Chrome problem with the Beta

[Mandrake]

I'm thinking this might be better off in moodflow's shadow thread as it may be related, not sure.
I have 3 different chrome settings here, all of them worked ok on the last build.
It seems that in some places the render engine just passed over the prepass and then there are all the black artifacts.
I'd have to guess this is a reflection issue though, so I started this thread.

Not sure of the build I used on the Chevy, I know it has issues, please disregard them as this was a test.

[dandelO]

Because they're so shiny I'd assume this was an antialiasing issue. See this thread, particularly Oshyan's AA test images using sharp filters... http://forums.planetside.co.uk/index.php?topic=5142.msg53401#msg53401 and the following response from Matt about the black items on the really bright highlights... http://forums.planetside.co.uk/index.php?topic=5142.msg53401#msg53401

Looks like a similar thing to me.

[Mandrake]

This must be the response your referring to:

The catmull-rom and mitchell-netravali filters have "negative lobes" which have a slight sharpening effect. Unfortunately when you're sharpening high dynamic range images you have this problem of very bright pixels having very dark edges. When anti-aliasing bloom is on, Terragen changes the filter for bright pixels, avoiding this problem.


I'll play some more thanks!!

[Mandrake]

No Joy, box seems to be the calmest, but nothing seems to remove the black artifacts.

[cyphyr]

This was an issue with the build before last, got sorted with the last build (1.9.99.1). I think it was inked to the soft shadow but I may be wrong. Hope PS can sort this.
Richard

[Kevin F]

Here's a quick low res version of a scene originally done in the previous version.
This beta version seems to be fine as far as I can tell.
settings:
detail .6
aa 4
narrow cubic
no detail jittering

reflective shader set to 10 at quality 32

what are your reflective settings?

[Mandrake]

Kevin, that low res render is not fine, if you look close you can see black artifacts everywhere.

[Kevin F]

o.k. here's the original reduced to 400x300 but at higher resolution. does this have the problem?
if not, show me where on the beta version the artifacts are compared to this, and I'll re-render it at the same higher res.

[Mandrake]

Yes, it looks like you may have black lines running around where the edges meet.
Thanks for the effort though, I'll try your settings when i get a chance.

Plus your in very low light, bring the Sun up and see how it looks.

[Matt]

What are your reflectivity settings? Reflectivity values greater than 1 can be used but they're not physically plausible - i.e. could not happen in nature - and can give negative pixel values. To explain why, imagine you have an object which would normally render as white when there are no reflections. If it is reflecting something that is darker than itself, the colour of the object after accounting for reflection will be somewhere between the original colour and the colour of the reflected object. The mix of colours depends on the reflectivity of the surface and the angles of reflection. If your reflectivity is greater than 1, the pixel value will go beyond the colour of the reflected object, and that might push it darker than black.

I'm only guessing, but I suspect there are darker-than-black (negative) pixels here, and there could possibly be a new bug in the handling of negative pixels in the latest build. In older builds these negative pixels should render OK (they appear as black) but since I was working on the anti-aliasing routines it's quite probable that negative pixels aren't being handled correctly now. I will run some tests.

Matt

[Mandrake]

I was using black and a reflection shader of 10

[Matt]

I just wanted to add that if you're wanting the car to look realistic in a variety of environments, you should never set the reflectivity beyond 1. Index of refraction is OK with higher values, so try increasing that if you want a good amount of reflectivity at any angle. If your reflections still aren't as bright as you want, then whatever it is reflecting (e.g. the environment) needs to be brighter. (Or increase camera exposure.) But if photorealism is not your thing, disregard

Matt

[Matt]

I was using black and a reflection shader of 10

Hmm.. my initial thought was that black should be OK, because the reflections will only ever be brighter than that. I'm trying to think if multiple reflections could generate negative pixels though. I don't think they could. Hmm...

[Kevin F]

I just wanted to add that if you're wanting the car to look realistic in a variety of environments, you should never set the reflectivity beyond 1. Index of refraction is OK with higher values, so try increasing that if you want a good amount of reflectivity at any angle. If your reflections still aren't as bright as you want, then whatever it is reflecting (e.g. the environment) needs to be brighter. (Or increase camera exposure.) But if photorealism is not your thing, disregard

Matt

Matt, How would you recommend replicating chrome then? values of 1 for reflectivity just don't look realistic yet higher (silly) values do.

[Mandrake]

He just told you Kevin. Haven't ried this in a while. Mr. Lampost seemed to like this better also.

"1. Index of refraction is OK with higher values, so try increasing that if you want a good amount of reflectivity at any angle. "