Anti aliasing

[NotMyFault]

Hi, 

i tried to understand how anti aliasing works on iPad (view mode is fixed to bilinear).

I start with a rectangle of 10px width, then stretch it to about 20px, and rotate it.

what really surprises me it how resampling / anti aliasing works on the edges.

• as long you only rotate, you get a nice expected AA of about 2px width around the edge
• if you stretch to 20px (factor 2), but play a bit around the exact number, it becomes really strange. One side gets smoothed over 4-6px, but only when below 20px. Above 20px, AA almost stops working.
• The other edge has its own impact.

To summarize, i could not find a clear explanation why and when the edge AA kicks in, and at what scale (1px, larger that 1px).

The video shows the alpha channel only (via channels panel).

 

[NotMyFault]

No AA above 20px

Strong AA/smoothing below 20px

[NotMyFault]

Maybe an explanation: once you stretch layer dpi above 200%, AA calculation gets wrong. As the pixels in the bitmap layer might get too far away from the edge of the canvas pixels, Affinity forgets to include them.

Looking at the file with Designer helps to spot the issue, when you activate vector and pixel view in parallel.

I filled the 10x10px rectangle with a checkered board, this time you see all channels normally.

A levels adjustment was used to boost all nonzero alpha to 100%.

You can see that the canvas pixel directly right to the vector/pixel slider is fully transparent. This is a bug. It should be partiality  transparent about 10%, according to the small share intersecting with the bitmap layer.

rect res aa issue.afdesign