Twilight Render User Forum

Hi Gang,

I have done several animations with no problem, but this latest simple flyby animation seems to be producing a number of black square artifacts. Wondering if anyone has any ideas on how to fix this?

Here is an example: http://www.yjprod.com/image/dt/DT.htm

Simple animation, default settings, rendered as JPG and BMP - same results.

Regards,


-S

I've never seen that one before. (the black square issue)
Can you give us some details about the scene, lighting, materials, render settings?

Hi Fletch,

Thanks for the quick reply. Here is the file: http://www.yjprod.com/image/dt/LOGO3D.skp

No special lighting (just a spherical sky)

If you need the sky jpg (a.k.a. it's not coming with the file) it can be found here: http://www.yjprod.com/image/dt/13749351 ... a525_o.jpg

The surface is entirely NK Metals/Chrome-Perfect Reflection.

Regards,


-S

Purchasing Twilight will remove limitations and allow you to export via .xml.
Removing Twilight watermarks from images is against the ULA.

Were you using a special-made render setting?
The file does not show one loaded.

Try this -
instead of the N-K metals (They are best for rendering in Easy09 and 10, although they usually work well with Easy1-7, Easy08 doesn't like them for some reason.)
Use Template>Metal>Silver
Change Shininess number from Default 200 to be 100000 (5 zeros)
Change color of gray metal to be This should look very similar to the chrome and render just as quickly (hopefully without artifacts).

Using the settings above, It's rendering one frame per second artifact free on Low+ setting on the machine I'm using.

*edit* it rendered 336 flawless frames (making the video at 24fps) in 13 minutes. Rendering speed of animation averaged around 27 frames per minute.

Hi Fletch. No special made render setting. Just selected "Low".

Trying the following:

Prelim: Fewer artifacts and smaller, but still there.
Low: Artifacts
Low+: Same as Low
Medium: Same as Low
Removed all objects and just did the background with "Low": Artifacts still present.
Removing background image, putting objects back in, and putting in "Physical Sky": Artifacts still present.
Removed all materials not used: Artifacts still present.
Tried Exterior Daytime (didn't allow it to finish cuz taking too long): No artifacts.
Tried Interior Progressive (didn't allow it to finish cuz taking too long): No artifacts.
Tried Clay Light Pass: No artifacts
Photon Map (Low): Artifacts present
Path Tracing: No Artifacts.

-S

Like Fletch said, I've never seen that happen.

How many threads are you using, and how many CPU cores do you have?

EDIT: I can reproduce the problem if I choose more threads than I have cores. To get the magnitude of glitches that can be seen in your animation, I had to go up to 16 threads, and I only have 2 cores. Try reducing the number of threads. Worst case, set it to 1 thread and I bet it will make the glitches go away completely.

Hi Chris,

The only I found in Twilight is to "Use Maximum Suggested Threads" on the Advanced tab in rendering. It is checked.

The machine is an i7/920 - not overclocked but liquid cooled. nVidia Quadro 600 video card.

I will try forcing a lower number of threads per your edit and let you know...

EDIT: Ok dig this - one thread had no artifacts. 4 threads had the artifacts again. 2 threads had very small and very infrequent artifacts (single pixel). Even more interesting - with 1 thread the renders ran at about 3 times faster....? My CPU has 32 threads and 4 cores so whassup with that?
-S

That is odd indeed.

I'm pretty much certain that the artifacts are caused by multi-threading and the more threads, the bigger the problem (when there is a problem). However, the problem is virtually unheard of until now so it probably has something to do with your scene. As to what that is... <shrug>

Obviously setting your threads to 1 isn't something you are going to need (or want) to do under most circumstances but when those black boxes show up, it's worth a shot.

interesting. (maybe that's not the right word)
my test was rendered with corei7920 oc'd to 3.6Ghz
There are cases where multithreading slows down a render, this is known. In the case of smaller sized renderings because of some bottlenecks in the way multithreading works.
http://www.kerkythea.net/phpBB2/viewtop ... 3699#63699

So, it appears that the render is getting done TOO quickly, and it's not able to "pull itself all together" before the file is saved and is moving on to the next task. (for lack of a good technical explanation)

I had a similar problem a while ago but I was too much in a hurry with the video below and could not ask for help instead I just edited the frames where it was present except maybe 2 or 3.


The squares only appear in the top left corner but watch carefully as there are now only very few. Sorry for not reporting it back then but I really had no time and later I forgot about the whole thing.

I have a dual core machine and of course, I was rendering it with both cores. It is not a "real" clay render (i.e. not clay render settings) but some general colour used on the model (except for the windows).