2d polygon(,,,,) function does not render the lowest row of pixels.

I'm using allegro 4.1 and devc++.

I don't know about this specific case, but please note that almost all graphics libraries on purpose do not draw the left-most or right-most or whatever-most pixel of a polygon, because if you paste together polygons you want to be able to prevent any overdraw (which becomes extremely critical if the polys are transparent -- if you drew all pixels you would see 1 pixel lines at the poly borders).

polygon3d_f draws neither the right nor the bottom pixels.

So probably, since triangle and polygon draw the right pixels, they should draw the bottom pixels as well.

Do you have a patch to correct this? If not, I'll have a look at polygon.c.

I see no need. You use polygon if you don't want them skipped, polygon3d otherwise.

I also seem to remember something, but a search revealed nothing. Anyway, there's no reason to make it not either skip the right pixels, or draw the bottom ones. And seeing how we have line, rectangle, triangle, polygon all together in the docs, they should all behave the same (so draw the right and bottom pixels).

Ah, yes, that explains it.. must have read one of those threads on the forums. Nothing ever went through to [AD] though. I'll make a patch later to fix it (well, assuming, it is a quite simple case of changing a y < height to y <= height in a for loop).

Ah, great. I wonder how that was missed.. someone really should have forwarded it to [AD] when no devs noticed it. Luckily I didn't get around yet to look at it, so now can just create a patch from Surt's code Thanks for finding it!

[that is, i had the same avatar since years.. me looks puzzled]

[Edit:]
Hm, the patch by Surt doesn't work.. it overdraws parts of the polygon, which is not acceptable.

[Edit2:]
Seems hard to fix. The polygon renderer constructs a list of edges, sorts them, then draws them line by line from above. It always skips the last line, in order not to overlap with the next edge below an edge.
Of course, this breaks everytime a lowest edge is reached. (E.g. in a W shape, it forgets the 2 bottom pixels, or in a box shape, the entire bottom line.) I don't see how an algorithm for this would work.. anyone has experience with writing software polygon renderers?

They are sorted as far as I see. So yeah, they could be done as a separate pass. Maybe it's the best. So, it would mean, walking the polygon edges, detecting minima, and figuring out the length of a hfill to draw at every such minimum.

There can be multiple last scanlines (e.g. an M shaped polygon has 3 minima), so it's not completely easy. It's easy enough once the algorithm used is understood, I guess.

Yes, I like the idea as well.. it gets one step closer to OpenGL polygons But anyway, maybe we should think about making polygon a simple wrapper around polygon3d, and add the possibility for borders to that. It doesn't look like anyone is up to fixing the code in polygon.c anyway.

Now if it's easier to add optional right and bottom edges to the polygon3d code, I have no idea..

For example, I often use rectangle.