AWS Thinkbox Discussion Forums

odd artifacts in render

I’m seeing some very ugly artifacts in a render… There is nothing in the material I am using that would account for these - can someone suggest some revisions to mitigate them? … s.jpg?dl=0
for the image

and … s.c4d?dl=0

for the scene file.

Also, the plane in the scene does not render under K - it renders fine (as expected) using the Standard render. Why wouldn’t this scene element render with K? I need it for the shadows.
Thanks very much.

I am still on vacation with my laptop and don’t have XP or TFD installed on it.
But looking at the Krakatoa dialog, your Density is most probably too high. Try reducing the Final Pass Density Exponent and see if it changes the look. Basically, converting the voxel grid of a TFD to particles will seed particles in the voxels and give them certain per-particle density values. These values will depend on the Spacing of the Krakatoa TFD Source (it was set to 0.5 cm in your scene), and the number of particles per subdivision. As result, if you have very many particles with very high per-particle Density value on each particle, this would result in the TFD voxel grid becoming obvious during rendering. Light will be absorbed very quickly at the very surface of the volume and will create stepping artifacts…

Mesh objects like Plane etc. do not render in Krakatoa. They never have and never will. You are supposed to render them as Mattes (holdout objects) that occlude particles but are otherwise left empty to be filled with a Standard rendering in a compositing application. You need to add a Krakatoa Mesh tag to the object to control its Matte settings. Matte objects can cast shadows. Due to a limitation in the C4D SDK, we could not get particles to cast shadows onto scene geometry in KC4D (it is only supported in the 3ds Max version).
The alternative would be to turn the Plane to millions of particles using for example a PRT Volume or PRT Surface object. These can catch shadows from other particles and Matte objects.

By “reducing” the exponent, I assume you mean to make it a larger (negative) number, so -1 becomes -2 for example (may be a dumb question).
Going to -2 produced a blob on the screen that had no definition whatsoever - much of it was simply washed/burned out. Nothing usable.
So that did not produce any usable result. Maybe when you get back to your office you could try to render. I’ll experiment with some fractional values.
Unfortunate about the plane as the final image i am creating has a lot of volume and when composited against the plane without shadows will look very unnatural indeed. The render/scene is already choking my (high end) workstation and I don’t believe millions more particles would help matters.

Still no luck getting the Mac version to run under the license server. My temp runs out tomorrow so I guess I am out of luck.

I have been poking around the scene file before bed tonight and I have a few quick tips to offer. First off, go into the Render menu and turn off interactive renderer. You have a very tiny interactive region that is constantly trying to render your scene which is slowing things down to a halt on my system. I don’t know if that was intentional or not but it’s probably not a good way to work with this type of scene. Second, I went into the TFD Source object and increased the ‘Voxel Spacing’ to 1.3 and set ‘Voxel Subdivision’ to 1. You can tinker with those settings to get better results. The last thing I did was took all of your scene lights and set them to 50% so it wasn’t so blown out looking.

Here is my quick result:

Another way to go about it is to put your TFD source back to .5 and 0 and then go into the render settings and check ‘Override Density’ and set that to 0.1. Then, set your Exponent (under Lighting and Drawing Pass) to -2. That smooths it out a bit as well…

See here:

If shadows on the plane are a must and you don’t want to do the compositing work then Krakatoa might not be the best for your current project (Sorry Bobo :stuck_out_tongue:) maybe render using TFD directly.

TFD (Set render engine to standard and turned TFD’s render option on):

I hope this post made any sense…It’s pushing 1am and I’m half asleep. :laughing:

Thanks is just great - really very helpful. I wasn;t happy with the look coming from the Standard renderer, which is what led me to Krakaota in the first place, and I really need to study the parameters carefully. But you’ve given me a good jump on that - thanks again very much.

You’re welcome! I am still really learning how to use Krakatoa myself but I am starting to get more familiar with how things work. It’s a little daunting when you first dive into Krakatoa but it gets a bit easier with every render. :slight_smile: Just play around with each setting to see what it does and don’t get discouraged if it takes a while to get the look you are after.

Sorry - I don;t see an “Interactive Rendering” option in the Krakatoa portion of the Render settings or anywhere. Where would that be?

That is a Cinema4D function, not Krakatoa. If you look under the Render menu make sure Interactive Render Region is not turned on. That should speed up your scene navigation.

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