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Thread: Problem holding reflection in the alpha channel on a transparent plane

  1. #1

    Problem holding reflection in the alpha channel on a transparent plane

    I'm creating a logo which will have a reflection on a floor. The floor is a PS file and I'll comp the 3D logo anim over the 2D floor in AE.

    I've put a 100% transparent plane under the logo with a 15% reflection so I can have the reflection as part of the animation. I'm getting the look I want in LW but when I render the file the alpha only shows the logo not the reflection.
    Can someone tell me what the proper setup is for my transparent plane so the reflected logo is retained in the alpha channel for compositing?

    Thanks
    DI
    Time is not linear but rather an eternal "now."

  2. #2
    More Liquid than Solid SquishyAni's Avatar
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    Hmmm... One option that you could do is just copy the model, and flip the Y value of its Size to *-1. Then render separately and composite. There might be an easier way, but that is beyond my knowledge as of now. Anyone else know?

  3. #3
    I think it would work if you did a pass using an alpha of the logo on the transparency channel of the plane and making sure in Advanced it is set to "Surface Opacity". This should give you the logo in the alpha pass. If I understand you correctly.

    EDIT : Sorry. Spoke too soon.Now I get what you wanted. But there is a way. I am sure of it.
    Last edited by Surrealist.; 06-25-2013 at 07:21 PM.

  4. #4
    skeptic lertola2's Avatar
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    I think your workflow should be like this: Render your scene with a black background so your reflection is in front of black. In aftereffects make two copies of this render. In one copy disable the alpha channel and find the rendering mode that mixes your reflections best with your background. It could be hard light, soft light, overlay or screen. Put the other copy of the render on top with the alpha channel intact.

  5. #5
    it's a manhole cover ↓ JoePoe's Avatar
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    If you are "getting the look your after in LW" why not just project the PS on the ground and render out and be done?? I'm sure there is a reason.

    So.... Isn't this a job for render buffers? PSD Export or Buffer Export or any of the other plugs out there. You would have a separate image sequence just for the reflection. And then, do what lertola said, run it through in AE with a blend

    That being said... I'm up for a challenge.
    Alpha channels respect geometry and transparency right? So in order to get the reflection to show up in Alpha I used a shader > reflection node > invert > into transparency on the ground plane.
    I don't know it it's actually 100% (or even 10% ) doing the right thing.... but it looks like it might be close.

    (edit: hmmmm, shadow is missing in the alpha. Is that always the case?)
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    Last edited by JoePoe; 06-25-2013 at 09:40 PM.
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  6. #6
    it's a manhole cover ↓ JoePoe's Avatar
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    Amazing what looking away for a bit can do.

    Still not exactly sure how you would use this but....
    Alpha with reflect & WITH shadow.. and blur too.
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  7. #7

    Not to offend but...

    Quote Originally Posted by SquishyAni View Post
    Hmmm... One option that you could do is just copy the model, and flip the Y value of its Size to *-1. Then render separately and composite. There might be an easier way, but that is beyond my knowledge as of now. Anyone else know?
    Yeah that's pretty old school. I did that back in the early 80s with the Alias Wavefront system when I needed a river boat reflecting in the water. Not that the system couldn't do it I just didn't know how. Electric Image has the best RGB to Alpha output I've ever seen for glass and transparency (worth a look). It actually over fills the RGB channel so once keyed with the alpha it looks like the original render. I've never seen another app be able to do that. LW isn't real good if you want to composite glass over a background (at least without a bunch of gymnastics).

    Appreciate the suggestion though. Thanks
    DI
    Time is not linear but rather an eternal "now."

  8. #8
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    Please don't take offense LW Community. I find it almost comical listening to all these solutions for the simplest type of request. Every other 3D app I've ever used simply gives you the appropriate alpha channel for what was rendered except LightWave. I've attached my rendered frame, the alpha and a comp rendered inside the app.

    The alpha which for whatever reason just doesn't include the reflection boggles my mind. I've thrown in a comp that was rendered in LW with the background image to show what I want to get once composited This is an animation not a still so for those of you who are saying "why not comp it in LW" - there are reasons.

    This should be the simplest thing in the world without having to create complex nodes or inverse and re render my geometry. Heck a little 3D app called Infini-D back in the 80's written by a bunch of students at U Mass could output a proper alpha with version 1.0 of their software. I just find it hard to believe something like LW doesn't do this (can't beat the LW modeler though).

    Sorry to rant but this should be a no brainer and every time I need to do something with a reflection or glass this becomes a major hurdle.

    Anyway JoePoe you have the best solution I can see for this but the software should still just give you an alpha with the transparency included and the RGB bold enough that when keyed, the final composite looks like the render and that is just never the case.

    Thank to all who chimed in.
    DI
    Time is not linear but rather an eternal "now."

  9. #9
    Why do you need an alpha channel when you can simply export the reflection pass? A reflection pass would give you more control I would think as well.

  10. #10
    it's a manhole cover ↓ JoePoe's Avatar
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    What a PAYNE! (sorry, I couldn't resist).

