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Antialiasing issue
show user profile  mike_renouf
I THINK, after extensive reading and fiddling with computer settings, that I've got my system set up to work in a linear colourspace. I'm using mentalRay and I've got some really nice renders to come out of the system recently.

Today I found this page:

which suggests that in order to preserve the linear way of working, you can set the burn, midtones and shadows on mentalray's photographic exposure control to certain levels.

I did so and I was really pleased with the results - interior renders came out with great colour and the light areas were nicely over exposed as you'd expect from a photo.

However, I got this dodgy antialiasing problem where there is high contrast. Any ideas what I'm doing wrong? Perhaps I've just misinterpretted the settings..?


read 688 times
9/20/2011 8:46:03 PM (last edit: 9/20/2011 8:46:03 PM)
show user profile  mike_renouf

read 646 times
9/22/2011 9:13:42 AM (last edit: 9/22/2011 9:14:45 AM)
show user profile  Nanne
Your using a 32bit float Frame Buffer which mean no colour values are clamped so the AA-filter can't smooth it out. Try switching to the 16bit integer Frame Buffer. And you can try adding the Glow Camera Shader to bloom out the bright areas.

You seam to have some banding issues on the right chair. Or it might be the lighting that isn't smoothed out properly.

Kristoffer Helander
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read 638 times
9/22/2011 10:06:58 AM (last edit: 9/22/2011 10:06:58 AM)
show user profile  mike_renouf
Thanks Nanne! That's solved it.

You're right about the chair too - it was a cheap final-gather solution in that render, so the chair does have some splotches on it. I'll re-render with the new settings and post when I get a chance.

I just had a play about with another scene rendered using the 16bit frame buffer though and I'm really pleased with the improvement.


read 614 times
9/22/2011 2:34:26 PM (last edit: 9/22/2011 2:34:26 PM)
show user profile  Nanne
Glad I could help :) Please post a rendering with the 16-bit Frame Buffer, I would like to see the difference.

Kristoffer Helander
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read 610 times
9/22/2011 3:54:35 PM (last edit: 9/22/2011 3:54:35 PM)
show user profile  mike_renouf

Here's a re-rendered version with slightly improved material reflections and final gather solution. It's done with the 16bit frame buffer and I think its a bit less jaggy - still not quite as I'd have hoped, but as you say, with a glare pass and some post it'll do nicely.

Here's another view of the same scene. It's a re-render of a scene I made ages ago, but I tinker with it and update it as I learn more:

read 589 times
9/22/2011 11:24:29 PM (last edit: 9/22/2011 11:24:29 PM)
show user profile  Nanne
Strange black border you get, I' not sure what's up with that actually...

Could you post your scene, so I can download it and do some test rendering myself, see if I can figure it out?

Kristoffer Helander
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read 581 times
9/22/2011 11:38:50 PM (last edit: 9/22/2011 11:38:50 PM)
show user profile  BishBashRoss
Looks like some sort of Sharpening AA filter.

read 578 times
9/22/2011 11:43:42 PM (last edit: 9/22/2011 11:43:42 PM)
show user profile  Nanne
That's funny, now I'm getting this very same problem in a scene that I have rendered many times before without any problem... hmm...

Kristoffer Helander
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read 570 times
9/23/2011 12:27:39 AM (last edit: 9/23/2011 12:27:39 AM)
show user profile  mike_renouf
Cheers again Nanne - I'll try to upload something over the weekend, but I can't do it at today as I'm at work.

The scene was rendered with my usual settings.

Samples per pixel:

Filter: Mitchell
Width: 4
Height: 4

Spatial Contrast 0.051 for all settings

Lock samples off
Jitter on

Frame buffer - I used the 16bit Integer version as you suggested.

Scanline is enabled
Shadows and displacement mode is set to Simple

No camera effects are enabled.

Hope this helps?

Best regards,

read 552 times
9/23/2011 9:20:18 AM (last edit: 9/23/2011 9:20:18 AM)
show user profile  BishBashRoss
get rid of the Mitchell whatever it is filter and replace with something with no sharpening. Try area.

read 549 times
9/23/2011 9:30:51 AM (last edit: 9/23/2011 9:30:51 AM)
show user profile  mike_renouf

Thanks Ross - you've sussed it. I don't have "Area" as an option (that might be cos I'm on max 2009, but I switched to Triangle and that looked much nicer without the hard blackened edges. I'll need to tweak the height and width, but that's a job for later on.

read 547 times
9/23/2011 9:46:45 AM (last edit: 9/23/2011 9:46:45 AM)
show user profile  BishBashRoss
No probs!

read 541 times
9/23/2011 10:01:09 AM (last edit: 9/23/2011 10:01:09 AM)
show user profile  mrgrotey
Just so you know, area is a scanline filter not mental ray. That's why you didnt have the option.

read 534 times
9/23/2011 10:33:04 AM (last edit: 9/23/2011 10:33:36 AM)
show user profile  BishBashRoss
Aye, sorry. Don't use MR too much these days so it was a bit of a guess.

read 523 times
9/23/2011 11:27:06 AM (last edit: 9/23/2011 11:27:06 AM)
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