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Paul Chisholm avatar image
Paul Chisholm asked ·

Shadow/matte material

With Mental Ray I could use a ground plane assigned with a matte/shadow material to render shadows under the model. I could save as a .png with transparency on and the HDRI would disappear from the background leaving the shadows coloured black. With Arnold the shadows aren't black, they are the same colour as the HDRI background. How can I make them black?

colorshadowmatteshdr
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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

shadow.zip

Hi Paul,

Here is the basic scene setup.

Let me know if something isn't clear. ;)


shadow.zip (39.7 KiB)
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Paul Chisholm answered ·

Hi Michiel,

That's what I needed. Thank you very much for your help.

Paul

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Paul Chisholm answered ·

Hi Michiel,

Looks promising. What's is your method?

Thanks

Paul

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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

Both solutions above are transparent, with shadow matte map.

The ambient occlusion shader is also with transparent shadows.


shadow.png (615.5 KiB)
shadow2.png (1017.0 KiB)
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Paul Chisholm answered ·

Thanks Michiel,

That doesn't do what I need. Your other post is closer (https://answers.arnoldrenderer.com/questions/4258/rendering-ambient-occlusion-shader-shadows-as-tran.html), but that isn't actually transparent. There's a white dot under the shadow. I'd that shadow to be see through so I can put the rendered image over a coloured background or similar (on a website for example). I can do this with MR easily with a standard matte/shadow/reflection material. It's very frustrating.

Paul

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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

Ah, I see. Try turning off cast shadows of the plane.


settings.jpg (200.1 KiB)
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Paul Chisholm answered ·

@Michiel Van Gasse

Thanks Michiel,

I do get the shadows I'm after with those two methods, but not the reflections. Either way I do it (HDRI in the environment or Skydome texture) if I have background colour checked then I get that colour reflecting in the model instead of the HDRI. If I have the scene background checked then I get the HDRI instead of the shadows.

See the two images below. I need to combine the reflections of matte1 with the shadows of matte2.

With Mental Ray the ground plane was visible in the reflections, but could be made invisible in the plane's object properties by disabling Visible to Reflection/Refraction and enabling Receive Shadows. That doesn't work with Arnold.

I appreciate your help.


Paul


matte1.jpg (98.3 KiB)
matte2.jpg (67.6 KiB)
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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

Depends how you light the scene with the hdri.

On the left is with the environment, the right with the skylight. (change to the red marked settings)


settings.jpg (89.7 KiB)
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Paul Chisholm answered ·

@Michiel Van Gasse

Thanks Michiel,

I'm using the shadow matte map in a map to material. How do I hide the HDRI from the render?

Paul

,

Thanks Michiel,

I'm using the shadow matte map in a map to material. How do I hide the HDRI from the render?

Paul

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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

Create a shadow matte map in a map to material.

Hide the hdri from rendering to only save out the a shadow on a transparent background.

Here is the more detailed explanation : https://support.solidangle.com/display/A5AF3DSUG/Shadow+Matte

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