Search found 21 matches

by dawelter
Tue Apr 24, 2018 8:49 pm
Forum: Visuals
Topic: My little path tracer
Replies: 14
Views: 4410

Re: My little path tracer

I haven't had implemented a refractive material till now. That needed to be rectified badly.

RefractiveCaustics.jpg
RefractiveCaustics.jpg (244.13 KiB) Viewed 554 times

Not too shabby, I suppose.

(Although, since SDS paths are not rendered, parts are missing. I.e. in lower row, areas behind the glass. And top right, the beam behind the glass.)
by dawelter
Mon Apr 23, 2018 6:33 am
Forum: General Development
Topic: Veach - refractive BTDF adjoint
Replies: 0
Views: 461

Veach - refractive BTDF adjoint

Hello! I'm trying to understand Veach's derivation of the adjoint of the specular refractive BTDF. It seems I hit a brick wall. Some of that stuff looks like black magic to me. Specifically, there is a relation for differential solid angle on the following page: non-symmetry-due-to-refraction.png Wh...
by dawelter
Fri Apr 20, 2018 7:44 am
Forum: Visuals
Topic: My little path tracer
Replies: 14
Views: 4410

Re: My little path tracer

Thank you beason! Actually there was a bug. I wrongly assumed that pdfs for BSDF sampling are symmetric which they are clearly not. p(wi,wo) = p(wo,wi)? No! no! Ah well, how does one say, assumptions are the mother of all f'ups. I finally realized my mistake when ... I implemented statistical tests ...
by dawelter
Sat Mar 24, 2018 8:38 am
Forum: Visuals
Topic: My little path tracer
Replies: 14
Views: 4410

Re: My little path tracer

I threw a "real world" scene at it. Thinking about how else I could exploit volume caustics in lack of refractive materials, I figure it would be cool to build a solar thermal power plant model. :-D Modelled in Stud.io and Cinema 4D. 677761 Triangles, most of them occluded due to the brick...
by dawelter
Wed Mar 21, 2018 1:26 pm
Forum: General Development
Topic: Spectral tracking question
Replies: 6
Views: 1097

Re: Spectral tracking question

Cool! And thanks for the link to the paper. Very interesting. Do you think it is possible to modify closed-form tracking in such a way that it handles spectrally refined absorption/scattering for homogeneous media correctly? For homogeneous media you have the analytic expression for the transmittanc...
by dawelter
Mon Mar 19, 2018 8:25 am
Forum: General Development
Topic: Spectral tracking question
Replies: 6
Views: 1097

Re: Spectral tracking question

Do you think this looks reasonable? Not sure. The method is pretty noisy, indeed. I actually wonder how you get your reference image so clear with jut 16 spp. Try the weighting scheme from "5.1.2 Incorporating Path History". It should reduce the noise somewhat. I spot one error: - t is up...
by dawelter
Sat Mar 17, 2018 3:09 pm
Forum: General Development
Topic: Spectral tracking question
Replies: 6
Views: 1097

Re: Spectral tracking question

Hi, 1. The data is homogeneous, so null collisions don't play a role at the moment I think this is incorrect w.r.t. spectral tracking. Because mu^bar = max_lambda { mu_t(lambda) }, you get mu_n = mu^bar - mu_t > 0 for some lambda if not all mu_t(lambda) are equal. Moreover, the weights are multiplie...
by dawelter
Fri Mar 16, 2018 8:34 am
Forum: Visuals
Topic: My little path tracer
Replies: 14
Views: 4410

Re: My little path tracer

I think I squashed the worst bugs. This is fun stuff.
parabolic_reflector_volumetric.jpg
parabolic_reflector_volumetric.jpg (477.89 KiB) Viewed 1143 times

A perfectly parallel beam send through a scattering medium. The sphere is made of a much denser medium. It is sub surface scattering with brute force BDPT.
boxy_laser.jpg
boxy_laser.jpg (428.54 KiB) Viewed 1143 times
by dawelter
Fri Mar 16, 2018 8:27 am
Forum: General Development
Topic: Geometry factor for parallel light?
Replies: 2
Views: 891

Re: Geometry factor for parallel light?

Yeah, I wasn't clear. I was mostly thinking of the path densities used to compute MIS weights. Eq 10.9 in Veach's thesis. So this is really a question about the density of the end points in the left hand side case. I suppose the density does not change no matter how much I would move the target surf...
by dawelter
Sat Mar 03, 2018 9:48 am
Forum: General Development
Topic: Geometry factor for parallel light?
Replies: 2
Views: 891

Geometry factor for parallel light?

Say we have a source of parallel light, described by a delta distribution like Le(x,w) = dirac_delta(w-w0)*f(x). This could be a "laser-like" source like I indicated in the pic below or an infinitely distant light. parallel_light_handling.png Question is, when to add the 1/r^2 factor in th...

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