I’m trying to develop an app that uses opengl on android, and ideally make it run on any phone as old as the original droid (or at least any phone that has OpenGL ES 2.0 support). Currently, I’m using a 2048×2048 ETC1 texture compression. It works fine on the Droid X I’m testing it on, but I currently don’t have an original droid to test it on, and I can’t find much data on this topic either. I know the G1 didn’t do well with textures bigger than 512×512, and the droid seems to do fine with images as large as 1024×1024, but what about 2048×2048? (Again, etc1 compression, so it’s about 2 MB large). Also, because ETC1 doesn’t support alpha, I would like to load up another ETC1 texture to support an alpha channel. Is this a pipe dream?
Basically, I would like to know how much space I have to load texture data in android phones no older than the original droid, at least without the whole thing slowing down drastically.
You can query the MAX_TEXTURE_SIZE to get the maximum texture size, or you can look up your phone on http://glbenchmark.com (you can find the Droid info here). The G1 did not support GLES 2.0, AFAIK.
Loading up several textures should definitly work, especially when they are not more than 2 MB each. But you will of course be restricted by the size of the memory available.
Also, to have optimal performance you should mipmap your textures. Since you are using ETC, this must be done offline.
For a guide to how to use ETC1 with alpha, see here.