Search found 11 matches

by Chaos
Fri Aug 08, 2014 3:04 pm
Forum: General Development
Topic: Color space: when to multiply by the matrix
Replies: 13
Views: 9026

Re: Color space: when to multiply by the matrix

Hi, Thanks everyone for your insights, all interesting comments! To add some context, one of the reason people are trying to render 'with the color space X', instead of converting all colors to a more standard (CIE) RGB space is because of 'plates'. Basically, a client would give you a backplate in ...
by Chaos
Wed Jun 11, 2014 11:35 am
Forum: General Development
Topic: Color space: when to multiply by the matrix
Replies: 13
Views: 9026

Re: Color space: when to multiply by the matrix

First of all: As long as you render RGB your results will be wrong (except of some special cases). In order to do anything real you need to use spectral rendering, otherwise the metamerism will take care of everything being just wrong. I totally agree here of course, but I'm not sure VFX companies ...
by Chaos
Mon Jun 09, 2014 1:19 pm
Forum: General Development
Topic: Color space: when to multiply by the matrix
Replies: 13
Views: 9026

Re: Color space: when to multiply by the matrix

Thanks Mohamed! This is also something I've seen happening somewhere else. It still feels weird though, since usually when working with different unit systems, things cancel out or contains squared dimensions. There is probably still something I don't understand, because I'm disturbed by the fact co...
by Chaos
Wed Jun 04, 2014 9:22 pm
Forum: General Development
Topic: Color space: when to multiply by the matrix
Replies: 13
Views: 9026

Color space: when to multiply by the matrix

Hi, This topic may not be as technical or full of equations as the other ones, so please excuse me :) There is something I don't quite understand when using colour space transforms. Let's assume my renderer work in a given linear colour space called A. The renderer takes different kind of colour inp...
by Chaos
Fri Mar 28, 2014 7:25 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9592

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

I will have a look at this thread, thanks a lot for the insights :)

Cheers,
Jonathan
by Chaos
Fri Mar 28, 2014 7:23 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9592

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

I finally managed to get something working! The thing that slowed me down the most was naively inverting the eta based on the 'sidedness' of my view ray, while (as far as I understand) the paper actually relates eta to the normal orientation. This means that the paper's equation manage the special-c...
by Chaos
Fri Mar 28, 2014 9:54 am
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9592

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

Hi, This is indeed the paper I was using. There seem to be an error in equation (40), where they should use eta*eta inside the square root (since they are manipulating sine/cosine). I didn't find that mentioned anywhere :/ At the moment I'm stuck on 'why do they use sign(i.n) in this equation (40)'?...
by Chaos
Tue Mar 25, 2014 5:48 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9592

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

Hi, I have been working with prman RSL for some years now, so I know about these :) Sadly, there are many many many subtleties at all levels in prman, so generally the documentation will be lacking, if you're encountering a non-trivial issue. To be fair, plausible shading works nicely, but edge case...
by Chaos
Mon Mar 24, 2014 8:30 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9592

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

Hi, I'm still struggling to have my microfacets working together, but it may be that I'm too picky... One thing I was reluctant to do is generating zero-pdf directions from the equivalent to bsdf->sample() method, because in my mind, it didn't make sense to generate a direction with a zero pdf (if y...
by Chaos
Fri Mar 21, 2014 9:25 am
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9592

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

Ah I wasn't clear enough, sorry! I am aware that generally, the pdf and the bxdf response are different. I was asking about the pdf returned by generate() and the pdf returned by evaluate() (same for bsdf response). The way I understand it, if you were to generate a direction with generate() (gettin...