Bizarre Grain in render issues

[cormaction]

Hi Guys,

I'm having a bit of a strange problem here. Basically I'm getting two different looking renders from the same scene. A normal one when I render inside the Softimage application and a grainy one when I use the xsi shell render node.

Here's a very simple example of the issues I'm having:

How it should look (rendered inside the appllication by hitting "render -> current pass"):




And here is how the exact same scene without and changes to settings renders using a bat file on a render node:



Notice the horrible grain in the shadows? I've boosted the levels of both images equally to accentuate the grain. There's nothing fancy apart from area lights here, the material is a deafult scene phong. I thought maybe it would be sampling but why would it render fine inside the application and grainy in the render node? This one has me beat! I figure there must be some kind of disparity between the settings of both but I have no idea what they could be since both the render node and application exist on the same machine. Another strange feature is that the grain remains static, its not like film grain. It's almost as if someone has comped a still frame of grain over the rendered image sequences!

This is badly affecting some jobs we're working on at the minute so any help would be fantastic.

Thanks guys.

[rray]

Which version are you using? I wasn't able to reproduce this on 2011.5. Tried both xsi -render and xsibatch -render, and both raytracing and rasterizer mode (area light with shadows). The two output images had different file sizes, but looked exactly the same, even grain distribution.
Which output file type do you use?

[cormaction]

Hey,
Cheers for trying it out. We're using SI 2011 Service Pack 1 at the moment. We render out to .pic.
Which file format were you using out of interest?

[rray]

I used PIC too so this doesn't seem to be the issue. Tried it on 2011 SP1 too but got no difference either using built-in and batch

[cormaction]

How odd, I did a little bit of experimenting today to see what would happen with different formats and I've been getting the same crappy results with .pic, .tga and 8bit .tiffs. However.....16bit .tiff seem to help remove grain though. I find it very strange though that I would be getting any difference at all rendering inside XSI and in the Batch render. Why would an 8bit pic work fine in the application and not in a batch renderer? Does XSI somehow render the .pics in 16bit inside the application and dither down to 8bit on output?

[xsisupport]

Do you use the same Windows login account when you render from the command line? eg you're not running xsibatch throught a render manager that uses a different user account then the one you use to logon to the machine and render in the UI?

[cormaction]

Cheers for the reply man. No unfortunately, no difference in login accounts. I've done all my tests inside the same account and not through a render manager. Manually making the .bat files.

[cormaction]

Just to clarify, my .bat file would read something like:

xsi -r -scene \\UNC Path to the directory\Scene_Name.scn -pass PassName -startframe 1 -endframe 1 -skip on -continue

[xsisupport]

For testing purposes, could you upload the test scene, or a script that recreates the scene?
Or I could send you a dropbox link.

I'll try the scene here.


PS - While that command line will still work, the syntax is now xsibatch -render
The -r -scene flags are deprecated, but are mapped todo the same thing as -render.

[cormaction]

Hey. Yeah, I've done a new scene, really really basic, just a single spot light and a sphere. I'll host it on my site for the moment:

http://www.rightpsyche.com/Files/GRAIN_TEST.scn

(this scene is a less extreme case as then grain is deep in the shadows...but the bad effects of this are effecting scenes with a lot more light in them than this)

So, to test this scene, render out one image from within XSI and another from a batch render.

Bring both files into photoshop and layer them on top of one another and add a levels adjustment layer on top of them both. Boost the levels till you esentially get a black and white image and you should notice that the line of the spheres shadow in the batch file image is grainy and pixellated whereas the one from inside the application is normal.

Hope this makes sense/ works!

Cheers again, much appreciated.

[cormaction]

By the way, I tried the .bat with the new syntax and got an error reading:

' FATAL : No scene filename given to render or export

I assume I've ballsed up the syntax so here's what my .bat reads:

xsibatch -render -scene \\UNC Path to the directory\Scene_Name.scn -pass PassName -startframe 1 -endframe 1 -skip on -continue

Just thought I'd mention that in case it had any relevance.

[xsisupport]

I tried and I don't see any difference.
imf_diff says the two images are the same (I don't have Photoshop).

Do you get this same problem on other render nodes?
If not, try renaming your User folder and running runonce.bat, just to try with a known good factory-default setup.

I might run Process Monitor when you render with xsibatch, to verify that the right xsibatch is running and its loading all its DLLs from the right place (eg make sure xsibatch is not running with the wrong environment and loading DLLs from the wrong folder).


The syntax is:
xsibatch -render "\\server\project\scenes\test.scn" -pass thisPass -frames 1-3

[cormaction]

Hey

Yeah, this problem occurs on all the render nodes too. If you load your two rendered images in Imf_Diff and boost the gamma to something really high like 4.0 and hit play there is no difference at all?

I downloaded process manager (haven't used it before so I'm not entirely sure what I'm doing in it) but when I ran the bat file I did find something strange, XSI 7.5 seemed to run briefly, I've attached an image of the bit where 7.5 pops up, you can see above it, it's loading 2011 SP1 though:



How would I find out which environment it is loading though?

Cheers and thanks again.

[xsisupport]

You want to make sure that it is the xsibatch from the Softimage 2011 SP1 folder that starts the job, and that it loads 2011 SP1 dlls.

Here's a quick video (no audio):
http://www.screencast.com/t/wwEELHCiJX


imf_diff said the files were identical, so I didn't load the result

[cormaction]

Really appreciate you going to all the effort man, thanks a mill. Yeah, XSI seems to be loading all the correct DLLs and the setenv.bat is from 2011 too so it seems to be loading the correct environment.

With some experimentation with the gamma we've been able to get something working.
Basically the way we were working (and I believe it's the correct way) is that in our Display -> Color Management settings our gamma was set to 2.2 and we would check on the "Apply Gamma Correction" on the pass when rendering and this yields the bad result from the batch renderer (but fine from the application) I've been talking about...

However, if we mess about with the process and set our gamma to 1.0 in the Color Management settings and add a photographic exporure mia shader to the camera and set that at 2.2 the grain problem disappears in the batch render. Do you think the gamma when it's set to 1.0 is being interpreted differently in the batch renderer somehow (I know this makes little sense)?

The mystery continues it would seem.