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[Vray] - Shadow isolation - MatteShadow vs Alpha Manipulation
show user profile  9krausec
Morning guys,

I'm trying to figure out the best way to isolate my shadows using Vray. So far I've been attempting two possible ways to do this-

1) Alpha manipulation using a matte object (Vray material wrapper) and having it affect the alpha pass.

2) MatteShadow render element

I'd very much like to use the MatteShadow pass to isolate my shadows as I use the Alpha for object isolation/masking in post. The shadows being included in the alpha are something I'd like to avoid if all possible.

Although both methods work, the Alpha manipulation works far better as far as shadow quality (see below)-

Alpha Manipulation-
 photo alpha_zpsmdrxtgbz.jpg

MatteShadow Pass-
 photo matteShadow_zpsisgorqb9.jpg

So how do I get my MatteShadow Pass to have the quality of the Alpha manipulation method? I'm not seeing any options that would affect this in the render element pass options.

Any help would be greatly appreciated as this is sort of important. :D

Thanks in advance for any help/input guys.

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read 1599 times
10/26/2015 2:16:53 PM (last edit: 10/26/2015 2:16:53 PM)
show user profile  ScotlandDave
On first glance it looks like a linear/gamma issue.. Is the pass saved as a 32 bit format and/or if you apply a 0.454545 gamma correction to it ( ie the inverse of 2.2 - in photoshop do an Exposure adjustment and change gamma to 0.454545 ) does it look like the one in the Alpha version?

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read 1567 times
10/26/2015 11:08:30 PM (last edit: 10/26/2015 11:08:30 PM)
show user profile  herfst1
I think it's a threshold thing maybe. Like for irradiance map if you turn the clr. threshold down it will produce a better ir map. Same with DMC noise threshold. So threshold is my guess. Maybe in the settings tab you can turn the adaptive threshold down?

Of course I'm just stabbing in the dark, but it's worth a shot.
read 1557 times
10/27/2015 12:01:03 AM (last edit: 10/27/2015 12:01:03 AM)
show user profile  9krausec
Weirdly enough, it's none of those... Apparently these passes (alpha and matte shadows are calculated differently).

I was using progressive render mode and the alpha resolved far quicker than the matte shadow pass. After pissing away an hour I decided to let it run for a while and the layers then matched.

So totally my bad... However, I'd like to open up a discussion on what the best way would be to get the base shadows by themselves out of a render?

So far what I'm doing is rendering out a matte shadow pass, alpha masking my primary beauty comp, inverting the matte shadow pass, playing with some PS layer blending options and just sticking it at the bottom of the comp.. It "works", but I feel there probably is more of an elegant way to go about it...

GOAL: Get the ground shadows of the object rendered in a single pass that would work with transparency (separate from the hero object). Everything rendered out with one render (so it needs to be a pass).

Cheers for the replies though. GO TEAM GO!

- Portfolio-

read 1554 times
10/27/2015 1:02:01 AM (last edit: 10/27/2015 1:02:01 AM)
show user profile  donvella
use a pass manager...

right click > vray properties >

tick matte object, affect alpha, direct light, shadows

ta da

read 1540 times
10/27/2015 10:17:55 AM (last edit: 10/27/2015 10:17:55 AM)
show user profile  9krausec
I want a clean alpha unadulterated by the shadowa. I'm already using vary object properties to make the ground plane a matte object.

Thanks for the reply though.

- Portfolio-

read 1530 times
10/27/2015 12:22:19 PM (last edit: 10/27/2015 12:22:19 PM)
show user profile  donvella
isnt that what the direct light/shadow option is for?

read 1518 times
10/27/2015 10:50:01 PM (last edit: 10/27/2015 10:50:01 PM)
show user profile  9krausec
Not following. Educate me please.

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read 1514 times
10/27/2015 11:07:31 PM (last edit: 10/27/2015 11:07:31 PM)
show user profile  donvella

try this on your floor object, it should give u the shadow only with transparency. If i understand you correctly.

read 1507 times
10/28/2015 1:44:32 AM (last edit: 10/28/2015 1:44:32 AM)
show user profile  9krausec
Yeah. That's what I was doing and it messes up the alpha (shadows get put with the alpha).

Trying to figure out the optimal way to get ground shadows completely separate from object without affecting alpha.

I'll post up what I'm doing now tomorrow.


- Portfolio-

read 1503 times
10/28/2015 4:21:29 AM (last edit: 10/28/2015 4:21:29 AM)
show user profile  donvella
uncheck shadows in the direct light option. do it as 2 separate passes

Edit. Why dont u use vray shadow element?

read 1497 times
10/28/2015 5:10:22 AM (last edit: 10/28/2015 9:03:01 AM)
show user profile  9krausec
Jokes on me! I don't have the direct light option for Maya/Vray...

 photo 2015-10-23 11_35_34-Hypershade_zpsrtkoz78g.jpg

When unchecking shadows (of the floor vray object properties just to clarify) I get this-
 photo unticShad_zpsg9mzniiz.jpg

when I keep shadows on and turn off "affect Alpha" I get this (what I have been doing) -
 photo ticShadNoAlpha_zpstkdmjdey.jpg

I then use the MatteShadow pass as a mask under my beauty to get this-
 photo shadowComp_zpszlse03dz.jpg

I'm making sure this is the most optimal way to get the shadows separate whilst not affecting the alpha.

- Portfolio-

read 1477 times
10/28/2015 2:48:52 PM (last edit: 10/28/2015 2:48:52 PM)
show user profile  sheheryar_noor
i think austris have explained it here
read 1459 times
10/28/2015 8:07:25 PM (last edit: 10/28/2015 8:07:25 PM)
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