I'm still looking for some definitive info or documentation, but it looks
like the issue is that it's using 24.8 fixed point to interpolate between
the pixels.
There's some interesting links below regarding this stuff. One workaround
seems to be to do the bilinear interpolation in the shader yourself, doing
4 pixel reads instead of 1. This does make it nice and smooth and is what
i'm doing in the image on the right
Another workaround I've found is to do two pixel reads, to have it either
do only the x interpolation or only the y interpolation in the hardware,
then do the other axis interpolation in the shader. This isn't as high
quality as doing the bilinear interpolation completely in the shader, but
it is only 2 texture reads instead of 4 and in my experiments is a lot
closer to the "software bilinear" than the "hardware bilinear" so seems
like a good win.
http://iquilezles.org/www/articles/hwinterpolation/hwinterpolation.htm
http://iquilezles.org/www/articles/texture/texture.htm
On Thu, Jun 4, 2015 at 2:10 PM, Alan Wolfe <alan.wolfe@xxxxxxxxx> wrote:
In this case, it's been super difficult to find any info because...
1) Not many people really do WebGL, which makes it hard to find WebGL info
out there specifically.
2) My usage case of wanting to bilinear interpolate data i've stored in
textures really doesn't seem to be common at all, which makes it hard to
find info about this topic - in any API - hard to find info on.
If I don't hear of anything and can't find anything, i'm going to try it
in DX and OpenGL and see if they have the same precision problems :P
On Thu, Jun 4, 2015 at 1:55 PM, Vince <dmarc-noreply@xxxxxxxxxxxxx> wrote:
Firstly, I'm thrilled to see some action here again.
I have not done much raw work in WebGL, but if I was looking for
state-of-the-art examples, I would check out three.js.
Vince~
------------------------------
*From:* Alan Wolfe <alan.wolfe@xxxxxxxxx>
*To:* gameprogrammer@xxxxxxxxxxxxx
*Sent:* Thursday, June 4, 2015 3:21 PM
*Subject:* [gameprogrammer] WebGL has low quality bilinear filtering?
Anyone out there do any webgl? might be a generic gfx question though...
Check this out:
http://demofox.org/BilinearTest/bilineartest.html
The left side uses the built in bilinear filtering and has obvious noise
/ non smoothness in the interpolation.
The right side grabs the four pixels and does the bilinear interpolation
in the shader, which makes for nice smooth interpolation.
No matter i try, i cannot seem to make the built in interpolation higher
quality. I've tried a few different machines and all major browsers, all
has the same results.
Does anyone know if this is a solvable issue? or is it what we live with,
with current hardware?
Thanks!!
