Dolphin, the GameCube and Wii emulator - Forums

I understand that but it was running poorly on OpenGL with the stable build, and the fact that there is so much of a difference between 2x to 2.5x IR suggests there's maybe more to this issue.

Most people with lower end GPUs like yours experienced similar drops. It's perfectly reasonable

A 25% increase in IR is significant, and enough so to cause that drop. Nothing's wrong, just your GPU can't handle 2.5 on that game.

25% IR results on 56% more pixels. As this would lead to more cache misses in the GPU, it's even more than a 56% slowdown

We have rewritten our shaders about a year ago. They are more accurate now, but requires a much better GPU, or you'll end with a lower IR on the same system. In the end, most mid-range desktop GPUs are fine to play at 4xIR, but mobile GPUs aren't as good :/

Oh okay, interesting stuff. What about AA, what is more demanding? Also is it true that that increasing IR requires more CPU power?

Some games have a slight CPU hit from IR, but it's mostly a GPU thing, and it more-or-less scales identically to SSAA - 2xIR has the same performance hit as 1xIR with 4xSSAA, 3xIR is like 1xIR with 9xSSAA. The main things to consider are that it'll look better to use a high IR and no AA until you have about as many pixels as are needed to cover your screen (3xIR covers 1080p pretty well) but beyond that it's kind of subjective and wonky - AA uses a better scaling filter than IR when you've got more samples than pixels on the screen, but most backends only have MSAA, so certain parts of a scene may not benefit at all.

What do you mean by "most" backends? Dolphin only has D3D and OGL, and D3D doesn't have SSAA, while OGL does.

I've been here for a long time, so briefly forgot that D3D9 isn't a thing any more.