Yafray Shadow Flickering

[Samo]

I can't see the video but if you are using a photonmap, that could be the problem
Random nature of photonmap make it different in every time is calculated.
PhotonMap recording is not still implemented in YafRay, but RCRuiz is working on it:
http://www.elysiun.com/forum/viewtopic.php?t=55544

I remember animations by speetiti in the old YafRay site without flickering, I supose they were made without photonmap (I don't know for sure).

[Apollux]

I remember reading somewhere that if you blur a HDRI Light probe and light your scene with it, that helps with the flickering shadows.

[drunksniper]

Note:

I dont use blender nor do I use yafray for regular scene production/rendering.. thus i am only taking my experiences in 3d rendering to give you some insight on what you should be trying to tweak.
------------

First questoion to you is:

What are you rendering? By this i mean.. Radiocity? Global Illumination? Area Shadows? Shadow Maps? Bla bla.

Being that i wont get a quick response, i will give you general answers and experiences similar to this in other high end renderers.

For your information, i work with Mental Ray and Brazil, so i have a general idea of what these little problems are usually the result of.

Flickering shadows.
------------------------
Flickering shadows could be caused by many things. Like i said, it depends what lighting and shading elements you have in the scene. Global Illumination/Photonmapping could be one cause. Usually in the rendering settings there will be adjustments for the number of photons and the number of indirect illumination samples (final gathering/indirect illumination).. Second possible cause could be the lack of sampling in an Area Shadow. Obviously the higher the samples the cleaner more defined the shadow will be, but also the smoother it will be during movement in animation (less flickering because the higher sampling rate is blending it and making less notable during movement).

Another possibility could be bad light interaction with the shader on the plane/ground surface. This usually applies to complex raytraced shaders though, and its very unlikely this is the cause.

i will have to look at yafray and its features/settings to be able to further troubleshoot your problem.

I am downloading it right now and installing blender and i will get back to you with my results when i can.

[CoreyJAvitar]

WoW! THanks a lot for all of your guys's replies!
I am only using the SkyDome method for rendering, thus, there are no photons of any sort, but Apollux's idea might help because I am lighting purely with HDRI, (I don't know what type of shadows YafRay uses, I'm pretty sure that they are all raytraced). Probably what the problem is is that I turned down the shadow quality qute a bit and cranked up some other values 'till I got a blend that rendered fast, and looked good in a still, but that left splotches in the grass and stuff. So maybe it's time for more experimentation. I don't know, maybe I'll try not using HDRI.
drunkSniper: Thanks for the long reply!!
You are really putting forth an effort to aide me! thanks again!

[Gmanx]

I couldn't get your movie to play - plus it crashed firefox. Could you bake some of your lighting solution?

[drunksniper]

WoW! THanks a lot for all of your guys's replies!
I am only using the SkyDome method for rendering, thus, there are no photons of any sort, but Apollux's idea might help because I am lighting purely with HDRI, (I don't know what type of shadows YafRay uses, I'm pretty sure that they are all raytraced). Probably what the problem is is that I turned down the shadow quality qute a bit and cranked up some other values 'till I got a blend that rendered fast, and looked good in a still, but that left splotches in the grass and stuff. So maybe it's time for more experimentation. I don't know, maybe I'll try not using HDRI.
drunkSniper: Thanks for the long reply!!
You are really putting forth an effort to aide me! thanks again!

OK this explains much of the problem. HDRI Is a tricky thing. Its the easiest lighting setup to use, but also be warned its takes longest to render (usually). The problem could now be narrowed down to a few factors:

1. Resolution of your HDRI
2. Sampling of your Ambient Shading and Occlusion from the HDRI Lighitng Information.
--------------
First general Rule of thumb for the poorman who uses HDRI...

DO NOT LIGHT THE WHOLE SCENE WITH HDRI AND EXPECT RENDER TIMES TO BE ReASONABLE ;)
OK.. that out of the way i will carry on.

First of all, you should not rely on the Skydome alone for lights and shadows.
Why?
Because it is meant for ambient light, soft shaodws and color in the scene.

You still need strong light sources and defined shadows because if you use JUST HDRI shaodws.. you WILL get sampling problems because of the ammount of anti-aliasing and sampling that has to be done to properly smooth them. It takes a lot of work to sample a complex distribution of light than to put a light from the direction the "sun" or light source is and control the shadows how you want (.. just use area shadows if you need soft shadows.. or better yet for faster renders... shadow maps)
You cannot brute force lighting... No one does that .. even Pixar/ILM dont do that .. they only brute what they need.. the rest is done the good ol' way.

Basically your problem is coming from the lack of samples in your HDRI Skydome/Skylight Light projection Algorythm.

One quick way to fix this is by blurring the skymap. Another is if course to increase the samples..
i usually use -1,1 Mitchell BUT just see what's available in your renderer for sample adjustments.

I still advise to re-think your lighting strategy and set up concentrated shadow casters (not necessarily lights.. you can have the light OFF but have shadows enabled if your app allows it) Then soften the intensity of the overall Skydome, so that it softens the look of the scene, but not overwelm it with hard shadows that will show artifacts when seen close.. use regular shadows for those..

[Apollux]

you can have the light OFF but have shadows enabled if your app allows it) Then soften the intensity of the overall Skydome, so that it softens the look of the scene, but not overwelm it with hard shadows that will show artifacts when seen close.. use regular shadows for those.. Of course Blender have those light... it is the "shadow only" button on the lighting panel. And for the record, we also have "negative lights" that will substract light from a scene, ala Black Hole.

Other thing you would like to consider is changing from "SkyDome" to "Full GI" so that you have manual control of all the settings.

As far as HDRI render speeds, so far I have been getting fasters renders with HDRI than with manual lights... that if you consider the amount of manual lights that you need to get the same result than with an HDRI.

[drunksniper]

Of course Blender have those light... it is the "shadow only" button on the lighting panel. And for the record, we also have "negative lights" that will substract light from a scene, ala Black Hole.

Other thing you would like to consider is changing from "SkyDome" to "Full GI" so that you have manual control of all the settings.

As far as HDRI render speeds, so far I have been getting fasters renders with HDRI than with manual lights... that if you consider the amount of manual lights that you need to get the same result than with an HDRI.

I never said Use just manual lights, that would defeat the purpose of my last post. I said Use manual lights in conjunction with the skylight to make that flickering less noticable.

[glorund]

Hello,

first sorry for my english. I'm not a pro in Blender nor Yafray, but i have read on the yafray main documentation that Cache utility can produce patterns and flickering on the animation. Cache is useful to interpolate photonmaps values, instead of calculating the light values pixel by pixel. If you are using cache, this is an possible reason.
If not, sorry, but i hope i have help you.
Glaurung

[drunksniper]

Hello,

first sorry for my english. I'm not a pro in Blender nor Yafray, but i have read on the yafray main documentation that Cache utility can produce patterns and flickering on the animation. Cache is useful to interpolate photonmaps values, instead of calculating the light values pixel by pixel. If you are using cache, this is an possible reason.
If not, sorry, but i hope i have help you.
Glaurung

That could very well be one of the reason's. Good Observation

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.