YafaRay tests

[enricocerica]

@Lynx: I used a texture with alpha channel, it works fine with direct lighting and pathtracing but not with photon mapping, I get a black surface instead of the texture with transparence. I tried all the combinations, it seems to be a bug. Any idea how to fix that ? Thanks

[Samo]

I would like to test the new yaf(a)ray on some architectural scene. I Would like most to test the photon based rendering, but I see that the tutorial page, miss that part.

Can please someone help me indicating some tutorial, or base setting to start some testing?

Yaf(a)ray settings on photons are more or less the same than yafray 0.0.9 ones:

Depth: Number of bounces for photons, the more the better. Since there is not an independent setting for caustic photons, I suppose that this setting is used for both.

Photons: Number of photons to shoot.

Diffuse (?) Radius: The same as the 'Radius' parameter in yafray 0.0.9.

Search: number of photons to mix, like yafray 'Mixcount'.

There is not irradiance cache implemented yet. To achieve the same results than using path tracing, you should use 'final gathering', a good amount of final gathering samples (16 for instance) and quite high antialiasing settings (5x5). I've comproved that 'gauss' filter reduces noise a bit as well, compared with the other filters.

[draw]

I've done a little test

1) photonmapping


2) pathtracing



same rendertime, but too noise in this

[quibodi]

@Draw: ...And Pathtracing dosn't like sofas.
I noticed too that Pathtracing is much slower than photon mapping.
If you try with 128 or more samples, you will get less noise, but the rendertime will increase a lot. The Lighting seemes to be a little more physical correct with Pathtracing.

[Samo]

< Left, path tracing with 64 samples, 3x4 Box AA
> Right, Photons + Final Gathering, 16 FG samples, 5x6 Gauss AA
Notice render times.



You can download the scene here. SET 1 is pathtracing, SET 2 is photons + FG:

http://www.zshare.net/download/207471670646c6/

[mana]

uhm where can i read about the difference between pathtracing and photons as a rendering technic? Well what i mean is a summary and advice on what do use when eh? .. given i get to use yafaray on my ubuntu

[Samo]

uhm where can i read about the difference between pathtracing and photons as a rendering technic? Well what i mean is a summary and advice on what do use when eh? .. given i get to use yafaray on my ubuntu

Use google. There are literally hundreds of docs talking about path tracing, photon mapping and other ray tracing techs. In the yafray wiki there is also some tutorials.

Path tracing is a lighting calculation in which rays are shoot from the camera. These rays bounce using stochastic algoritms untill some of them find a light source. Then the light contribution along the path is calculated, taking into account surfaces properties.

Photon mapping is a lighting calculation in which rays are shot from light sources, and bounce around to make a photon map. It does not matter whether they reach the camera or not. The photon map can be used later by a path tracing pass, but this time the path tracing pass will perform a single bounce, just to 'see' the photon map. It can be used also by a final gathering pass.

[mana]

thanks. Your resumé made it clear to me.

[quibodi]

@Samo: Thanks for the testfile. With this scene your settings work pretty good. But I tested them with another scene with less direct light and there pathtracing did not work very well with this settings, as you can see in the pics. I tested a lot, but only increasing the path samples to something around 200 brought better results. And than the Rendertime was 15 times higher than with photon mapping. Do you have any idea to reduce it without loosing quality?


b.t.w: studying your settings i finally found out, what is the meaning of AA-Samples, AA-Passes and AA-inc.samples.
3 Passes, 4 Samples, 2 inc.samples means: 1 Pass with 4 Samples and 2 additional Passes with 2 Samples. Surely you knew this, but i was irritated by your "3x4 box AA"

[Samo]

@Samo: Thanks for the testfile. With this scene your settings work pretty good. But I tested them with another scene with less direct light and there pathtracing did not work very well with this settings, as you can see in the pics. I tested a lot, but only increasing the path samples to something around 200 brought better results. And than the Rendertime was 15 times higher than with photon mapping. Do you have any idea to reduce it without loosing quality?

I'm guessing here, but I think that the result you've got using path tracing is pretty normal.

