FBO to VBO

[michael84]

I'd like to dysplay 4 point via the VBO
I have my coordinate in the FBO.

I try the tutorial "render to vertex buffer" but I don't understand how does he manage to bind the data..for me it doesn't work

if someone has an example to send me.let me know!!

cheers,
Michael

[Reedbeta]

what tutorial are you talking about? link please... and please be more specific about how it "doesn't work". what happens? have you checked the glGetError output after each GL call?

[michael84]

this tutorial : http://www.devmaster.net/forums/showthread.php?t=7457
it is a tutorial from this forum.

I have an error in the glreadpixel
glReadPixels(0, 0, texSize, texSize, GL_RGBA, GL_FLOAT, 0);
checkGLErrors("read pixel vbo");

in the step4 of the tutorial (FBO to PBO), maybe because I use another time glReadPixel to use the data from the FBO to calculate other thing....

[Reedbeta]

well, come on then, what is the error?

[michael84]

the error is
OpenGL ERROR: invalid operation(Label: read pixel vbo)

[michael84]

with
glReadPixels(0, 0, texSize, 1, GL_RGBA, GL_FLOAT, 0);

I have no error but I think it is not right because i have 4 point to read
texSize equal 4

[Reedbeta]

Those two parameters are the width and height of the image to read. If you only want to read 4 pixels, you'll use either a 4x1 image or a 1x4 image. If you use a 4x4 image, you'll be reading 16 pixels.

[michael84]

ok thanks!
I didn't get this point before!