GPU Stroke Rendering Issue
OS: macOS High Sierra 10.13.6 Build 17G5019
2 x Xeon E5-2690 v4 CPUs (don't ask ;) )
64 GB RAM
NVIDIA GeForce GTX 1080 8191 MB
GPU Driver Version: 3184.108.40.206.40.122
CUDA Driver Version: 418.105
Hi, I noticed a small rendering issue with strokes in GPU mode. The boundaries seem to be somewhat inaccurate, to the point that in certain situations (regardless of whether or not they're joined and by any method), suck as a tee shape, a small bulge of one stroke can appear beyond the edge of another, even though they shouldn't.
See attached pictures, the problem area is circled. It is subtle, but visible. There is a slight bulge extending outwards towards the right, presumably from the horizontal path at that junction. This is incorrect, the paths are joined and have identical stroke settings.
In CPU rendering, it renders correctly, and no bulge is visible. It seems to happen somewhat inconsistently, it doesn't always effect path junctions like that, only sometimes.
Also, the stroke width visibly changes slightly when switching between CPU and GPU mode. In my case, GPU mode seems to draw them slightly wider (higher stroke pt value) than it should be.
I wonder if this might be due to error introduced by using single precision floats on the GPU (which I assume is the case, considering how much lower double precision float performance is on most GPUs)? Who knows.
Regardless, the obvious workaround is to simply use CPU rendering, and it is relatively minor. But it is important to have an accurate representation of what you're doing.
Rene Andritsch commented
I think there are general rendering issues with paths. Look at my examples with GPU disabled and enabled. This is not good.
My specs are: MacBook Pro (15 Inch, 2018)
2,9 GHz Intel Core i9
32 GB 2400 MHz DDR4
Radeon Pro 560X 4096 MB
Intel UHD Graphics 630 1536 MB
MacOS Catalina 10.15.7
I"m having a similar issue. CPU view is way too slow, moving objects takes too long for screen to catchup, so I have to use GPU view - but unfortunately it sometimes decides that it cannot display a shape correctly and no matter what I do (rebuild shape, compound the path etc) it shows edges and thickness that simply isn't there.
Collin Anderson commented
I forgot to mention the version of Illustrator! 23.0.2