Sure, the way it works is this:

you''ve got "source" pixels -- the pixels that have just been calculated and are ready to write to the framebuffer -- and "destination" pixels -- the pixels that are already on the framebuffer.

the first argument in glBlendFunc is the token describing how to use the source pixels, the second is how to use the destination pixels. GL_ONE, GL_ONE means literally multiply the source pixels by 1, then multiply the desination pixels by 1, then add them up and store them to the framebuffer. The add them up and store them is always the case, so it''s a matter of what you''re multiplying them by.

The valid tokens are:
GL_ONE (multiply by 1), GL_ZERO (multiply by 0), GL_DST_COLOR (multiply by the destination color), GL_ONE_MINUS_DST_COLOR (multiply by the inverse of the destination color), GL_SRC_ALPHA (multiply by the source alpha value), GL_ONE_MINUS_SRC_ALPHA (multiply by the inverse of the source alpha), GL_DST_ALPHA (multiply by the destination alpha), GL_ONE_MINUS_DST_ALPHA (multiply by the inverse of the destination alpha), GL_SRC_ALPHA_SATURATE (multiply by sourc alpha or inverse of destination alpha, whichever is less)

So GL_DST_COLOR, GL_ZERO means that you are essentially multiplying the source pixels by the destination pixels, then multiplying the destination pixels by zero, then adding them up and storing them.

GL_ONE, GL_ONE_MINUS_SRC_ALPHA is typical for a standard transparent effect. This means that you''re taking your full range of color from the source pixels, then multiplying the destination pixels by the inverse of the source alpha (thus knocking a black "hole" where there is high alpha in your source pixels), then adding them up. You can use GL_ALPHA, GL_ONE_MINUS_SRC_ALPHA which will multiply your source pixels by their alpha, but I prefer the "premultiplied" approach which assumes that your color has already been affected by alpha.

If you think about your colors as just being numbers and the blend functions as being math functions, it helps you realize how to group your effects and in what order you need to do things.

aaahhh!
now i see say''S the blind man.

thanks a mil!