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Some rendering and gpu acceleration issues

Posted: Mon Jul 03, 2017 6:28 am
by cestarian
I made a (link) rendering comparison with a 1000x1000px sphere rendered in Krita, Photoshop and Paintstorm using each software's default airbrush. In creating this comparison I noticed several issues with Paintstorm that I am going to list out. Btw impressive work getting the airbrush quality so close to photoshop's, I like Paintstorm's results better actually because there is no noise texture like in the photoshop airbrush. For the record I am on Windows 7 x64 right now.
  • Paintstorm's Anti-Aliasing is less smooth than in Photoshop and Krita
  • If GPU acceleration is enabled, Anti-Aliasing gets disabled (there is no anti-aliasing)
  • If I use the airbrush with GPU Acceleration on, it will look fine at first, but after the canvas is refreshed severe banding will occur :?
By canvas refresh I mean for example if you hide and then show the layer, or if you crop the image, the canvas gets refreshed.

(link) Image example (Please view in full resolution, this displays both issues I'm talking about as seen just in paintstorm.)

Hope this gets fixed soon :mrgreen:

Re: Some rendering and gpu acceleration issues

Posted: Sun Jul 16, 2017 9:46 am
by support
I've tried to repeat this but there's no aliasing for me. I've used Round selection as a base of the sphere.

Also, I see a little gray border on the Krita 1st image sphere.

Re: Some rendering and gpu acceleration issues

Posted: Sun Jul 16, 2017 10:03 pm
by cestarian
That's strange, I just reinstalled Windows 7 (it was being funky, that aero issue seems to have (maybe) been fixed with the reinstall, if I encounter it again I'll try disabling vsync and let you know) but I still have this issue, maybe it's a bug that only happens on the 7? or with nvidia cards? (I've got a maxwell card)

This has definitely happened to me on two setups (albeit the same system) I'm gonna go try it out on my linux based laptop as well.... Yes, it happens there as well the same way as in my example.

Here's how I achieve this result.
  • Make a brush that has 100% opacity, 100% size, 100% color, 100% transparency and has it's softness curve set to 100% hard (so it's completely full)
  • Select a black color for the brush, white for the background
  • Click once with the mouse to create a black circle (which in paintstorm is aliased)
  • (I am not using the selection tool so that might be the reason you failed to reproduce this, only the brush tool)
The mouse is used to ensure steady 100% opacity focused on one point with no movement. (Since it's kinda hard to press 100% hard with a stylus without moving it around a little by accident).

And also as I said in my OP, even if you select the non-gpu mode there will still be aliasing which is not present in krita or photoshop, I don't know about the border in krita I have no explanation for it.

This happens to me under both linux and windows on separate machines so it's clearly not just a quirk in my machine. Both of them have an nvidia maxwell gpu. (Gtx 980-Ti and 950m) I have yet to try on my old kepler GPU based machine (although tomorrow that one will get replaced with a pascal)

The thing about the aliasing only appearing after I refreshed the canvas however was a quirk in my windows machine (seriously that bloody thing was breaking apart so I reinstalled windows 7 on it yesterday, I was super mad about needing to do that, but now I'm glad I did, so many issues disappeared...) right now I see it instantly, but the rest still stands, and across two versions of the program as well, and given that, you should be able to reproduce it. The common factor here might be the nvidia graphics card, are you perhaps on AMD?

Re: Some rendering and gpu acceleration issues

Posted: Fri Jul 21, 2017 10:11 am
by support
Make a brush that has 100% opacity, 100% size, 100% color, 100% transparency and has it's softness curve set to 100% hard (so it's completely full)
OK, now understand what you talking about. Don't use brush form to draw circle, this alising makes brush draw faster, control edge by the graph