Possible Direct3D scaling issue

[AlexC]

Hi Tony,

There is a minor D3D rendering issue I noticed which doesn't happen with DirectDraw, and I was able to notice it with all the 3.3.0.0 beta versions since uae.gfx started working in OS4, as that feature made it possible to use 1080p resolution.
If it already happened with earlier betas I wouldn't know as with the PicassoIV emulation I couldn't get more than 1280x960, making the display too blurry to notice minor artifacts.

I made some B/W background patterns to better illustrate the issue, and as can be seen on the attached screenshots (which are resized to 200% to make it easier to see) there are some horizontal "stretching" artifacts on the column spawning the first 120 pixels or so.

Without the special pattern it's not as pronounced, but still causes the fonts of icon names, Project menu and text editors to look uneven, as can be seen on the WB titlebar.

I'm using a 3840x2160 display, so to keep the pixels crisp I set the WinUAE "Display->Screen->Fullscreen" setting to 3840x2160 and the Amiga ScreenMode to 1920x1080, resulting in 2x2 physical pixels for each "Amiga" pixel since WinUAE scales it up to 3840x2160.

The same happens with RTG set to either "Full-window" or "Fullscreen". Of course in windowed mode it doesn't happen as no scaling takes place.

I don't know if it could be an issue with D3D itself, or the buffer used by WinUAE, but the WinUAE window (F12) doesn't show any artifact in fullscreen mode even though the GUI too gets scaled up.

With DirectDraw there are no scaling artifacts but for some reason the boot time seems much longer, and the gfx speed is around 10% slower overall, according to the intuition and graphics tests of SysSpeed.

I'd call these artifacts a minor issue as the rest of the screen is razor sharp :-)

Ironically Windows doesn't know how to set a proper 2:1 ratios for itself and gets all blurry if trying to set the desktop resolution to 1920x1080.

[Toni Wilen]

You need to confirm it with OS3 and also if it happens with some smaller resolution. (for example 1680 or 1440 wide)

[AlexC]

I can certainly try with OS3, as for the other resolutions I'm not sure the artifacts would be visible since the screen will be blurry again as the scaling won't have a perfect 2:1 ratio.

[Toni Wilen]

Originally Posted by AlexC

I can certainly try with OS3, as for the other resolutions I'm not sure the artifacts would be visible since the screen will be blurry again as the scaling won't have a perfect 2:1 ratio.

Windowed mode in same resolution should work exact same as fullscreen in monitor's native mode. (No 4k monitor until there are at least 100Hz capable ones = can't test)

[AlexC]

Ok, I tested with 3.1 and the same issue exists there too with 1920x1080.

At 1680x1050 in windowed mode it doesn't scale so the vertical lines look fine as the pixels are 1:1 but it's too small to use, and in full window it scales from 1680 to 3840 just like it does in fullscreen mode so there are scaling artifacts across the whole screen.

You might be able to reproduce the artifact without a 4K monitor. My guess is that if you can open a screen (e.g. with picasso96mode test screen) at exactly half the physical resolution of your monitor, assuming your Windows desktop is set to the physical resolution, you'd have a 2:1 ratio as well, showing the artifacts.

[Toni Wilen]

I want confirmed test case, sorry. There is chance it is windows/driver/hardware/something specific and I am not going to hunt for something that does not happen.

[Toni Wilen]

Does it happen if you select smaller resolution, tick "always scale in window" (rtg panel) and then type resolution*2 to display panel width and height boxes?

[AlexC]

Ok, I tried it that way with a 1366x768 resolution in a 2732x1536 window.

A similar vertical strip of unevenly stretched pixels happens, over fewer pixels but still roughly a 1/16th ratio of the screen width.