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by szellmann
Wed Jul 25, 2018 7:59 pm
Forum: General Development
Topic: Emissive surfaces and visibility term
Replies: 6
Views: 584

Re: Emissive surfaces and visibility term

@ingenious Thanks, that was helpful! I read Veach's thesis Chapter 8 which explains a lot. The intensity of the emissive objects themselves is uniform (i.e. same intensity in every direction), as you sad. When I just naively evaluate the LTE, cosine terms etc. come into play inside the integral. Whe...
by szellmann
Tue Jul 24, 2018 8:39 am
Forum: General Development
Topic: Emissive surfaces and visibility term
Replies: 6
Views: 584

Re: Emissive surfaces and visibility term

all geometric factors relating to the light source--surface area, distance, and cosine term--are accounted for in the probability of a ray hitting the light source "by accident." This explanation makes sense. What confuses me however is that both surface area and distance (squared) are pa...
by szellmann
Sun Jul 22, 2018 9:48 pm
Forum: General Development
Topic: Emissive surfaces and visibility term
Replies: 6
Views: 584

Emissive surfaces and visibility term

I'm wondering, in a naive path tracer w/o NEE or MIS, do I have to scale the contribution of an emissive surface by a dot(n, -ray.dir) term? Intuition says yes because light intensity depends on solid angle - lights viewed from a grazing angle appear darker than lights viewed from normal direction. ...
by szellmann
Thu Mar 22, 2018 12:05 pm
Forum: General Development
Topic: DXR
Replies: 6
Views: 2080

Re: DXR

Here: https://www.youtube.com/watch?v=yaK1e59-oAA it suggests that RT is currently a software feature, but that future GPUs will have fixed-function hardware. ("..the next generation of AMD and Nvidia will have hardware to speed this up.."). This is the most important takeaway IMO.
by szellmann
Mon Dec 04, 2017 10:54 pm
Forum: General Development
Topic: Why is volumetric emission proportional to absorption coefficient?
Replies: 5
Views: 2821

Re: Why is volumetric emission proportional to absorption coefficient?

I think it is required that emitting particles should not scatter light I'm not quite sure if I understand how you come to this assumption and if I totally understand your question, but I don't see why particles that emit light shouldn't also scatter light. However, the mental model behind radiance...
by szellmann
Tue Nov 28, 2017 9:17 pm
Forum: General Development
Topic: Why is volumetric emission proportional to absorption coefficient?
Replies: 5
Views: 2821

Re: Why is volumetric emission proportional to absorption coefficient?

I don't quite understand the question: doesn't the first term refer to a particle density at an integration position x that emits radiance L_e in viewing direction w, and that the particle density absorbs radiance by w.r.t. sigma_a(x)? The emitted radiance is not proportional to the absorption, but ...
by szellmann
Wed Jun 21, 2017 1:48 pm
Forum: Tools, Demos & Sources
Topic: Visionaray Ray Tracing Framework
Replies: 11
Views: 22982

Re: Visionaray Ray Tracing Framework

Here's the (extended) AO results from the SEARIS paper (https://szellmann.github.io), along with a script to run the benchmark. Results for interesting platforms (CPU,GPU) not listed yet are highly welcome!
by szellmann
Thu Mar 16, 2017 10:40 am
Forum: Tools, Demos & Sources
Topic: Visionaray Ray Tracing Framework
Replies: 11
Views: 22982

Re: Visionaray Ray Tracing Framework

Going to talk about Visionaray at SEARIS (http://www.searis.net), which is a workshop colocated with IEEE VR.

Check out this teaser video: https://youtu.be/bhhwEO4KWII
by szellmann
Fri Jan 20, 2017 9:10 pm
Forum: General Development
Topic: Intersection of ray with quadric surface for hobby ray tracer
Replies: 6
Views: 5102

Re: Intersection of ray with quadric surface for hobby ray tracer

Here's an explanation of how to build up the 4x4 matrix for several quadric types: https://www.siggraph.org/education/materials/HyperGraph/raytrace/rtinter4.htm I believe that Glassner's 1980's book "Introduction to Ray Tracing" also has a paragraph on this. There's a ray/quadric implement...

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