Chapter 15 rendering artifacts

I’m getting these artifacts when running Chapter 15 provided final project on late 2013 rMBP 15" (GT 750m GPU)
Any ideas why this might be happening?


@mhorga Can you please help with when you get a chance? Thank you - much appreciated! :]

@bpashch - this looks like rendering artefacts from the morphing rocks. Unfortunately this seems to only happen on Nvidia GPUs and there aren’t any up-to-date drivers, and it appears Apple isn’t supporting them any more.

Go to GrassScene.swift and find setupRocks(instanceCount:). If you change

   let morphs = ["rock1", "rock2", "rock3"]


  let morphs = ["rock1"]

then it should work for you.

Alternatively, if you have a Metal-capable iOS device, if you reduce the instance numbers significantly, the morphing rocks should work on an iPhone.

(This happens in Chapter 13 too.)

Hi @caroline, appreciate the response

Regarding iOS - true, there’s no such problem.
And, as you mentioned, it does happen for chapter 13 project as well.

Setting just one morph for both rocks and grass does not seem to help (though it removes another kind of artifacts on the ground near the rocks).

I notice, though, that the artifacts on the .gif above disappear if I set instance count for grass to 10’000 instead of 200’000.

I find that interesting, as I’d expect that that would impact the FPS, but not something like artifacts.


Yes - the artefacts are from your Nvidia GPU. Apple and Nvidia seem to have parted ways, unfortunately. My MacBook Pro is 2015, which is also Nvidia and having artefacts in rendering, as well as losing OpenCL capability is disappointing.

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