ShadowPass is a Material
based on the standard Matte/Shadow, but designed to be used solely
for shadow catching.
The problem with the Matte/Shadow material is
that it does not support coloured lights - internally it calculates
colour data for the shadow component, but then uses just the luminance
of the colour shadow data to dump into the alpha channel.
This material plugin outputs colour shadow data
in the RGB, so where Matte/Shadow does this:
in the same scene ShadowPass produces this:
The alpha of the ShadowPass result is not used
for compositing so ShadowPass outputs solid alpha (makes it easier
to see what was actually rendered).
The only addition over the matte/shadow material
is a 2-sided option - and is in fact the only UI control, a single
checkbox to enable/disable 2 sided rendering.
This material IS
Mental Ray compatible - there is an accompanying Mental Ray shader.
TIP: while this
material is Vray compatible, you can get the same effect with the
Vray Material Wrapper - just set the colour of its shadows to white
(rather than the default black) and you will get a similar result
to the ShadowPass material in the RGB (but with GI etc. in there
Best used rendered to a float format, and composited
in a float-capable compositing app. Half-Float OpenEXR is a good
choice. To composite with this (assuming in a 3rd party compositing
app such as Fusion, Combustion) you simply invert it, and then multiply
the RGB over your plate (don't affect alpha). Here is a brief breakdown:
First image is a single frame render of the
holed box with shadows from the scanline renderer:
Then the passes broken out and comp'ed:
and from there you can adjust your shadows etc.:
(note the blocky shadowing appearing on the front side of the box
in its shadow pass is actually correct and doesn't cause an artifact
in the final comp of these elements)
You can download a max8 scene setup rendering
the above images with RPM here
(object property capture used to swap materials and visible to camera
ShadowPass is freeware
Use it however you like, but the usual not responsible
for any damage caused applies.
ShadowPass for 3dsmax7 and 3dsmax8 (not R6 for the
installer, for the R6 plugin download this
and put in your plugins path)
Run the ShadowPass installer, which puts
it into your plugins directory (and the mental ray stuff into the
MR auto load directories) and then restart 3dsmax.
It is a Material so appears in the Material Editor.
Contact email@example.com with any bug info.
Scene files demonstrating problems are much easier to troublshoot.
Credits: ShadowPass was
written by Grant Adam, code based on the Matte/Shadow material in
the SDK. Big thanks to Master Zap for his help with MR shaders.