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1.7.1 Shadow Channel Bug w/ Skydome

Posted: Tue Sep 16, 2008 1:39 am
by richardfollett
I am sorry if you think this has already been covered but I still dont get it!

I want to create my final render on a pure white background with shadow. So I create an alpha channel which I understand and I also create the shadow channel, now I want to merge them so end result looks like one of Hyltom renderers ;)

I am just trying to understand the workflow..

I know this is more a photoshop issue but I am sure someone understands what I am trying to achieve..

Thanks

Rich
Image

Posted: Tue Sep 16, 2008 8:33 am
by bjorn.syse
Well, in short, in photoshop:

1. Use the alpha-channel to "Mask away" the background from your render. So that you get a transparent background. You can use a specific actions made by Tom for this (available on the think.maxwelllrender.com site)

2. Now, place a layer beneath the render with transparent render, and fill it with white.

3. Third, use the shadow pass and place that on a third layer between the two first layers and set it's blending mode to "Multiply"

Hope that helps

- Björn

Posted: Tue Sep 16, 2008 10:03 am
by richardfollett
Thanks Bjorn,
Im loving that Action from Tom.

Cheers

Rich

Posted: Tue Sep 16, 2008 12:45 pm
by bjorn.syse
You're welcome. Yes that actions really is neat! How did it turn out?

- Björn

Posted: Wed Dec 03, 2008 6:02 pm
by richardfollett
Sorry to bring this up again but im lost.
I am trying to create a shadow channel but it is all white? Now it not all white to start with as I watch the file being created. Simple test with ball on a floor. I have set the floor material to except shadows. Any clues?

Thanks

Rich

So it look like this for about 1 SL then all white????
Image

Posted: Wed Dec 03, 2008 11:52 pm
by tom
How does the light source look like?

Posted: Thu Dec 04, 2008 4:56 am
by richardfollett
?? Light Source? Sky Dome

Posted: Thu Dec 04, 2008 11:17 am
by tom
OK, could you please send me the scene? :)

Posted: Thu Dec 04, 2008 11:27 am
by richardfollett
So I have this : Render
Image

And this Alpha :
Image

So why is my shadow Pass not working??

Thanks

Rich

Posted: Thu Dec 04, 2008 12:00 pm
by tom
I confirm this is a bug when shadow channel is used with skydome. But at least there's an equivalent workaround. Please download white.hdr from the link below and replace skydome with Image Based Lighting.

http://www.divshare.com/download/5997654-571

Here's the correct result:
Image

Posted: Thu Dec 04, 2008 12:08 pm
by richardfollett
Thank you Tom,
Sorry I was not aware there was a bug with the Skydome & Shadow pass.

Regards

Richard

Posted: Thu Dec 04, 2008 12:12 pm
by tom
Me neither :) Thanks for reporting it! Let me know if the workaround is acceptable.

Posted: Thu Dec 04, 2008 12:30 pm
by richardfollett
Thanks tom,
look ok but in photoshop blending layers I get white at bottom, this might be me doing something stupid. I have set blending mode to multiply on both layers. This correct?

Ta

Image

Posted: Thu Dec 04, 2008 2:13 pm
by tom
Can you replace "Remove Black Matte" with "Defringe 1 pix" (Layer / Matting / Defringe) in the Photoshop Action? Maybe there's a problem with generation of alpha and we'll check this, too.

Posted: Tue Dec 16, 2008 11:45 am
by tennet
Hi,

I'm using Cinema and Maxwell. Is it possible to render the RGB, shadow and the alpha channel in one go? Or do you always need to render alpha and shadows separetely?

Also, if I use an HDR environment for lighting and I need the shadow channel rendered - is it correct to create an image emitter with the HDR-map and then project this image emitter onto a sphere, instead of the sky object within Cinema? How big should I make this sphere to simulate a sky object in that case? If I'm totally wrong, please point me in the right direction. :?

I'm pretty new to Maxwell, hope I make sense.. Thanks!

// tennet