new to OpenGLes, a few questions.

Question

hello, i am starting out with opengles coming from old opengl. i see there is no immediate mode anymore. so functions like glVertex glTexCoord are missing, right?

instead i have to use vertexarrays. right?

how can i modify the values of those arrays each frame?

for example, if i want to animate the texture coordinates, in old OpenGL i did:

  glTexCoord2f(x*time, y*time);

how can i achieve a similar effect with vertex arrays?

thanks!

Answer 1

Just update the arrays you pass to gl*Pointer, and draw again.

If you use VBOs, you'll need to update the VBO contents also.

Answer 2

if all you want to do is scroll the texture, there are direct ways to modify the texture coordinates as they go through the pipeline.

glMatrixMode( GL_TEXTURE );
glLoadIdentity();
glTranslatef(...);
glMatrixMode(...);

In general, cases where actual texcoord data should really change (as in because you want to apply a non-uniform transformation to them) are rare.