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  1. #1

    How to animate a section of mesh to slowly go transparent in cycles

    Hello,

    I am trying to render a character's arm such that a section of the arm skin gradually becomes transparent.
    I know about vertex groups but not much about cycles and the node editor.

    I was thinking that I would need to duplicate the skin material and apply the duplicate to that section, then figure out animated transparency for it with nodes.

    My questions are:
    Is this the best way to go about this?
    Will it mess the UV's up? (The character is a ManuelBastoniLab char)

    When I try to duplicate the material, the new material ( with appended .001 ) seems to overwrite the existing one, so basically how *do* I duplicate a material correctly?

    Thanks for reading.Click image for larger version. 

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  2. #2
    What you probably want to do instead is create a texture (like the skin texture) and paint in what you want to go transparent. Then use a mix node in cycles with that texture as the factor



  3. #3
    Ok thanks smilebags. Any idea how to do that? I'm not seeing the + under the texture tab anymore..
    Last edited by Alternicity; 08-Jun-17 at 13:07.



  4. #4
    Ok nevermind that last, I made a copy through the UV editor. Fiddling with it now.



  5. #5
    Click image for larger version. 

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ID:	488267 Ok created that texture - can someone tell me how to add it? I don't seem to be able to right now. Am I even in the right place inside blender?



  6. #6
    Member JA12's Avatar
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    Originally Posted by Alternicity View Post
    I was thinking that I would need to duplicate the skin material and apply the duplicate to that section, then figure out animated transparency for it with nodes.
    If you assign that new material to the mesh, yes, but Cycles doesn't mix materials like Blender render material nodes do, if you're used to those.
    Cycles also doesn't support texture node tree. All textures in it go to material nodes.

    Click image for larger version. 

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    Simplified version of https://blenderartists.org/forum/sho...=1#post2511102

    1. Material node tree
    2. Mixing diffuse and transparent shaders with mix shader node. Don't confuse mix shader node with mix rgb node. Mix shader only mixes shaders, mix rgb mixes colors, and shaders with green socket only connect to other green sockets without exceptions.

    The setup is simple, I just made it complicated. The framed part is a texture. You could replace that with an image texture if you wanted to, or you could animate the value on the mix shader without connecting a texture.

    What my texture does there is take the coordinates from an empty object, rotate and offset them so I can show the empty, and then create a greyscale gradient from top down. It then controls the factor of the shaders where 0 (black) is diffuse, 1 (white) is transparent, and values in between is a mix of the two. But, with the setup the position of the texture can be controlled with the empty in the viewport.

    3. If the model has many layers or light goes through many bounces before getting in the transparent bits, might need to increase transparency bounces in render settings

    Click image for larger version. 

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    If you want to use a texture but keep the texture in place, could animate the transparency by controlling the greyscale values. In this one I made the gradient very small with color ramp and then
    1. added a math node, changed it to multiply mode, enabled clamp, and
    2. added keyframes to the lower field.

    What this does is multiply the values on the gradient with the value in the lower field, and clamp keeps values in 0-1 range even if you multiply with values outside that. Multiplying white (1) with 0 gives 0 and the whole thing is visible. Multiplying black (0) part with 0.5 gives 0, and 1*0.5 = 0.5, the top part is half transparent.

    So when animated, one gets this
    Last edited by JA12; 19-Jun-17 at 11:43.
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