[motherhamster] SVN: james/243 Display dirt using a png sprite.

[Brian Fisher]

On 4/11/07, Bob the Hamster <Bob at hamsterrepublic.com> wrote:
> Is that the blend_mode member of the ImageAsset? I tried all three of
> alpha_blend, additive, and lighting. That isn't it, is it?
>
No, I don't have the code in front of my, but there is some opengl
call that is like "polygon_smooth" or something like that - if set to
true, it antialiases edges, which can mess up tiling if things don't
tile exactly on pixel boundries

It's a tradeoff thing - if your art goes all the way to the edge, and
you are either always tiling on pixel boundries, or you never tile,
the antiliasing can be nice.

If you are tiling on non-pixel boundries, and all non-tiling art
doesn't go all the way to the edge, then antialiasing is a bad thing

...another possible cause of something like this could be when art is
scaled, and the video card filters the edges dumbly (it may filter a
colored opaque pixel with a transparent black one and get a half-black
half-transparent pixel, instead of getting a full colored
half-transparent pixel) but if you can fix things by increasing the
scale or overlapping a bit, then this is definitely not the problem.

Finally, careful tiling with unscaled art that is well positioned on
pixel boundaries is good in all cases, so maybe I just have some
sloppy positioning code...


> By the way, lighting sounds interesting. How is it intended to be used?
>
The alpha of each source pixel will say how much of the destination
pixel color is retained, while the rgb color of the source pixel says
how much of the rgb of the destination pixel color should be added in.
It's only interesting when it's rendered on top of existing stuff

So like say you have some image that is fully opaque black, with an
opaque red fuzzy circle in the middle. The fully opaque black means
leave the pixels alone, while the opaque red means leave the existing
color (opaque) but add in some multiple of the red. So if you render
that with lighting blend, it would be like a red spotlight being shone
- where red things pick up the red light.

Now say you've got some image that is fully transparent black, with an
opaque black circle in the center. Where it is fully transparent
black, it means remove all the original color and add nothing in (like
fully shadowed). Where it is opaque black, it means retain some
percentage of the original color (based on the alpha) and add nothing
back in (the black). So it's basically like turning off the lights,
but leaving a white spotlight on.

Makes sense?