About decal actors... If it's a straight out masked decal with no transparency, wouldn't it be easier and better to use a flat card with a masked material on it instead of using Unreal's decal actor?
I'm not 200% sure on the best way to setup decals in UDK, so how I did it was, I plugged my decal texture into the emissive channel, and set the blend mode to blend_modulate, and lighting model MLM_Unlit. So it does work and is transparent, but I'd like to be able to adjust the OVERALL opacity of it so it isn't so dominant…
Are you actually using a decal material instead of a regular one? Normal materials cause the lighting to be incorrect on your decal. http://udn.epicgames.com/Three/UsingDecals.html
g3l - possibly. if you can then yeah thats going to be cheaper, however you might want to use a decal that spreads over two piece of geometry or that keeps the normals of the underlying pieces in which case its easier to use a decal. all depends on what you need it for and what your engine is setup to use.
that setup looks right to me - if you want control over the opacity then try plugging the texture into a power node before the emissive channel. if you make the exponent a material instance then you can adjust the overall visibility of the decal easily. for a white decal you need to overdrive the white values so they're…
well, i for myself make a mask for the decal, white what i want to be seen and black unseen, and plug it to the opacity mask slot (have to set the blend mode to masked). dunno if im doing it wrong, but works fine for me