I'm not sure that's true. One material with 2 textures is 1 draw call. Two materials with 1 texture each is 2 draw calls. And in forward rendering, that's also an extra draw call per material per per-pixel light (so for 2 per-pixel lights, we're now at 2 draw calls and 4 draw calls, respectively). And, depending on the…
Farfarer is right, texture calls is not draw calls. If you put 2 shaders/materials with the same texture they will still render 2 draw calls, but only one texture call on memory.
But to be fair rollin if we're talking about a character with two textures, one applied hands and head and the other applied torso and arms/legs then you're going to have two draw calls. In this example, anyway. Two maps will be one draw call if you use layering with two textures applied over all pixels, or write some code…
When I wrote my first post it seems I got caught in two minds and didn't fully type what I wanted to. I always seem to do this. I get distracted and don't fully explain my posts. The problem was I was trying to generalize a simple rule for draw calls where by if you use two textures across different sections leading to two…
"Premature optimization is the root of all evil." The best rules of thumb are to do things so they're not dumb and slow (there's no easy, clearly better solution) and then optimise as you go. You'll get 80% of your speed savings from fixing up 20% of your project - you just need to find the bottlenecks. If your game can't…