Search found 138 matches

by shiqiu1105
Wed Jan 15, 2014 2:35 am
Forum: General Development
Topic: Anybody tried implementing Disney's Principled BRDF?
Replies: 11
Views: 12485

Re: Anybody tried implementing Disney's Principled BRDF?

1. I guessed that the 2 specular lobes are two seperate brdf weighted by Fresnel. But in each of the brdf, there are already a Fresnel term in the microfacet model. How exactly are they combined? Whatever energy is not reflected by the coating BRDF goes through to the base BRDF. Since the energy re...
by shiqiu1105
Mon Jan 13, 2014 10:05 am
Forum: General Development
Topic: Anybody tried implementing Disney's Principled BRDF?
Replies: 11
Views: 12485

Re: Anybody tried implementing Disney's Principled BRDF?

Their principled BRDF is based on Walter et al. "Microfacet Models for Refraction through Rough Surfaces" GGX BRDF. I'd recommend reading this article. You can find an implementation of the GGX BRDF in Disney's "BRDF Explorer": an open source application for exploring the characteristics of BRDFs. ...
by shiqiu1105
Sun Jan 12, 2014 3:09 am
Forum: General Development
Topic: Anybody tried implementing Disney's Principled BRDF?
Replies: 11
Views: 12485

Anybody tried implementing Disney's Principled BRDF?

Hi all, I have been reading the note from Disney about their principled BRDF. http://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf And I just don't think this note has provided enough detail for others to implement it. In particular, I don't understand how their specul...
by shiqiu1105
Fri Dec 06, 2013 3:47 am
Forum: General Development
Topic: How to do depth of field in Light tracing?
Replies: 3
Views: 4262

How to do depth of field in Light tracing?

I am trying to implement depth of field in my bidirectional path tracer. I know how to do that when tracing rays from the camera. But when connecting light path directly to camera, that's like light tracing, where points are projected back directly to pixel positions. So I tried to purturb the proje...
by shiqiu1105
Sun Nov 17, 2013 4:07 am
Forum: General Development
Topic: About volumetric caustics.
Replies: 23
Views: 19043

Re: About volumetric caustics.

On this scene neither VCM nor Metropolis will help. I suggest caching illumination in some data structure and then do distribution ray tracing at the first bounce from the camera to query this structure. That is, using something like VRay's light cache. Irradiance caching is also great for this sce...
by shiqiu1105
Sun Nov 17, 2013 1:05 am
Forum: General Development
Topic: About volumetric caustics.
Replies: 23
Views: 19043

Re: About volumetric caustics.

On this scene neither VCM nor Metropolis will help. I suggest caching illumination in some data structure and then do distribution ray tracing at the first bounce from the camera to query this structure. That is, using something like VRay's light cache. Irradiance caching is also great for this sce...
by shiqiu1105
Sat Nov 16, 2013 10:17 pm
Forum: General Development
Topic: About volumetric caustics.
Replies: 23
Views: 19043

Re: About volumetric caustics.

Does make sense to compare VCM and a Metropolis Sampler ? I mean, aren't they orthogonal and solve different kind of problems ? I use BPT+VCM with a Metropolis Sampler; there is nothing preventing to use both. Anyway a Path racer with a Metropolis Sampler have no hope to render any no trivial SDS p...
by shiqiu1105
Sat Nov 16, 2013 5:58 am
Forum: General Development
Topic: About volumetric caustics.
Replies: 23
Views: 19043

Re: About volumetric caustics.

Now that we are discussing this, I am curious that if MLT like algorithm is so robust, why do we still care about algorithm like VCM?
Can MLT handle SDS path efficiently?
by shiqiu1105
Fri Nov 15, 2013 6:41 am
Forum: General Development
Topic: About volumetric caustics.
Replies: 23
Views: 19043

Re: About volumetric caustics.

Anyway, I guess the take home msg for volumetric caustics is I need to at least do a Metropolis sampled BDPT right?

And, besides sampling methods, I am also quite unsure about how to implement multiple scattering with BDPT or PT either. Any recommended tutorial?
by shiqiu1105
Thu Nov 14, 2013 8:32 pm
Forum: General Development
Topic: About volumetric caustics.
Replies: 23
Views: 19043

Re: About volumetric caustics.

What mumbo-jumbo is that? Kelemen-style MLT doesn't require much. You need to to feed sample results back to the random number generator, and let the thing warm up a bit to generate an average intensity and eliminate start-up bias. Otherwise it's not really any more complicated than, say, replacing...