strange artifacts in rendering

radiance-general
1

Hi everyone,

I am getting strange artifacts in my renderings, and am wondering which
parameters to tweak in order to get rid of them. The artifacts look like a
white, or sometimes half-black and half-white, patch at random locations.
See below for examples:

http://minjung.ca/tmp/artifacts1.png
http://minjung.ca/tmp/artifacts2.png

I've tried (1) setting ad = 4096, as = 1024, and (2) setting aa = 0, ar =
0, but neither of these two settings fixed the problem. Do you have any
idea what might be happening? Here are some possibly relevant factors:

- The object is completely Lambertian.
- The only light source in the scene is a glow source that is positioned
behind the camera, and covers as much of the sky as possible.
- I don't think I've ever encountered such artifacts with untextured
stimuli. I could be wrong, though.

Thanks in advance!

MJ

2

Hi MJ,

Can you send me your model & rendering parameters off-list. I won't know what's going on until I play with it.

Thanks,
-Greg

···

From: Minjung Kim <mkim85@gmail.com>
Subject: [Radiance-general] strange artifacts in rendering
Date: August 17, 2015 5:30:37 PM EDT

Hi everyone,

I am getting strange artifacts in my renderings, and am wondering which parameters to tweak in order to get rid of them. The artifacts look like a white, or sometimes half-black and half-white, patch at random locations. See below for examples:

http://minjung.ca/tmp/artifacts1.png
http://minjung.ca/tmp/artifacts2.png

I've tried (1) setting ad = 4096, as = 1024, and (2) setting aa = 0, ar = 0, but neither of these two settings fixed the problem. Do you have any idea what might be happening? Here are some possibly relevant factors:

- The object is completely Lambertian.
- The only light source in the scene is a glow source that is positioned behind the camera, and covers as much of the sky as possible.
- I don't think I've ever encountered such artifacts with untextured stimuli. I could be wrong, though.

Thanks in advance!

MJ

3

Just forwarding this to the mailing list in case as an additional warning against installing Mac OS X Yosemite (10.10.x). As if the multi-processing bug were not enough, there seem to be other problems with instances and/or textures (not sure) on that platform.

I may try investigating this on the weekend, but I don't hold out much hope for a resolution.

-Greg

···

Begin forwarded message:

From: Minjung Kim <mkim85@gmail.com>
Subject: Re: [Radiance-general] strange artifacts in rendering
Date: August 19, 2015 4:58:24 PM PDT
To: "Gregory J. Ward" <gregoryjward@gmail.com>

Hi Greg,

I think the problem might indeed be with OS 10.10. None of the 20 scenes that I rendered on OS 10.9 had any issues, whereas more than half of the 20 on OS 10.10 did. Please see attached files for examples.

Thanks for your help!

MJ

On Wed, Aug 19, 2015 at 4:33 PM, Minjung Kim <mkim85@gmail.com> wrote:
I'm going to render a bunch of other blobby objects on 10.9, and see if I get the problem here. I'll let you know what I find out.

Thanks!

MJ

On Wed, Aug 19, 2015 at 4:30 PM, Gregory J. Ward <gregoryjward@gmail.com> wrote:
Thanks, Minjung.

I guess we can add this to the list of bugs under Mac OS X 10.10, which to me has been a disastrous release. I seriously doubt I will be able to fix problems on this platform, but I'll give it a try when I have some time.

Cheers,
-Greg

From: Minjung Kim <mkim85@gmail.com>
Subject: Re: [Radiance-general] strange artifacts in rendering
Date: August 19, 2015 4:16:50 PM EDT

Hi Greg,

Thanks for your help! I am still unable to get the artifacts to come back -- but only on my current machine (late-2013 iMac, 21.5 in., OS X 10.9). If I run the same code on a different machine (late-2013 iMac, 21.5 in., OS X 10.10), I reliably get the artifact. Isn't that strange?

Attached are the files that I used. To run, please use the following commands:

oconv square.rad > square.oct
oconv scene.rad > scene.oct
rpict -x 1024 -y 1024 -vh 12.018 -vv 12.018 -vp 0 -0.57 0 -vd 0 1 0 -vu 0 0 1 -av 0 0 0 -vtv -ab 1 scene.oct > scene.pic
pfilt -1 -x 512 -y 512 -e 1 -r 0.6 scene.pic > scene.hdr

In scene.rad, the square is incorporated as an instance. I know that I don't really need to instance the square since I only have one, but the scene with the artifacts was using instances, so I thought it would be better to send you the code as is.

If anything is unclear, please let me know. Thanks again!

Regards,

MJ

On Tue, Aug 18, 2015 at 7:00 PM, Minjung Kim <mkim85@gmail.com> wrote:
Hi Greg,

Thanks! I'm putting together the files, but I'm unable to replicate the problem using my latest code, though I don't think I've changed anything substantial. I'll get back to you once I can reliably replicate the artifacts.

MJ

On Mon, Aug 17, 2015 at 9:04 PM, Greg Ward <gregoryjward@gmail.com> wrote:
Hi MJ,

Can you send me your model & rendering parameters off-list. I won't know what's going on until I play with it.

Thanks,
-Greg

From: Minjung Kim <mkim85@gmail.com>
Subject: [Radiance-general] strange artifacts in rendering
Date: August 17, 2015 5:30:37 PM EDT

Hi everyone,

I am getting strange artifacts in my renderings, and am wondering which parameters to tweak in order to get rid of them. The artifacts look like a white, or sometimes half-black and half-white, patch at random locations. See below for examples:

http://minjung.ca/tmp/artifacts1.png
http://minjung.ca/tmp/artifacts2.png

I've tried (1) setting ad = 4096, as = 1024, and (2) setting aa = 0, ar = 0, but neither of these two settings fixed the problem. Do you have any idea what might be happening? Here are some possibly relevant factors:

- The object is completely Lambertian.
- The only light source in the scene is a glow source that is positioned behind the camera, and covers as much of the sky as possible.
- I don't think I've ever encountered such artifacts with untextured stimuli. I could be wrong, though.

Thanks in advance!

MJ