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Guest Q

Cast Shadow And Reflection Alpha

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Guest Q
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  • I want to be able to render an object with a cast shadow and reflection on the floor as an image, where the floor is not part of the image. So that I can paste it into a different scene and maintain the reflection and shadow. I am sure I can figure a workaround of some sort, but it seems like this is commonly done.

    I am thinking that I should probably use multipass and make a channel for the shadow and reflection. But the components it yields are more like adjustment layers set to screen for reflection and multiply for shadow.

    I was hoping for or expecting an alpha channel around the shadow and reflection. Am I missing something?

    Maybe a compositing tag with the appropriate settings?

    If there is better way to accomplish this I would appreciate any thoughts thanks.

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    Guest Q
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  • Ahh, I figured it out. Sorry about that. I guess I just wasn't thinking straight.

    Q

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    Guest maddog_uk_69
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  • Happens to everyone ;)

    I have been scratching my head over exactly the same problem for a while now, and getting exactly the same (wrong) results as you. Any chance you could post your technique?

    Thanks in advance!

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    Guest espen_oe
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  • I dont know if this is the same problem but:

    I'm tying to export with alpha, but this seems to be impossible since the shadows need a floor to be cast on. How can I get the alpha channel to include shadows?

    Thanks

    Espen

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    I dont know if this is the same problem but:

    I'm tying to export with alpha, but this seems to be impossible since the shadows need a floor to be cast on. How can I get the alpha channel to include shadows?

    Thanks

    Espen

    I think this is what you are looking for? <_<

    I made the sphere invisible so that only the shadow and reflection are visible in the render. So now there is an alpha for the shadow and reflection. 2 channels that you can manipulate in layers in photoshop.

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    Guest espen_oe
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  • Thanks for that... But I now can understand how to get my model/object to come along as an element....

    How does the background stay invisible but everything else is visible...?

    I'm really sorry I'm a bit thick, but I just cant get it to work...

    Thanks..

    Espen

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    Thanks for that... But I now can understand how to get my model/object to come along as an element....

    How does the background stay invisible but everything else is visible...?

    I'm really sorry I'm a bit thick, but I just cant get it to work...

    Thanks..

    Espen

    Not sure if I understand what you are trying to do? Do you want just the objects in your scene to show up with alphas?

    Are you simply trying to exclude the background and floor?

    Can you be a little more descriptive in want you are trying to accomplish? :D

    It's going to be hard to help you out if we can't figure out what you want. Maybe do a simple sketch of a scene and point to the only things that you want to keep. That might expedite things. B)

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    Guest hurtstosit
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  • Hello Everyone,

    I was looking for the solution to the dilemma above too.

    The final result I need is a PNG file that has my objects, and the reflections/shadows of those objects on the floor, but the floor itself needs to be transparent elsewhere.

    I poked at the various multi-channel output methods, but it still illudes me.

    Attached is a screenshot from Photoshop of the ideal result using the C4D sample file attached in this thread.

    -- Since the PNG goes into plain-old PowerPoint as an illustration, I won't have the benefit of using layer transfer methods, like screen/mulitply, in Powerpoint - the final result needs the pixels to be transparent, partially transparent, or opaque.

    Thanks in advance for your advice/help.

    Cheers,

    jamie

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    Guest Teap
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  • I also would like to know how to do this. Any help would be appreciated.

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    Guest icd
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  • Bringing this post back from the dead because this problem has plagued me for years.

    Any of you know how to render out a reflection pass with alpha (just the reflections and everything else transparent)?

    i mean srsly.

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    Guest Joshfilms
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  • Few different ways to achieve this. You could render a "reflection pass" separate then composite it in AE or you could setup a multipass render in C4D to AE.

    In C4D you would need to add a object buffer to the object in my case the cube. You would want to use a white material with a white in the color channel (100%) and luminance channel of around 35% (so you can see shadow on white) and a reflection in my case I used 38% for the reflection.

    Render out a rgba pass or just the cube movie with straight alpha and add a reflection multipass render.

    In AE. bring in your footage/picture > drop your rgba or .mov with alpha on the picture. It will be in my case a cube floating with a white floor and background. > then set its blending mode to multiply. This will leave your shadow and make the cube somewhat transparent. > Drop another instance of your rgba/.mov on top and use the object buffer so your cube is back to normal transparency. > drop your reflection multipass render above your footage > set blending mode to add. Adjust opacity to liking add a blur if you want.

    I would just create separate renders but this is a way to do it with one render. These are just 2 ways to do it off the top of my head. Maybe a video tutorial if I get some time.

    Picture of render in C4D before AE

    post-45611-1229500547_thumb.jpg

    Picture of comp in AE

    post-45611-1229500509_thumb.jpg

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    Guest icd
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  • Thanks so much! That was extremely helpful. I was using multi-pass before but had no idea which blending settings AE needed.

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