Help - Should I move to VBOs?

Graphics and GPU Programming Programming

Started by Gibbon_99 July 01, 2009 10:41 PM

13 comments, last by Gibbon_99 14 years, 9 months ago

813

July 17, 2009 10:13 PM

Notice the huge difference between your
glVertexPointer(2, GL_FLOAT, sizeof(myVertex), (const GLvoid *)&myQuad[0].x);

and that page's
glVertexPointer(2, GL_FLOAT, sizeof(myVertex), NULL);

NULL is the start address of the VBO.

Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);

Gibbon_99

122

Author

July 18, 2009 02:17 AM

Ok - that makes sense

So now it looks like

    glVertexPointer(2, GL_FLOAT, sizeof(myVertex), BUFFER_OFFSET(0)); //(const char *)&myQuad[0].x);    glTexCoordPointer(2, GL_FLOAT, sizeof(myVertex), BUFFER_OFFSET(sizeof(GLfloat) * 2)); //(const char *)&myQuad[0].s);

But now I get a seg fault on

glDrawArrays(GL_QUADS, 0, NUM_VERTS_SPLASH);

The page does mention that if you are using interleaved arrays - that you need to specify the stride in gl*Pointer.

Have I got sizeof(myVertex) right as the stride - The stride takes it from myQuad[0].x to the next coordindate myQuad[1].x - therefore the stride is the size needed to get to the start of the next vertex. Is that right??

Thanks for your help so far.

snoutmate

362

July 18, 2009 09:37 AM

Do you have the VBO bound before calling the gl*Pointer functions ?

ViperG

206

July 18, 2009 10:55 AM

Usually in 2D games, especially when drawing just quads etc, your bottle neck will be fill rate, not bandwidth of vertex data or anything of that sort. 10,000 polygons is nothing for a video card these days, so VBO probably wont help you. Maybe at 100,000 polygons or more, you might see a 5% improvement in performance from immediate mode to VBO. once you hit the 1 million polygon mark, this is when you need to be doing VBO 100%.

I've done a few tests, and anything under 10k polygons, a display list or vbo won't make a difference.

But you can always test it out, make a key that switches you from vbo to display list to immediate and see if your fps changes. (using framerate isn't always the best indicator for performance gains or changes... if you fps is less than 100 in both cases you should be fine... but framerates in the 300+ range become inaccurate and shouldn't be used for comparisons)

[Edited by - ViperG on July 18, 2009 3:55:01 PM]

Black Sky A Star Control 2/Elite like game

Gibbon_99

122

Author

July 18, 2009 07:13 PM

Quote:Original post by snoutmate
Do you have the VBO bound before calling the gl*Pointer functions ?

Works !! Changing from

glVertexPointer(2, GL_FLOAT, sizeof(myVertex), BUFFER_OFFSET(0)); glTexCoordPointer(2, GL_FLOAT, sizeof(myVertex), BUFFER_OFFSET(sizeof(GLfloat) * 2)); glBindBuffer(GL_ARRAY_BUFFER, splashVBOID);

glBindBuffer(GL_ARRAY_BUFFER, splashVBOID);glVertexPointer(2, GL_FLOAT, sizeof(myVertex), BUFFER_OFFSET(0)); glTexCoordPointer(2, GL_FLOAT, sizeof(myVertex), BUFFER_OFFSET(sizeof(GLfloat) * 2));

Thank you for your help !

Help - Should I move to VBOs?

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Help - Should I move to VBOs?

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines