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adrian haynes
11-23-2005, 09:28 PM
i've been getting a weird flicker with hdri lighting in mental ray. It started when I switched from 6.5 to 7. I'm doing exactly what I did in 6.5 to render, but i get this error. I'm including a gif of a few frames, its easiest to notice if you look at the half sphere element at the top of the robot.


I'd appreciate any help, as I am somewhat new to mental ray, and hdri.

http://i15.photobucket.com/albums/a379/adrianhaynes/Comp1.gif

adrian

revilo3D
11-24-2005, 06:30 AM
are you using indirect lighting with your HDRi or is your HDR emitting light?

adrian haynes
11-26-2005, 05:08 PM
i have my hdri emitting light, no other lights in the scene

eddgarpv
11-26-2005, 06:10 PM
I've had the same issues with diffuse passes using IBL nodes emitting light and the solution in my case was to use higher values in Quality U and V.

adrian haynes
11-26-2005, 06:19 PM
i tried boosting up the quality u v to 1024 already, and I still get the error.
i'll try turning it up even higher and rendering again to make sure.

adrian haynes
11-26-2005, 06:41 PM
boosted it to 2048 and still no luck

revilo3D
11-26-2005, 09:13 PM
i personally perfer to completely scrap IBL light emission .. it is far to intensive. U and V is baasilly diviiding up the HDR into lights into that value i believe.. eg.. sampling 1024 in u and v is like having 1048576 lights in your scene , which is totally overkill and gives you the horrible render times you must be having.

The best option is to sample the HDR and create a light source of your own from the HDR. Similar to that lie a dome light rig. The results work great and is much faster. Look into IBL tools to do this... this will give you the option to create a light rig that matches your HDR, either via a traditional dome lighting rig or a new mental ray light.. that works in a similar fashion.

I think it should solve any flicker problems you may be having too :)

adrian haynes
11-27-2005, 12:08 AM
i personally perfer to completely scrap IBL light emission .. it is far to intensive. U and V is baasilly diviiding up the HDR into lights into that value i believe.. eg.. sampling 1024 in u and v is like having 1048576 lights in your scene , which is totally overkill and gives you the horrible render times you must be having.

The best option is to sample the HDR and create a light source of your own from the HDR. Similar to that lie a dome light rig. The results work great and is much faster. Look into IBL tools to do this... this will give you the option to create a light rig that matches your HDR, either via a traditional dome lighting rig or a new mental ray light.. that works in a similar fashion.

I think it should solve any flicker problems you may be having too :)


That sounds like a good idea. Although the render times aren't bad at all with a scene as simple as this. I believe I get a one to one and a half minute render for a 720 480 image. this will help me on bigger scenes. Do you know where's a good place to get info on IBL tools or any suggestions on a starting place?

thanks again,

revilo3D
11-27-2005, 04:40 PM
the place to start is here...

http://www.thereisnoluck.com/plugins_iblTools.php

I find the documentation a little bit thin based on that they are very technical and a tricky to work out what does what for the not so technically minded... But its managble to work out and get a grasp off...and its definately a good solution - for any scene.

adrian haynes
11-29-2005, 02:59 PM
thanks for the link, i played around with my scene a bit, and I found out the probem wasn't with HDRI, but with FG. I found a tutorial on fg flicker on the alias web site, which didn't help since the scripting didn't work for 7 (must not have been updated).

this is apparently the fix
"By using the “Final Gather View” dynamic attribute, it is possible to sample Final Gather scene irradiance using image space or raster space. Typically, this will give much finer resolve than with the world space approach above. Using the Final Gather View attribute in effect tells mental ray for Maya to calculate Final Gather sample point irradiance, search pattern size, using raster space pixel radius dimensions, rather than world space centimeters.
The Final Gather View attribute is available with mental ray for Maya v6.0 on a shape node basis or dynamically (to be used for the entire scene) via a user created attribute that can be enabled on the miDefaultOptions node.
Open the movie file flicker_Resolved.mov to view a rendered sequence that makes use of the Final Gather View flag functionality."


this is the mel commands that aren't working

select miDefaultOptions; (works)
addAttr -ln finalGatherView -at bool miDefaultOptions; (gets tripped up on this line)
setAttr miDefaultOptions.finalGatherView 1;

any insight on where to go to get this?

I'm getting this issue on scenes using FG without HDRI also, and don't have time to mess with IBL tools since stuff is due in a few weeks for the end of the semester (and teachers are completely clueless about mental ray at my school)

thanks

frogspasm
11-29-2005, 06:11 PM
Run this command:

select miDefaultOptions;

Then go to the channel box, right click on one of the attributes and select Channel Control.
Under the keyable tab there will be 3 windows. Scroll down the "non-keyable hidden" window until you see finalGatherView. Click on one of the buttons at the bottom to move it to the keyable side. Now you should be able to see it in the channel box for miDefaultOptions.


setAttr miDefaultOptions.finalGatherView 1;
This command really is the only one you need to worry about. It turns on the attribute.
The other stuff just lets you view it and turn it on or off in the interface.

~Mike D.

frogspasm
11-29-2005, 06:44 PM
Actually, I'm not sure this function is working (at least in 6.5, might be fixed in 7)
According to this thread:

http://forums.cgsociety.org/showthread.php?t=228939

~Mike D.
Trying to fix my flicker problems too.

revilo3D
11-30-2005, 05:21 AM
are you using indirect lighting with your HDRi or is your HDR emitting light?

why do you think i asked this question! Indirect lighting is things like FG and GI... something that is actually prone to flicker. Not HDRI.. I was wondering this from the start.

You have a few solutions... i found the basic start workflow is to set min max radius to an appropriate value and start increaing rays till flicker is acceptable.

the second is to go around you scene with you camera and "collect" fg points(if applicatable to your animation). You can then "FreeZE" the fg map.

Another is the bake the lighting infomation down to the texture.

personally i would consider using IBLtools or (new tool eying up) - Realfake HDRI, and an occulsion pass :)

PS.. emiiting HDRI light AND FG i think again is overkill and reduduant... by nature FG is collects radiance infomation from its surrounding world.. like a HDRi image.. but your HDRi is illuminating the scene anyway already. Maybe it does look better i dunno... but think it really may not be neccerary.

adrian haynes
11-30-2005, 06:42 AM
thanks for the reply. This method didn't get any mel error, but after applying the setting, my model actually had more flicker than before. Tomorrow i'll check back with the original tutorial to see if other settings need be tweeked.

adrian haynes
12-02-2005, 08:45 PM
alright, althought I greatly reduced the flicker, I haven't had luck in getting rid of it all together,

so...

I'm trying the IBL tools solution now, and have run into a problem. I converted my hdri image to a floating tif, and ran the light map generation program as instructed and got the error of "Cannot determin filename parts, exiting"

any help further help would be appreciated

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