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Thread: Transaprency oddity

  1. #1

    Transaprency oddity

    Hello
    I'm encountering weird behavior with LW 2018 / 2019 transparency. I need to use a b/w gradient do fade off the visibility of several layers. But when I apply my B/W gradient alpha, the transparent zones are actually opaques, just not displaying the surface textures where there is transparency but the basic surface color. instead of transparency. I tweaked the ray recursion limits , refraction etc (the layers are just flat planes, no thickness). Also I'm using standard material, the layers are 100 % luminous and 0 % diffuse.
    I had the same issue when making large clouds geometry ([planes) with transparency around the cloud, still renders black or basic surface color under the texture.
    Never had this problem before LW 2018.
    I can't use clip map as there is a progressive contour to my alpha / transparency image.

  2. #2
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    Here is the problem

  3. #3
    Goes bump in the night RebelHill's Avatar
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    Gonna need more details or an example, I fear. From this is just looks like youve got your transparency gradient back to front.
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  4. #4
    Hello Greg!
    I'm doing a simple earth zoom out / zoom in scene. I have 12 layers textures with several images map from satellite photo with different zoom level, from close to far, with 1 millimeter distance between the planes. The camera moves up on the y axis, the layers are synchronized in size and position to align with the one below.
    The gradient is just a circular b/w image with progressive contour. I'm using standard shading model as I don't need any advanced shading for this. The transparency is correct, white = transparent, black = opaque. No GI, 0% diffuse, 100% luminosity.
    Oh, I just noticed that if I go in perspective view VPR shows everything correctly, all the mask are working 100% as expected, but when rendering the scene from the camera view THEN I get those weird problems. Is It a bug? How can It render properly in the perspective view and not in the camera's?
    Last edited by marchermitte; 05-22-2019 at 07:10 AM.

  5. #5
    Here are the alphas channels from the camera view and from the perspective (matching the cam location)

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  6. #6
    Goes bump in the night RebelHill's Avatar
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    Surely this is what Id expect... white transparent, black opaque... so the planes are transparent in the central oval, and opaque around the edges/frames...

    Though it showing it one way in perspective, but another from the camera view... that's odd. Is there a vpr shot from perspective so we can see what it's supposed to be showing?
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  7. #7
    Super Member kolby's Avatar
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    Don't know why but setting the Refraction Index to 1.0 or disabling Raytrace Refraction works as expected here.
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  8. #8
    As for the alpha layer, the white (of a rendered alpha channel, not the transparency gradient) is supposed to be the opaque part and the black the transparent so the transparency grad is correct.
    Here are 2 vpr, one form the persp and one form the cam

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    Click image for larger version. 

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    Might the problem come from really big distances and scales? The cam is at almost 40 km high at the end of the vertical elevation...

  9. #9
    Goes bump in the night RebelHill's Avatar
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    Yeah, taht is unusual. but yes, it might come from the extreme scale, esp given the camera distance relative to the plane separation of only 1mm... Perhaps try fiddling with the ray precision setting in render options, or jut space the planes further apart.
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  10. #10
    ok, I reduced the scale of all the layers to 5 % of the previous size + doubled the space between layers and It works fine now.
    Thank you for your help.

  11. #11
    Not so newbie member lardbros's Avatar
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    I wondered if draft mode was set in your VPR options... it reduces the ray recursion limits to 2 or something, which is good for speed, but obviously not for this kind of thing.
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