what exactly does additive do

as it appeard or seemed to appear in kungfusquirel's electric beam tut does additive make any texture (with black in it) fade the black part out and the bright parts glow?????

does it do any other neat tricks

Not really. But it can be used on sprites as well.

I believe "additive" causes the engine to add the color of each pixel of the object being rendered to whatever is behind it, which would naturaly make black dissapear...

this is just a shot in the "dark"

but in my limited experience with additive, it makes a texture sort of glow, or seem brighter that any other render mode ..

if you were to use a lava liquid texture, and set it to any other mode, it would be a dim sort of fluid, but additive makes it appear hotter, more glowy..

well as i said, its just a thought.. :smile:

Nah, I think Tracer is right (for the most part- not sure thats how it works or not) but additive mostly makes black on a texture/sprite become transparent.

They're both right.

Additive literally adds the RGB values of a sprite to whatever is visible behind it.  In the case of black, this value is "0 0 0", effectively causing the black parts of a sprite to disappear and the dark parts to fade out.

But this effect is not adjusted by lighting, meaning that in a dark area the bright parts of an addivtive sprite will appear to glow (even in a totally black area, "0 0 0" + "255 255 255" = "255 255 255", i.e. pure white).

I have never seen 3 correct answers before

:razz: i had this incindent where i put an env_sprite and a light  in the same very spot. the light was 255 255 255 and the sprite was exit1.spr. the walls in the final map glowed with green-orange, aka the color of the sprite. i guess the color addition works with lights, too...

That would surprise me a great deal

It is a setting that makes a sprite with a black background not have the black background, but you have to tell it how invisible to make the black.