Sign in to follow this  

OpenGL Vertex Buffer Objects with Dynamic Data

Recommended Posts

Are there any good tutorials about using Vertex Buffer Objects properly with dynamic data? I want to render models where the vertices are recalculated each time (because I'm interpolating between frames), though the normals and texture coordinates are precalculated. I could understand that using VBOs for the vertices doesn't give any benefit, but I'm actually finding them slower than ordinary vertex arrays! First some performance figures. "Mixed" means that I'm using VBOs for the normals/texture-coords, but using an ordinary vertex array for the vertices. The figure in brackets is with normals disabled. Scene 1 - 700K triangles: No VBOs: 15FPS (19FPS) All VBOs: 15FPS (16FPS) Mixed: 28FPS (28FPS) Scene 2 - 130K triangles: No VBOs: 85FPS (110FPS) All VBOs: 85FPS (89FPS) Mixed: 178FPS (178FPS) Scene 3 - 772 triangles: No VBOs: 1200FPS (1200FPS) All VBOs: 1125FPS (1125FPS) Mixed: 1200FPS (1200FPS) So there are two things to conclude: - "Mixed" gives a significant advantage, presumably as the color/texture-coord data is cached on the gfx card rather than being sent each frame. But using a VBO for the vertices too loses this performance gain! - If normals are disabled, using a VBO for the vertices makes things slightly slower than not using VBOs at all. The code I'm using is: glGenBuffersARB( 1, &vbo_vertices ); glBindBufferARB( GL_ARRAY_BUFFER_ARB, vbo_vertices ); glBufferDataARB( GL_ARRAY_BUFFER_ARB, 3*n_vertices*sizeof(float), NULL, GL_STREAM_DRAW_ARB ); for initialisation, and then rendering each frame with: glBindBufferARB( GL_ARRAY_BUFFER_ARB, vbo_vertices ); glBufferSubDataARB( GL_ARRAY_BUFFER_ARB, 0, 3*n_vertices*sizeof(float), va_vertices_temp ); glVertexPointer(3, GL_FLOAT, 0, (char *)NULL); I've tried calling glBufferDataARB each frame to set the data, but that doesn't help. I'm using glDrawRangeElements to draw the arrays. Am I doing something wrong here? Or is this yet another case of VBOs being implemented poorly? I've looked at the many other threads on similar subjects, and can't see what I'm doing wrong. I've got a Radeon 9800, and have the latest OpenGL drivers. Okay, I can just use my "Mixed" method, and get a nice performance increase - but my reading from various forums is that this isn't the method I'm supposed to be using! Any ideas? thanks in advance, mark

Share this post

Link to post
Share on other sites
i sujjest searching these forums or the advanced forum theres been quite a few detailed discussions on it

Share this post

Link to post
Share on other sites
I guess your vertex array implementation is too good, so VBO cannot catch up :).
Have you tried map/umap instead of just copying new data into VBO?
Here is my note about VBO:

At the bottom, there is an example using map/unmap VBO. Try it on your system.

[Edited by - songho on March 6, 2006 2:38:14 PM]

Share this post

Link to post
Share on other sites

check out the MD2 loader example. It does basically the same thing you are doing, using VBO you *should* see a speed up (unless all of your data is dynamic, in which case you'll get similar performance to vertex arrays).

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