    But seriously, like I stated above, I'm not sure why you want it this way. Why combine the object (logo) and reflection into one... alpha??
    Doesn't this contradict the purpose of compositing in the first place? You want individual control in AE. In the ideal situation you want separate sequences for everything you want to comp.... diffuse, spec, reflec, trans, etc etc (on a per object level even).... everything. AND you should only have Alphas for objects and transparency. You don't want an alpha for reflection because you don't want certain parts of the reflection to be more/less transparent than others.... do you??? Why? I would think you want to bring in the reflection pass (by itself) and comp it in with a blend... like screen or multiply or whatever. It shouldn't have different transparency levels.... that's going to look.... odd (unless ypour going after some very specific stylized visual approach).

    And this is exactly what the render buffers do. With one click.

    Last edited by JoePoe; 06-26-2013 at 10:07 AM.
    System Specs: A pile of sand, a couple of wires, a real live mouse and a beer.

  11. #11
    Quote Originally Posted by Surrealist. View Post
    Why do you need an alpha channel when you can simply export the reflection pass? A reflection pass would give you more control I would think as well.
    I'm all ears. I wasn't even aware this was an option. I don't see anything about it in the manuals and have never heard it mentioned in any of the (thousands) of tuts I've found. What's the process?

    Thanks!
    DI
    Time is not linear but rather an eternal "now."

  12. #12
    Quote Originally Posted by JoePoe View Post
    What a PAYNE! (sorry, I couldn't resist).

    But seriously, like I stated above, I'm not sure why you want it this way. Why combine the object (logo) and reflection into one... alpha??
    Doesn't this contradict the purpose of compositing in the first place? You want individual control in AE. In the ideal situation you want separate sequences for everything you want to comp.... diffuse, spec, reflec, trans, etc etc .... everything. AND you should only have Alphas for objects and transparency. You don't want an alpha for reflection because you don't want certain parts of the reflection to be more/less transparent than others.... do you??? Why? I would think you want to bring in the reflection pass (by itself) and comp it in with a blend... like screen or multiply or whatever. It shouldn't have different transparency levels.... that's going to look.... odd (unless ypour going after some very specific stylized visual approach).

    And this is exactly what the render buffers do. With one click.

    JoePoe you kill me (What a Payne - HA!) You've been in Boston too long (wink). No but you're totally right about the total control in the composite stage. I'd be totally happy to have an opaque reflection and work my magic in AE. I just am not familiar with the process for getting this. I tried your node config and didn't get anything different. Not sure what surface settings you had on your initial marble surface (a procedural I suspected) but I didn't get the reflection in the alpha.

    This is all fine if the method you and Surrealist are suggesting is the way to go. Is there any documentation on the process? A tut somewhere perhaps. I find the manual either assumes the user knows more or the app is just so deep it doesn't cover everything.

    Help!!!
    And Thanks guys.

    DI
    Time is not linear but rather an eternal "now."

  13. #13
    For the documentation look under Image Filters. Photoshop PSD Layer Export.

    Here is a well known one that I think was moved from the original location:

    http://www.db-w.com/products/exrtrad...uffers?start=8

    It is old and I am not sure it covers the PSD export.

    But PSD is an easy way to go and I believe you can import right into AE. So you have your beauty shadow, spec reflect, and all of that on layers. You can choose which ones you want.

    Anyways find the plug under Composting Options Image filters.

    Usually... from my understanding anyway....Alpha is used to composite objects, transparency and light glows ("Flare to Apha" Image Filter). And everything else is composite layers.
    Last edited by Surrealist.; 06-26-2013 at 11:15 AM.

  14. #14
    it's a manhole cover ↓ JoePoe's Avatar
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    Yeah, it all depends on how "crazy" you want to get with control.

    For example (thanks for posting your image btw) you have the reflection in the logo and the reflection on the ground.
    The lazy way, of course, is to just render out the object(s) with that as part of it...... no control.
    OR you can render out a Global reflection pass. One that contains both/all reflections. But any changes done in AE would obviously change both object and floor reflections.
    Or separate reflection passes for separate objects. And on and on and on... with other channels as well.
    (side note: if you look at articles or vids on serious hollywood compositing they can have dozens and dozens and DOZENS of passes.... that would drive me nuts.)

    So, if you want one basic simple pass you can use Image processing > Render Buffer Export.
    More passes use Image processing > PSD Export.

    For multiple objects/multiple passes there is Passport. Here is a vid showing it being used to send passes to Blender, but the export part should be the same regardless.

    AND also Image processing > DP_Filter Node Editors (part of Denis' collection)..... tutorial and another (welcome to Thunderdome!! )
    Last edited by JoePoe; 06-26-2013 at 02:02 PM.
    System Specs: A pile of sand, a couple of wires, a real live mouse and a beer.

  15. #15

    Thank You!

    Quote Originally Posted by Surrealist. View Post
    For the documentation look under Image Filters. Photoshop PSD Layer Export.

    Here is a well known one that I think was moved from the original location:

    http://www.db-w.com/products/exrtrad...uffers?start=8

    It is old and I am not sure it covers the PSD export.

    But PSD is an easy way to go and I believe you can import right into AE. So you have your beauty shadow, spec reflect, and all of that on layers. You can choose which ones you want.

    Anyways find the plug under Composting Options Image filters.

    Usually... from my understanding anyway....Alpha is used to composite objects, transparency and light glows ("Flare to Apha" Image Filter). And everything else is composite layers.
    Thanks so much. With your help and that of JoePoe I hope to solve this issue. Amazing work btw, couldn't help but look you up.

    DI
    Time is not linear but rather an eternal "now."

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