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Gazoo

OpenGL FBO on a GeForce 7600 GT

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Gazoo    122
Hello dear fellow forummers, Just a tad of info to let people know what this problem is related to - feel free to skip this paragraph. I'm currently involved in a project to simulate some AI on a GPU (Bee behavior to be exact), so I'll probably be popping my head in here ever so often as I am not the most cunning OpenGL programmer. During a recent GPU related project I read up a bit on pBuffers, but recently found out about this new FBO thingy. Now I'm the kind of guy that can't help getting my hands on the latest stuff so I though I'd incorporate this into my project - but I'm having some trouble... I've been following the excellent "OpenGL Frame Buffer Object 101" tutorial on this site as well as the an nvidia powerpoint presentation relating to the same issue (http://http.download.nvidia.com/developer/presentations/2005/GDC/OpenGL_Day/OpenGL_FrameBuffer_Object.pdf). Unfortunately however I am stuck at my program telling me that I'm using an unsupported frame buffer format. The "GL_FRAMEBUFFER_UNSUPPORTED_EXT" error code. I've tried being as faithful to the original tutorial and I am somewhat of a newb regarding these things - so I was hoping someone could clue me in to why this is failing? I thought the depth buffer used in the tutorial was pretty standard stuff. And seeing as the tutorial was written I (perhaps wrongly) assumed that this "new" graphics card would clearly support it. Perhaps I need to use something else? Any and all help is greatly appreciated. I have tried extracting and compromsing the minimal amount of code which I use in order to get the error:

// GlewTest.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>

//#define GLEW_STATIC 1
#include <GL/glew.h>
#include <gl/glut.h>
#include <cg/cgGL.h>
#include <cg/cg.h>

// Frame Buffer Object
GLuint fbo;

void initGLEW (void) {
    // init GLEW, obtain function pointers
    int err = glewInit();
    // Warning: This does not check if all extensions used 
    // in a given implementation are actually supported. 
    // Function entry points created by glewInit() will be 
    // NULL in that case!
    if (GLEW_OK != err) {
        printf((char*)glewGetErrorString(err));
        exit(-2);
    }
}

bool checkFramebufferStatus() {
    GLenum status;
    status=(GLenum)glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
    switch(status) {
        case GL_FRAMEBUFFER_COMPLETE_EXT:
            return true;
        case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:
            printf("Framebuffer incomplete,incomplete attachment\n");
            return false;
        case GL_FRAMEBUFFER_UNSUPPORTED_EXT:
            printf("Unsupported framebuffer format\n");
            return false;
        case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
            printf("Framebuffer incomplete,missing attachment\n");
            return false;
        case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
            printf("Framebuffer incomplete,attached images must have same dimensions\n");
            return false;
        case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
             printf("Framebuffer incomplete,attached images must have same format\n");
            return false;
        case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
            printf("Framebuffer incomplete,missing draw buffer\n");
            return false;
        case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
            printf("Framebuffer incomplete,missing read buffer\n");
            return false;
    }
	return false;
}


int _tmain(int argc, _TCHAR* argv[])
{
	// Unicode to Non-Unicode conversion
	char* nonunicodeargs = NULL;
	nonunicodeargs = new char[argc];
	wcstombs(nonunicodeargs, *argv, argc);
	//wcstombs_s(NULL, nonunicodeargs, argc, *argv, argc);
	printf("Unicode args converted to Non-Unicode.\n");

	// glut initializations
	glutInit(&argc, &nonunicodeargs);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);	// Depth buffer probably not necessary
	glutInitWindowPosition(-1,-1);							// Let window manager decide position
	glutInitWindowSize(512, 512);

	glutCreateWindow("3D Tech- GLUT Tutorial");
	printf("Display created.\n");

	initGLEW();

	// Generate Frame buffer so we can use it!
	//glGenFramebuffersEXT(1, &fbo);

	GLuint fb, depth_rb, tex;
	// create objects
	glGenFramebuffersEXT(1, &fb);// frame buffer
	glGenRenderbuffersEXT(1, &depth_rb);// render buffer
	glGenTextures(1, &tex);// texture
	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb);
	// initialize texture
	glBindTexture(GL_TEXTURE_2D, tex);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 512, 512, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
	// (set texture parameters here)
	// attach texture to framebuffercolor buffer
	glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex, 0);

	// initialize depth renderbuffer
	glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depth_rb);
	glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, 512, 512);
	// attach renderbufferto framebufferdepth buffer
	glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depth_rb);
	checkFramebufferStatus();


	int hest = 0;
	return 0;
}


As you may have noticed - I'm using VS2005... Once again - a thousand thanks in advance for any help... Regards, Gazoo

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_the_phantom_    11250
There are a couple of things which could be tripping it up;

- the filtering modes on the texture
- the depth of the depth buffer

The former you haven't included so I can't really guess at, the latter you can try changing GL_DEPTH_COMPONENT24 to either GL_DEPTH_COMPONENT16 or just plain GL_DEPTH_COMPONENT.

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Gazoo    122
Hey phantom,

Thanks a bunch - your reply helped me find the track to doing "something" that worked. I say "something" cause I'm not really sure why this is necessary...

I tried alternating the depth of the depth buffer which changed nothing - as for the filtering modes, I hadn't set any at all. Seeing as the tutorial didn't mention any, and seeing as I am a newb I didn't do anything else.

But searching the web and just blindly adding


glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);




seems to work. Can't say I understand it thou. I suppose it depends on what the default filtering is regarding the card one uses... Or?

Regards and thanks a lot,

Gazoo

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_the_phantom_    11250
I believe the filtering wasn't mentioned as it didn't appear to be a problem with the cards the article code was tested with, as the article code uses GL_LINEAR and works on both NV and ATI hardware.. so your problem is a little strange, I'll have to look into it when I get some time...

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