quote:Original post by oconnellseanm
Actually, the memory bandwidth stays the same I think no matter how many pixels are blocked by the alpha test. The alpha test isn''t performed until halfway into the pipeline, so its already been passed through memory into the GPU''s processor.

Not if you do the additive blending with the framebuffer.
The alpha-test prevents the blending from being performed for black pixels and saves you a read-from-fb, write-to-fb, which are quite costly.
You are right in saying that the AGP-bandwidth stays the same.

quote:Original post by lesni_bleble
i see.
but roam algorithm split far triangles, which uv and texture i have to use then?
or should i look for another terrain visualisation algorithm, which will be better suitable with texturing?

eL

You can use an object-linear texgen mode. This lets the OpenGL calculate the texure-coordinates from the object-space vertex positions.
You basicly scale the x/z-coordinate (assuming your terrain lies in the x/z-plane).
Google for automatic texture generation OpenGL or look it up in the red book.

Jan

Yes, but if you only sort the triangles by texture, you will get very weird popping once a triangle with texture A splits into two triangles with textures A and B.

You could always go for a hybrid approach by sorting by texture but putting a triangle into the VBO''s for all textures that influence it and then use the alpha-texture. This way, you save the T&L for the vertices that aren''t used at all by the texture.
Additionally, you get nice fading where different textures meet if you also add triangles close to the textured area.

Jan