Coloured volumetric shadows with Mental Ray

Category: rendering

Here is a good tutorial on how to set up volumetric lights with Mental Ray:
http://www.jhavna.net/main.php?page=scatter/

It's important to note that the shadow colour is affected by the _transparency_ attribute of the shadowing object's shader, rather than the _colour_ attribute. This has cost me a lot of headaches to figure out.

Compositing layers with motion blurs alpha channels leave black halos.

Category: Rendering

Usually, the halo from motion blur is caused by compositing without pre-multiplied alpha. This means that the RGB value of the transparent pixels are affected by the background colour of that file. Here's a nice workaround in Photoshop, It should be able to be adopt the method to After Effects if linear-dodge is a layer filter option.
link

Aliasing on the edge of foreground objects when using depth of field

Category: Rendering

This is caused by the sudden ending of depth of field's blur post filter in the middle of the object. It's a limitation of the Maya software renderer.There are several workarounds:

• Try to set the focus plane a little before the focus object, and tweak the focus settings.


• Use Mental Ray, which would give you much nicer results.


• Render the scene with dof and the focus object separately, and composite them afterwards.


• Fake dof in post by using a depth map.

Rendering filename bug in 7.0.1?

Category: rendering

It seems that when directly renaming files using the new filenaming syntax in 7.0.1, Maya will automatically append a "_tmp" string to the end of the filename when "%c" is used.

For example, if the filename is "/u/user/renders/file_%c_%4n.%e", then the filename would turn out to be "/u/user/renders/file_camera_0001_tmp.ext". If the camera flag is not used, such as "/u/user/renders/files_%4n.%e", then the file would go under the the folder "$Project_Dir/images/u/user/renders/files_0001.ext". Sucks eh.

The workaround for now is only to correct the "_tmp" by renaming everything using a shell/batch script. ( Or don't use %c at all and have everything saved under $Project_dir/images ).

I don't recall seeing this problem in 7.0. Could this be something that's introduced by the 7.0.1 patch?