows...

The scheme you outlined above however will work just as well with OGL as it did with DX, batching is still very much the order of the day.

To be honest, I'm not sure what 'differences' you are coming across between how OGL and D3D handle texture uploads...

Share this post

Link to post
Share on other sites
Original post by mmakrzem
Could you show me some pseudo code (or real code would be even better), on how I can batch render calls in OpenGL.

Not sure, but I am assuming he means use one texture call glBindTexture() and draw all polygons that use that texture with each object glDraw*(). And then move onto the next object and repeat as needed... That's my best guess.

Share this post

Link to post
Share on other sites
That's exactly what I am trying to achieve however I don't know how to structure my code so that I can "find" all polygons that use a specific texture/material. I don't want to search through all my scene objects for each texture/material since this will kill performance.

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  

  • Partner Spotlight

  • Forum Statistics

    • Total Topics
    • Total Posts
  • Similar Content

    • By xhcao
      Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness. 
    • By cebugdev
      hi guys, 
      are there any books, link online or any other resources that discusses on how to build special effects such as magic, lightning, etc. in OpenGL? i mean, yeah most of them are using particles but im looking for resources specifically on how to manipulate the particles to look like an effect that can be use for games,. i did fire particle before, and I want to learn how to do the other 'magic' as well.
      Like are there one book or link(cant find in google) that atleast featured how to make different particle effects in OpenGL (or DirectX)? If there is no one stop shop for it, maybe ill just look for some tips on how to make a particle engine that is flexible enough to enable me to design different effects/magic 
      let me know if you guys have recommendations.
      Thank you in advance!
    • By dud3
      How do we rotate the camera around x axis 360 degrees, without having the strange effect as in my video below? 
      Mine behaves exactly the same way spherical coordinates would, I'm using euler angles.
      Tried googling, but couldn't find a proper answer, guessing I don't know what exactly to google for, googled 'rotate 360 around x axis', got no proper answers.
      The video shows the difference between blender and my rotation:
    • By Defend
      I've had a Google around for this but haven't yet found some solid advice. There is a lot of "it depends", but I'm not sure on what.
      My question is what's a good rule of thumb to follow when it comes to creating/using VBOs & VAOs? As in, when should I use multiple or when should I not? My understanding so far is that if I need a new VBO, then I need a new VAO. So when it comes to rendering multiple objects I can either:
      * make lots of VAO/VBO pairs and flip through them to render different objects, or
      * make one big VBO and jump around its memory to render different objects. 
      I also understand that if I need to render objects with different vertex attributes, then a new VAO is necessary in this case.
      If that "it depends" really is quite variable, what's best for a beginner with OpenGL, assuming that better approaches can be learnt later with better understanding?
    • By test opty
      Hello all,
      On my Windows 7 x64 machine I wrote the code below on VS 2017 and ran it.
      #include <glad/glad.h>  #include <GLFW/glfw3.h> #include <std_lib_facilities_4.h> using namespace std; void framebuffer_size_callback(GLFWwindow* window , int width, int height) {     glViewport(0, 0, width, height); } //****************************** void processInput(GLFWwindow* window) {     if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)         glfwSetWindowShouldClose(window, true); } //********************************* int main() {     glfwInit();     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);     //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);     GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", nullptr, nullptr);     if (window == nullptr)     {         cout << "Failed to create GLFW window" << endl;         glfwTerminate();         return -1;     }     glfwMakeContextCurrent(window);     if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))     {         cout << "Failed to initialize GLAD" << endl;         return -1;     }     glViewport(0, 0, 600, 480);     glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);     glClearColor(0.2f, 0.3f, 0.3f, 1.0f);     glClear(GL_COLOR_BUFFER_BIT);     while (!glfwWindowShouldClose(window))     {         processInput(window);         glfwSwapBuffers(window);         glfwPollEvents();     }     glfwTerminate();     return 0; }  
      The result should be a fixed dark green-blueish color as the end of here. But the color of my window turns from black to green-blueish repeatedly in high speed! I thought it might be a problem with my Graphics card driver but I've updated it and it's: NVIDIA GeForce GTX 750 Ti.
      What is the problem and how to solve it please?
  • Popular Now