CODEWITHSUNDEEP
iosopengl-es-2.0glkview
user234736
user234736

Reputation:

How can I use GLKView to draw at a lower resolution?

I have an app based on "OpenGL Game" Xcode template, for everyday testing/dev I would like to render full screen but at lower resolution in simulator (e.g. 1/2 or 1/4). Any efficient/savvy way to put this in place?

(in case anybody wonder, I want to do this because my app is running very slow in simulator, so rendering at a smaller resolution would make testing/debugging a lot more programmer-friendly)

Upvotes: 0

Views: 826

Answers (1)

rickster
rickster

Reputation: 126127

The contentScaleFactor of the view is 2.0 by default on a Retina display. If you reduce the scale factor, GLKView automatically uses a smaller framebuffer and scales its contents up to screen size for display.

Scale factor 1.0 is half size (or the same number of pixels as a non-Retina screen). 0.5 would be quarter size — big, chunky pixels on any display. Non-integral scale factors between 1.0 and 2.0 work, too, and can be a great way to compromise between quality and performance on a Retina display.

Update: just had a vote remind me of this answer. I'm surprised I wouldn't have said this originally, but I may as well add it now...

The iOS Simulator runs OpenGL ES using a software renderer (i.e. on the host Mac's CPU, not its GPU). That's why it's slow. Performance characteristics and rendering results can vary from renderer to renderer, so never trust the simulator for anything OpenGL/GPU-related (except perhaps in very broad strokes).

Upvotes: 2

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