pouët.net

Watching Frameranger, I am reminded of a rendering artifact that I'm hoping someone can explain to me. The artifact shows up as slightly perturbed (dithered?) noise in shaded areas, but what is interesting is that the noise "pattern" stays the same, and grows lighter or darker based on what the light source and/or object is doing. If it were simple random or FS-dithered noise I would expect the noise pattern to be constantly changing -- it isn't. (I kind-of like this artifact, as it is friendlier to video compression algorithms :-) So what is this? Is it a quick'n'dirty way to do ambient occlusion or something?

I am starting to see this all over; most recently in Frameranger (the low-res relief middle part) and I first noticed it in Into The Pink (the marbled ball scene middle part).

Any ideas? Did I describe it properly? Do I need to provide a video clip as an example?

we used noise in a large number of places in fr. it's a nice way to dither away potential artefacts and banding when we have to undersample (realtime, you know).
could be one or more of the following:
- the dof uses a noise pattern
- the raycasting on the realtime ao uses a noise pattern to offset the rays, reducing the artefacts from not enough rays (realtime..)
- the raytraced volumetric lighting on the car headlights uses a noise pattern to dither the ray march's start position, to dither the sampling/potential banding
- the edge aa post fx (that we use to compensate in some places for lack of aa with deferred on dx9) uses a noise pattern
- some of the shadow sampling uses a noise pattern
- the 3d fluid renderer (for smoke only) uses noise for a bit of dither

usually the noise is based on screen or world position so it doesnt move between frames. maybe a screenshot of which part would help identify the reason.

oh, you said "the low-res relief middle part" - that would make it the ao raycaster that's causing it. :) its an easy way to fix the lack of rays.

for high-tech :)

"If you didn't see it, that means it's working"

gloom: exactly!

but I *did* see it ;-) But still mad props because of the skill required.

Thanks for the smash perspective, btw. Hopefully someone from plastic can comment.

In 2009 I'm still reeling from the fact that many effects are shaders. We need a GFX/OS so that the host OS isn't even necessary (although how you would get audio out of a video card is an exercise best left to humor).

I demand a Bayer dither pattern next time, for a tiny oldskool signature. ;)

I find your lack of rays disturbing

here's a couple more rays for you, smash:

... as opposed to getting video synch out of an audio card. That's fucking ridiculous.

There was a way to get AM-radio tunes out of a CRT by displaying coded patterns... so the shader-based GFX/OS would have to be restricted to run on CRT monitors or old TVs.

GRAFENWALDER

god that stuff has given me a headache once.. (GRAFENWALDER STRONG)

I actually did a DOF shader using dither instead of blur... I just called it art.

:)

so there's Grafenwalder and Grafenwalder Strong? It's like piss and superpiss!