We are writing a benchmark program for OpenGL and have noticed a curiosity on the iPhone 6. Among other things we draw a bunch of trees and flowers, the same models but with different model matrices. If glDrawElementsInstanced is available we use it and if not we do it the old fashioned way with glDrawElements, one call for each tree and flower.
Most systems seem to benefit quite a lot from the instanced approach, but on the iPhone 6 (and the iPad Mini 2) we see a clear degrade in performance when drawing with instanced. (Systems that respond well includes both desktop, laptop and various android systems).
Is this a known issue or might we be doing something wrong, are there some special tricks to use or should be simply avoid instanced drawing on these platforms?