alpha maps

hannes d

hey i was wondering about alphas
if you have a 3d model for in game and its solid except a few parts
it feels like a waste to make an alphamap/opacitymap for that
but if you use a seperate material or make it into a seperate object then it uses extra drawcalls
so what would be a good solution?

repete

Alpha maps are not a waste of time, they are and can be a massive vert saver which I just found out recently. They can also be a pain to work with sometimes and work best for faking holes/space :poly121:

Remember that the detail is coming off your high poly so the possibilities are endless.

here is a thread I started on the topic:
http://www.polycount.com/forum/showthread.php?t=124852

cheers

hannes d

very interesting thread that you linked
but in your case alphas are very important
but i was wondering if it would be better to do a alpha for the whole model even though 95% is solid, or would it be wiser to use a seperate material/uv for the alpha details

if i am not mistaken using the alpha on the whole thing is 1 drawcall for the alpha, and x for the other maps, but with extra wasted texture size in the alpha

on the other hand a seperate material could save me a lot of texture space, but it needs a seperate UV, and uses x drawcalls for the first object, and x+1 drawcalls for the second detail alpha object

is saving texturespace and splitting the object worth the trouble or is it less optimised?

rollin

You always have to check how many scene objects with alpha overlap and if you have alpha test or alpha blend or any other simpler blending mode like add.

It totally depends on the model, the scene, the engine and the situation in game where this asset shows.

Most of the time you try to use alpha test (1 or 0 alpha, no smooth transition) and that not just on one little peace of the model.
So if you have a model with hair you can make the hair an extra object and give the body a non alpha material
aso.

passerby

Should be carfull with it there are a lot of cases where a little extra geo is a lot cheaper than use of a alpha map, since z sorting can take a long time if there is lots of alpha used in the scene.