## Search found 52 matches

Sat Mar 03, 2018 9:48 am
Forum: General Development
Topic: Geometry factor for parallel light?
Replies: 2
Views: 4773

### 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 the geometry...
Sat Mar 03, 2018 7:51 am
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### Re: My little path tracer

Thanks Ingenious. Indeed it was wrong MIS weighting. My logic for splatting on the light image is slightly odd and so it came that the weights for techniques with one eye vertex were much too low. Had to factor in the number of pixels. Got a clue by imaging MIS weights for various eye/light path len...
Wed Feb 28, 2018 8:43 am
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### Re: My little path tracer

Thank you graphicsMan! :-) Meanwhile, I implemented what I want to be mis weighting straight from the defnition p_k^a / sum_i p_i^a ... I also fixed the reflector. It has 10k triangles now and increased tesselation near the focal point. The light source was a point light, now I take very small spher...
Thu Feb 22, 2018 8:44 am
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### Re: My little path tracer

Bidirectional path tracing! The first correct image! Well, as far as I can tell
cornelbox5.jpg (351.36 KiB) Viewed 7905 times
High variance at 128 bidirectional random walks per pixel. Paths are weighted by one over the number of techniques that can generate the path. Implementation of MIS pending ...
Wed Feb 07, 2018 7:56 am
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### Re: My little path tracer

Thank you! Meanwhile I have a better pic. Something about the clouds strikes me as odd. Still a nice second try if you ask me. :-) atmosphere_cloudy.jpg To test my algorithms needed a material that has a "delta peak" plus a continuous density, so I implemented a dielectric material with a perfectly ...
Sat Jan 20, 2018 2:05 pm
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### Re: My little path tracer

Been working on my path tracer. Implemented table lookup for the height profile of collision coefficients. After some more work I could reproduce the blueness of the evening sky due to absorption by ozone. atmosphere_fisheye_ozone_compare.jpg Now there is support for area lights - in the form of tri...
Mon Dec 11, 2017 12:42 pm
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### Re: My little path tracer

Trying to reproduce results from Peter Kutz's Sky Render. Using 10 discrete wavelengths, no ozone, purely exponential density decrease. Something is wrong. Much too greenish for my taste. atmosphere_fisheye1.jpg atmosphere_fisheye2.jpg My approximation to the solar emission spectrum might be inadequ...
Sat Dec 09, 2017 9:30 am
Forum: General Development
Topic: Why is volumetric emission proportional to absorption coefficient?
Replies: 7
Views: 14637

### Re: Why is volumetric emission proportional to absorption coefficient?

I found an interesting lecture script. http://www.ita.uni-heidelberg.de/~dullemond/lectures/radtrans_2012/Chapter_3.pdf Section 3.3 Eq 3.9. As I understand, ultimately it is a matter of definition motivated by thermodynamics of a special case. I imagine that the same particles that block light along...
Sat Dec 09, 2017 8:39 am
Forum: Visuals, Tools, Demos & Sources
Topic: My little path tracer
Replies: 36
Views: 20070

### My little path tracer

This came out of my path tracer. cornelbox3.jpg Unfortunately convergence stagnated after some 10k samples per pixel. Not unexpected since it is a difficult scene. Lit by two point lights through the holes in the ceiling. I haven't implemented area lights. The medium has chromatic collision coeffici...
Sun Nov 26, 2017 10:44 am
Forum: General Development
Topic: Weighted delta tracking question
Replies: 4
Views: 6700

### Re: Weighted delta tracking question

Ah all right. The sky is blue. It works! :lol: Single Lambda. atmosphere_single_lambda.jpg Spectral. Same number of samples per pixel. Higher render time but the result is worth it. atmosphere_spectral.jpg Edit. I managed to do a crude derivation of why this works. Basically taking the delta-source ...