GL_NV_texture_env_combine4 or Register combiners

Hi all,

For some vague reason I need to soften textures averaging nearby pixels, What I am trying to do is Draw a single Quad with the same texture bound to both the units with a small jitter in the texture coordinates. I do this multiple times to get an averaged pixel.
My math for the averaging at the pixel level is as follows

pixel = Texture0Weight0+Texture1Weight1

I can supply these Weight0 as Primary color of the fragment and Weight1 as a constant if I am going to use GL_NV_texture_env_combine4 or send it as the secondary color If I decide to use the Register combiners. My question here is, which technique would be faster, using the env combiners or the Register combiners. I can do this with just the first stage of the register combiner.

Could anybody let me know which one would yield faster results, or the penalty for using register combiners for this?

And does env_combine4 setup register combiners to do its job or does it use some other technique?


You would only need to use 1 General combiner stage, and this will most probably run at full speed same as Texture_env_combine4.

Texture_env_combine4 does probably use Register combiners internally, but that is of no concern really.


Any comments on this one Matt/Cass??

Also what is the fillrate when you use just one combiner?, Does the fillrate increase when the combiner is used only for multiplication like Mult/Mult/Sum?

I would like to know if using NV_Register_combiners is faster than NV_Env_Comine4 extn?



[This message has been edited by Sundy (edited 03-13-2002).]