multiple vbos

[M_Hax]

@aqnuep

In order to render shadows, you have to use shadow mapping in this case. What you have to do is the following:

Render your scene from the light’s direction using an orthogonal projection (taking in consideration you are using a directional light source) into a depth texture (without color buffers attached) using framebuffer objects.
The shader you use for the depth texture creation should be a simplified version of your sphere shader that keeps only the shape (discards should have effect) but not the lighting conditions as you don’t need them and rendering will be faster this way.
Then use the depth texture in the normal rendering pass to decide what is in shadow and what is not. For this, you have to calculate the vertex positions in the light’s orthogonal view space. Use these coordinates as texture coordinates to look up in the depth texture and that will tell you whether your fragment is in shadow or not.
This is simple shadow mapping, but in your case, because you want to use “volumetric” point sprites, it is not so simple but not that hard either.
What you have to do is after having the texture coordinates calculated for the shadow map per-point, you have to apply the appropriate offset in the fragment shader based on the shape of the sphere.

That’s some good explanation. I’ll try to look for some shadow mapping tutorials. Thanks again!