First of all, let me clarify that when you use Full GI in YafRay 009, you are using in fact path tracing. YafRay 009 should deliver similar result using those samples if Irradiance cache is deactivated. Take into account that YafRay 009 Full GI - Best Quality is equal to 2048 samples.

We won't get faster results with yaf(a)ray path tracing untill irrandiance cache is back, although Yaf(a)ray pathtracing should be more efficient since it uses importance sampling AFAIK, but I suppose it can not avoid the classic problem that every path tracing implementation has got, the 'visibility problem', which is explained by Jandro here:

http://wiki.yafray.org/bin/view.pl/User ... ayLighting

Path tracing is not that optimal when light sources are relatively difficult to reach from the camera point of view, since rays use montecarlo stochastic algorithms for bouncing. In my scene there are five relatively big and accesible light sources, so I can achieve a good result with a relatively low number of samples.

[Lynx]

@Lynx: I used a texture with alpha channel, it works fine with direct lighting and pathtracing but not with photon mapping, I get a black surface instead of the texture with transparence. I tried all the combinations, it seems to be a bug. Any idea how to fix that ? Thanks

Not really a bug, photon mapping is just not really finished yet, it can't gather caustics yet, i'm probably spending too much time investigating new GI algorithms...

We won't get faster results with yaf(a)ray path tracing untill irrandiance cache is back, although Yaf(a)ray pathtracing should be more efficient since it uses importance sampling AFAIK, but I suppose it can not avoid the classic problem that every path tracing implementation has got, the 'visibility problem', which is explained by Jandro here:

Basically, there is indeed no magic that does much faster path tracing then before, however the old code could only simulate diffuse and specular reflections, and light sources were not handled very efficiently because of the fact that the path tracing was implemented as a light source itself too.
Also a lot of other details help here and there, like light sources/materials were made to allow multiple importance sampling, the QMC sampling was reworked, scene has global kd-tree etc...
But with the new capabilities also came new sources for noise, like glossy reflections, and irradiance cache is not well suited for glossy reflections either. Only bidirectional methods can remedy this, but they're a magnitude more tricky...

[save]

Hi all,
Thank to Samo, I've made a lot of testes. I've played with all parameters, and read all documentation.
Anyway, I think that in my settings something is wrong.
This because, I have a scene, with only 3 meshes (cubes), 1 light (sun) and no materials. And the time of the rendering seems too high for that scene.

Here are some test, with times and all settings.







http://www.esnips.com/web/Yafray-Test/yaf-a-ray-05.jpg

http://www.esnips.com/web/Yafray-Test/yaf-a-ray-09.jpg

http://www.esnips.com/web/Yafray-Test/yaf-a-ray-12.jpg

And this is the file I used.

http://www.esnips.com/web/Yafray-Test/TEST-yaf(a)ray.blend

Could please someone verify what could be the better parameters, with that type of scene?
The complete scene has many other meshes, it is the interior of a commercial center, with opened ceiling. So I suppose that with the complete scene the render time could becme too long.

Thakyou very much .
Save

[enricocerica]

@Lynx: I used a texture with alpha channel, it works fine with direct lighting and pathtracing but not with photon mapping, I get a black surface instead of the texture with transparence. I tried all the combinations, it seems to be a bug. Any idea how to fix that ? Thanks

Not really a bug, photon mapping is just not really finished yet, it can't gather caustics yet, i'm probably spending too much time investigating new GI algorithms...

Ok, thanks for the feedback Lynx, can't wait to get a new version with photon mapping finished. Can we expect a new version soon ? Hey, up to you

[quibodi]

@Save: Are you joking? Under 3 minutes ist definetly lo long time with this resolution, even if it is a simple scene! IMHO your settings seem to be OK for a quick testrender.

[save]

@Save: Are you joking? Under 3 minutes ist definetly lo long time with this resolution, even if it is a simple scene! IMHO your settings seem to be OK for a quick testrender.

Really?? Excuse if this seem a strange request.. I was expecting very lower times.. may be its passed too long time from my last rendering with yafray

What about the quality
What is to be improved?
thanks
save