Search found 138 matches

by shiqiu1105
Fri Nov 28, 2014 2:03 am
Forum: General Development
Topic: How to sample angular environmental map?
Replies: 3
Views: 3920

Re: How to sample angular environmental map?

MohamedSakr wrote:I think you are looking for this https://github.com/mmp/pbrt-v2/blob/mas ... finite.cpp
I don't think that's what I need. pbrt uses rectangular env map, not the kind in the link I posted.
Thanks for the hint though.
by shiqiu1105
Thu Nov 27, 2014 9:21 pm
Forum: General Development
Topic: How to sample angular environmental map?
Replies: 3
Views: 3920

How to sample angular environmental map?

I found a couple of cool hdr environmental map here: http://www.pauldebevec.com/Probes/

It's all angular map though. Any idea how to sample them with ray tracing? Sample code would be helpful too :)
by shiqiu1105
Tue Nov 25, 2014 12:39 am
Forum: General Development
Topic: Questions about layered bsdfs.
Replies: 2
Views: 3362

Questions about layered bsdfs.

Hey guys, I've been trying to implement a disney styled principle bsdf lately, and I have read http://blog.selfshadow.com/publications/s2014-shading-course/langlands/s2014_pbs_alshaders_notes.pdf and https://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf I got the basic...
by shiqiu1105
Wed Oct 29, 2014 5:17 am
Forum: General Development
Topic: Why does all the major renderer use path tracing?
Replies: 2
Views: 3894

Why does all the major renderer use path tracing?

I am just curious. Why does algorithms based on density estimation like photon mapping weren't as favored by all the major renderers? not to mention metropolis methods. I know the latest renderman has VCM, but still path tracing is most used algorithm, despite it's noise and deffieiency at caustics....
by shiqiu1105
Sat Oct 25, 2014 5:25 pm
Forum: General Development
Topic: How to render soft shadow from directional light
Replies: 4
Views: 4323

Re: How to render soft shadow from directional light

It's pretty easy. Instead of shooting shadow rays in a single direction, you can generate their directions uniformly in a small cone around this direction. Sounds like a good solution! Thanks! Also, an additional question is that, how to render reflected specular high light from delta light sources...
by shiqiu1105
Fri Oct 24, 2014 8:27 pm
Forum: General Development
Topic: How to render soft shadow from directional light
Replies: 4
Views: 4323

How to render soft shadow from directional light

Hi,

My question is really simple.
In ray tracing, sun-like light source is directional, which results in perfectly hard shadows.
In nature, however, shadow of the sun usually is a little fuzzy too.

How to achieve that in ray tracing?

Thanks
by shiqiu1105
Mon Oct 13, 2014 11:46 pm
Forum: General Development
Topic: Smart sampling methods that improves performance.
Replies: 4
Views: 5161

Re: Smart sampling methods that improves performance.

pool2.jpg
Reusing 64 samples. 64spp
pool2.jpg (222.7 KiB) Viewed 5143 times
by shiqiu1105
Mon Oct 13, 2014 11:45 pm
Forum: General Development
Topic: Smart sampling methods that improves performance.
Replies: 4
Views: 5161

Re: Smart sampling methods that improves performance.

Yeah, I also noticed it some time ago when I was exploring their source code. And apparently this trick is still there :) It doesn't reduce the numerical convergence in any way. It only adds correlation between pixels which can potentially be visually disturbing. This reminds me of coherent path tr...
by shiqiu1105
Mon Oct 13, 2014 8:27 pm
Forum: General Development
Topic: Smart sampling methods that improves performance.
Replies: 4
Views: 5161

Smart sampling methods that improves performance.

Hey guys, I have been trying to optimize my own renderer, and I have been comparing my performance against embree 1.1. When we use the same bvh traversal methods, embree is still 30-50% faster than mine implementation. So I was trying to find out why. And I did notice that one thing causing the perf...
by shiqiu1105
Fri Oct 03, 2014 6:13 pm
Forum: General Development
Topic: Questions about metroplis sampling.
Replies: 22
Views: 15439

Re: Questions about metroplis sampling.

Also, about Veach's weighting trick. In the warm up phase, n samples x1...xn are selected with probability p(x), and later we should weight all the contributions by (f(x1)/p(x1) +...+f(xn)/p(xn)) / n right? I don't see people doing this when calculating the final contribution.. Is my understanding s...