shadow pass and Nuke

[nomads]

Hi

I am comping objects onto a back plate in nuke.

What is the preferd way of rendering the shadow pass?

In Nuke I am using a grade node to colour correct the backplate using the shadow pass.

The image from vray comes with an alpha containing shadow information. This affects the back plate. Should I re render without the shadow info in the alpha? And just use the shadow pass info?


Also should you colour correct the shadow on the back plate differently than the shadow on the 3d object?

[Morbid Angel]

typically what you do is render the main cg without ground shadow, then render few shadow layers like direct and indirect shadow as well as occlusion (contact shadow) you can grade the plate based on that (this is old school way) or there is another way to use expression in nuke to apply proper gi bleed to the plate but compers often don't like that.

[nomads]

Hi Dmitry,

Thanks for getting back to me again.

Is there a way through Vray render passes to get all the information in one render?

Can you also tell me what this Nuke expression thing is?

N

[Morbid Angel]

I'll get back to you about the expression.

For the rest of the stuff you need to split the render job into two layers - one main beauty, second its shadow. For the shadow layer you can have vrayShadow, and vrayExtratex withe occlusion map in it which will emulate the contact shadow. This should be all you need.

[Morbid Angel]

Here is nuke script below, you need to render to separate channels for this one not multichannel exr as it produces monochrome alpha.


#! C:/Program Files/Nuke7.0v6/Nuke7.0.exe -nx
version 7.0 v6
define_window_layout_xml {<?xml version="1.0" encoding="UTF-8"?>
<layout version="1.0">
<window x="0" y="0" w="1936" h="1050" screen="0">
<splitter orientation="1">
<split size="0"/>
<dock id="" hideTitles="1" activePageId="Toolbar.1">
<page id="Toolbar.1"/>
</dock>
<split size="1916"/>
<splitter orientation="2">
<split size="804"/>
<dock id="" activePageId="Viewer.1">
<page id="Viewer.1"/>
</dock>
<split size="181"/>
<dock id="" activePageId="DAG.1">
<page id="DAG.1"/>
<page id="Curve Editor.1"/>
<page id="DopeSheet.1"/>
</dock>
</splitter>
</splitter>
</window>
<window x="1920" y="0" w="734" h="1073" screen="1">
<splitter orientation="2">
<split size="1039"/>
<dock id="" activePageId="Properties.1">
<page id="Properties.1"/>
</dock>
</splitter>
</window>
</layout>
}
Root {
inputs 0
name "F:/work/diman/AD/shots/EVENT 04/nuke/rgb_alpha.nk"
frame 1031
first_frame 1001
last_frame 1608
lock_range true
format "2048 1556 0 0 2048 1556 1 2K_Super_35(full-ap)"
proxy_type scale
proxy_format "1024 778 0 0 1024 778 1 1K_Super_35(full-ap)"
}
Merge2 {
inputs 0
name Merge1
xpos 1500
ypos 311
}
Read {
inputs 0
format "1920 1080 0 0 1920 1080 1 HD"
first 1000
last 1607
origfirst 1000
origlast 1607
origset true
version 2
name colored_alpha
xpos 730
ypos -673
}
Dot {
name Dot1
xpos 758
ypos -412
}
Read {
inputs 0
format "1920 1080 0 0 1920 1080 1 HD"
first 1000
last 1607
origfirst 1000
origlast 1607
origset true
version 2
name beauty
xpos 510
ypos -673
}
add_layer {coloredAlpha coloredAlpha.r coloredAlpha.g coloredAlpha.b}
Copy {
inputs 2
from0 rgba.red
to0 coloredAlpha.r
from1 rgba.green
to1 coloredAlpha.g
from2 rgba.blue
to2 coloredAlpha.b
name Copy2
xpos 510
ypos -427
}
set N1b4225d0 [stack 0]
Read {
inputs 0
format "1920 1080 0 0 1920 1080 1 HD"
before black
last 608
after black
origlast 608
origset true
version 2
name plate
xpos 180
ypos -273
}
MergeExpression {
inputs 2
expr0 Ar+Br*(1-A.coloredAlpha.r)
expr1 Ag+Bg*(1-A.coloredAlpha.g)
expr2 Ab+Bb*(1-A.coloredAlpha.b)
channel3 {none none none -rgba.alpha}
name MergeExpression1
xpos 510
ypos -249
}
push $N1b4225d0
Viewer {
inputs 2
zoom_lock true
freezeGuiWhenPlayBack true
input_process false
name Viewer1
xpos -920
ypos 951
hide_input true
}

[jasonhuang1115]

Hi Dmitry,
I pasted the script in NukeX 8.0v5 and only got a Merge node in the Node Graph. Is it due to the content only working in your saved version of 7.0v6?

Thanks,
Jason

[nomads]

Thanks Dmitry for the expression.

I will need to examine it in nuke.

[Morbid Angel]

try copy the text and save it as a text document with .nk extension - this worked for me under nuke 8

[jasonhuang1115]

Thanks Dmitry. It works as saved as a .nk file in Nuke 8.