Question by Hans D. · Oct 15, 2013 at 12:37 AM · ios performance alpha vertex overdraw

Should I increase tris and vertex in favor of reducing alpha overdraw for iOS?

So I've been reading a bit about iOS optimization, and a lot of people suggest reducing alpha overdraw is very important for the latest retina devices. I'm making a 2D game right now that utilizes bone animations from Maya, where the characters are separated in pieces and each piece is individually moved. I was wondering what's the better option:

Make every piece opaque to reduce alpha overdraw, but increase the tris and vertex count of each piece in the character by a considerable amount (since I have to basically trace the edge of each piece, which are often curves).
Make each piece a quad to reduce tris and vertex count but use transparency on everything.

Right now there's up to 18 characters on the screen at a time, each character is made by a single material with a texture atlas that contains all its pieces, achieving a single draw call per character. Each character is made up of around 15 pieces.

What do you think is the better trade off for the circumstances?

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Statement · Oct 28, 2013 at 02:26 PM 2

It's hard to tell but you're right in that alpha can be expensive. Have you tried replacing the transparent shaders with an opaque just to see how much you can possibly gain to begin with?