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Re: Painter bug? [message #31548 is a reply to message #31540]

Sat, 12 March 2011 22:14

Mindtraveller
Messages: 917
Registered: August 2007
Location: Russia, Moscow rgn.

Experienced Contributor

Thank you for the replies. The problem is clear now.
Currently I see the only solution, and I'm not really shure you want it. Smile

Anyway. We could use temporary surface which stores color + alpha for a sequence of operations. On writing a pixel, it's color is calculated in usual way, but alpha is added to the current alpha value. E.g. we will have alpha = 256 in previous Mirek's example. Rendering this temporary surface to actual image will give solid black color which is absolutely right result.
This could look like this:

painter
    .BeginComplex()
    ./*draw polygon 1*/
    ./*fill polygon 1*/
    ./*draw polygon 2*/
    ./*fill polygon 2*/
    ./*draw polygon 3*/
    ./*fill polygon 3*/
    .EndComplex()
;

UPDATE: OK, here is quick and dirty "back-end" solution. Let's imagine we draw polygons in scaled coordinates:
painter.Scale(scale);
To avoid polygon stitching you may simply move polygon adjacent vertices with 0.5/scale towards neighbouring polygon, i.e.
painter.Move(x[i]+.5/scale,y[i]);
It moves polygon vertex to the next physical pixel if it's position is actually between pixels.
This technique seems like eliminating visual artifacts with U++ rendering of adjacent polygons.

[Updated on: Sat, 12 March 2011 22:58]

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