[REQ] Shadow Catcher material...

zeitmeister · Post by **zeitmeister** » Thu Feb 28, 2013 1:47 am

Hey Ono,
just coming up again with an old request...

Zom-B · Post by **Zom-B** » Thu Feb 28, 2013 1:48 am

Now maybe even easier to realize since we have some proper alpha rendering mode?!

Post by **OnoSendai** » Thu Feb 28, 2013 2:11 am

How is this shadow catcher hack supposed to work again?

vis4arch · Post by **vis4arch** » Thu Feb 28, 2013 2:27 am

+1

Best for photo montage renderings.

Zom-B · Post by **Zom-B** » Thu Feb 28, 2013 2:27 am

It should be a tag or material for a (free to define) ground mesh that only gets "colored" by shadow rays.
Actually its the renderpass "shadows" for that object only or so...

zeitmeister · Post by **zeitmeister** » Thu Feb 28, 2013 2:45 am

galinette · Post by **galinette** » Thu Feb 28, 2013 4:28 am

OnoSendai wrote:How is this shadow catcher hack supposed to work again?

This would be a full shadow pass mode associated with a shadow material.

If the second eye vertex (first being camera) is not hitting a shadow material -> render white
If this is a shadow material -> render the resulting radiance divided by shadow material albedo.

Etienne

Post by **OnoSendai** » Thu Feb 28, 2013 4:40 am

galinette wrote:
OnoSendai wrote:How is this shadow catcher hack supposed to work again?
This would be a full shadow pass mode associated with a shadow material.

If the second eye vertex (first being camera) is not hitting a shadow material -> render white
If this is a shadow material -> render the resulting radiance divided by shadow material albedo.

Etienne

That could work somewhat. Would only really make sense for Lambertian shadow material.
Also I don't know if the workflow is good as you would have to render out a separate shadow pass and composite together.

galinette · Post by **galinette** » Thu Feb 28, 2013 6:31 am

OnoSendai wrote:That could work somewhat. Would only really make sense for Lambertian shadow material.

Yup, forgot to tell that

OnoSendai wrote:Also I don't know if the workflow is good as you would have to render out a separate shadow pass and composite together.

I thought this was the request. There are other 1-pass solutions with envmaps, but it's very impratical for unbiased renderers.

Post by **OnoSendai** » Thu Feb 28, 2013 6:32 am

galinette wrote:
OnoSendai wrote:That could work somewhat. Would only really make sense for Lambertian shadow material.
Yup, forgot to tell that
OnoSendai wrote:Also I don't know if the workflow is good as you would have to render out a separate shadow pass and composite together.
I thought this was the request. There are other 1-pass solutions with envmaps, but it's very impratical for unbiased renderers.

I will try an approach something like this. Basically I will define the 'unshadow fraction' to be something like reflected occluded luminance divided by reflected unoccluded luminance.

Post by **OnoSendai** » Thu Feb 28, 2013 6:50 am

teapot under Uffizi probe

zeitmeister · Post by **zeitmeister** » Thu Feb 28, 2013 6:50 am

It would be great as a pass, for sure.
But it would also help a lot as a shader!
Imagine just placing your model in front of a backplate and assign that shadow material to a floor... ready.
I really would appreciate that option!

Post by **OnoSendai** » Thu Feb 28, 2013 7:13 am

zeitmeister wrote:It would be great as a pass, for sure.
But it would also help a lot as a shader!
Imagine just placing your model in front of a backplate and assign that shadow material to a floor... ready.
I really would appreciate that option!

Why did you have to wait until I implement it the other way before you say how you want it? sigh.

Zom-B · Post by **Zom-B** » Thu Feb 28, 2013 7:34 am

OnoSendai wrote:Why did you have to wait until I implement it the other way before you say how you want it? sigh.

Just because you are so fast and nobody expected to see some results within days ^^
Another big benefit would be Background replacement via a HiRez image to be done directly in Indigo for fast composition, without doing 1001 renderings in Indigo and putting stuff together in PS...

Post by **OnoSendai** » Thu Feb 28, 2013 7:36 am

Zom-B wrote:
OnoSendai wrote: Another big benefit would be Background replacement via a HiRez image to be done directly in Indigo for fast composition, without doing 1001 renderings in Indigo and putting stuff together in PS...

This can be done with a background plate in the scene directly right?