Hi Guys

I have a weird issue on opengl. I am rendering a lot of tris (millions) using vertex arrays.

Here is the issue.

If I load up the tris and display as shaded with a constant color, the video memory is showing around 600MB.

If I then change the color array values to be varied at different vertex, the memory usage increases to around 1GB.

If I then spin the model around, the memory usage slowly decreases to around 600MB (after a couple of minutes).

But, if I load up the model straight away with varied shading, the memory is only 600MB.

This is on linux, so is it a driver issue ? Or is there something more obvious I am neglecting.

I am using nvidia-smi to check the graphics memory usage.

Cheers in advance for any help !

Hi

I am using the latest linux driver from Nvidia. The card is pretty old. Its an FX3800, but we see the same issue on an FX4000.

The same routines are used for both types of shading. I'm simply changing the values in the color array. Nothing else.

We get the same "doubling" of memory usage on smaller models too. Its like when the color array is updated, the memory

is not re-allocated on the card properly.

OK, the render code is basically as follows:

glShadeModel(GL_SMOOTH);

glEnable(GL_COLOR_MATERIAL)

glColorMaterial(GL_FRONT_AND_BACK,GL_AMBIENT);

glColorMaterial(GL_FRONT_AND_BACK,GL_SPECULAR);

glColorMaterial(GL_FRONT_AND_BACK,GL_DIFFUSE);

glEnableClientState(GL_VERTEX_ARRAY);

glVertexPointer(....);

glEnableClientState(GL_NORMAL_ARRAY);

glNormalPointer(...);

glEnableClientState(GL_COLOR_ARRAY);

glColorPointer(....);

glDrawElements(........);

So, I am just using arrays, not VBOs. All I do is update the values in the color array that glColorPointer points to before I come into this routine.

The problem is, on a 1GB graphics card, if I am using 600MB and then change the color, it swamps the card and

the system starts badly lagging because it is trying to double the memory usage.

Yes, sorry I forgot to add in the glDisableClientState commands. These are all deleted after the tris are drawn each time.

I added in VBOs and got the same effect even when deleting the VBO. Even simply using glBegin/End for the rendering (shock horror !!) causes the same effect.

It is kind of driving me crazy..................

Its all in C baby. I am not using anything like GLEW or SDL. Its pretty basic stuff.

Do you think it is a driver issue which is out of my control ??