Search found 281 matches

by ingenious
Sat Apr 27, 2019 10:40 pm
Forum: General Development
Topic: Point lights and non-diffuse brdfs
Replies: 9
Views: 477

Re: Point lights and non-diffuse brdfs

I mostly agree with you, vchizhov . My understanding is that the delta function is an ad-hoc construct, often defined as \int_{-\infty}^\infty f(x) \delta(x - x_0) \, dx = f(x_0) Note that the above is not a valid Lebesgue integral. A more rigorous, Lebesgue-compatible definition is as a measure: \i...
by ingenious
Thu Apr 25, 2019 5:34 pm
Forum: General Development
Topic: Point lights and non-diffuse brdfs
Replies: 9
Views: 477

Re: Point lights and non-diffuse brdfs

Point and directional light sources are not physical and are commonly defined via delta functions/distributions. For a delta directional light, you take the solid angle version of the rendering integration (which is what you have above) and replace L_i by a an angular delta function, which makes the...
by ingenious
Thu Jul 26, 2018 11:12 am
Forum: General Development
Topic: Emissive surfaces and visibility term
Replies: 6
Views: 2612

Re: Emissive surfaces and visibility term

In Veach's framework the measurement contribution of a path is always the same and it includes all cosines and inverse squared distances along the entire path. But a given path can be sampled in many different ways, i.e. via different techniques. The pdfs of some techniques will include some cosines...
by ingenious
Thu Jul 26, 2018 11:01 am
Forum: ompf2
Topic: Something's wrong with the RSS and forum posting
Replies: 3
Views: 9611

Re: Something's wrong with the RSS and forum posting

Everything seems to be back to normal, thanks a lot Jacco!
by ingenious
Tue Jul 24, 2018 4:43 pm
Forum: ompf2
Topic: Something's wrong with the RSS and forum posting
Replies: 3
Views: 9611

Something's wrong with the RSS and forum posting

I now always get a message "No route found for "GET /ompf2/viewtopic.php" when posting in the forum or when opening a topic from the RSS feed. Any ideas?
by ingenious
Tue Jul 24, 2018 4:41 pm
Forum: Links & Papers
Topic: Primary Sample Space Path Guiding
Replies: 3
Views: 1819

Re: Primary Sample Space Path Guiding

I was initially excited by the title of the paper but I soon found a deal-breaker. With primary-/path-space path guiding, the dimensionality of the ideal cache is infinite. But the radiance field in the scene in world space is only a 4D or max 5D function (surface/volume + direction). Prior path gui...
by ingenious
Tue Jul 24, 2018 4:36 pm
Forum: General Development
Topic: Emissive surfaces and visibility term
Replies: 6
Views: 2612

Re: Emissive surfaces and visibility term

TL;DR: If a ray randomly hits a light source, you should not be multiplying by the cosine as it's importance sampled and cancels out. In Veach's integral formulation of light transport it's all crystal clear. The radiance emission at every point on a diffuse light source is uniform (i.e. the same in...
by ingenious
Thu Mar 01, 2018 1:48 am
Forum: Visuals
Topic: My little path tracer
Replies: 28
Views: 12641

Re: My little path tracer

Will investigate. Hints appreciated ;-) Yeah, doesn't look correct. The most likely reason is that the MIS weights corresponding to the different techniques for constructing a path don't sum up to one. This in turn is probably due to incorrect/inconsistent path pdf computation. What has helped me g...
by ingenious
Tue Jul 11, 2017 4:30 pm
Forum: General Development
Topic: MIS with IBL
Replies: 14
Views: 12125

Re: MIS with IBL

The problem is that the probability you use for choosing a light source is itself a random variable. If you write out the estimator you're building with your sampling techniques, its expected value won't be what you want. To get an unbiased estimator, you'll need to divide not by that random probabi...
by ingenious
Mon Apr 17, 2017 4:58 pm
Forum: Tools, Demos & Sources
Topic: Implementation for Blue-noise Dithered Sampling
Replies: 26
Views: 20322

Re: Implementation for Blue-noise Dithered Sampling

The idea ideas not adding a deterministic (blue-noise) number to a random number. In fact, the idea is to get rid of the randomness altogether - you use the deterministic number to post your pattern, instead of using a random number. Regarding the (0, 0.99) vs (0, 0.01) issue, the answer is that it ...