Stretch and Tilt

[pwwit1]

Hello,

 

I'm having difficulty understanding how sprite stretching works.

 

In the image below, these 4 sprites (Sizes: 40x40, 32x32, 16x16 and 1x1) have exactly the same tilt and stretch values, but the amount of stretch varies by the sprite size.

I've noticed that the stretch value seems to be multiples of the sprite width, which is fine for 1x1 sprites as the stretch and tilt are equivalent at this size. This is a problem because the larger the image the less precision the stretch attribute has.

 

It also seems to contradict the documentation, which says stretch is a 16-bit fixed point value that is added to HSIZE per scanline (Although it does say per 'unit size', maybe 'unit size' is the sprite width?)

With 8-bits of precision I should be able to increment the stretch 1/256th of a pixel per scanline, but it seems to increment 1/256th * Sprite Width per scanline.

 

Is this correct behavior, if so, is it possible to create arbitrary polygons with large sprites?