Semi transparent object behind transparent window isn't visible.

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Semi transparent object behind transparent window isn't visible.

nophead
If I have a semi transparent object I can see objects behind it as long as I draw it later. I.e. I can see through it and the objects behind look lighter. If one of those objects is itself semitransparent it becomes invisible.

Is this a bug or just a limitation in the rendering operation?

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Re: Semi transparent object behind transparent window isn't visible.

MichaelAtOz
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See https://github.com/openscad/openscad/issues/310
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Re: Semi transparent object behind transparent window isn't visible.

nophead
I don't think it is that issue. The rendering order isn't the problem. The problem is the alpha blend applied twice doesn't look any different from it applied once.

On 16 August 2017 at 23:36, MichaelAtOz <[hidden email]> wrote:
See https://github.com/openscad/openscad/issues/310




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Re: Semi transparent object behind transparent window isn't visible.

MichaelAtOz
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a. > I can see through it and the objects behind look lighter. If one of those objects is itself semitransparent it becomes invisible.
b. > The problem is the alpha blend applied twice doesn't look any different from it applied once.

Umm, perhaps a concrete example may help.
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Re: Semi transparent object behind transparent window isn't visible.

nophead
I made a small example and found it only goes wrong if the transparency is created by the % operator. If it is made with the color module it works.

sphere(10);

translate([0, -20, 0])
    %cube([10, 2, 10], center = true);
       
translate([0, -50, 0])
    color("white", 0.5)
        cube([20, 2, 20], center = true);




If both transparencies are created with % then it works. So I think it is an order issue after all. It looks like the % operator trees are rendered later than the rest. That works if you don't have any other transparent objects but not if you have any made with color that are in front.


On 17 August 2017 at 22:44, MichaelAtOz <[hidden email]> wrote:
a. > I can see through it and the objects behind look lighter. If one of
those objects is itself semitransparent it becomes invisible.
b. > The problem is the alpha blend applied twice doesn't look any different
from it applied once.

Umm, perhaps a concrete example may help.



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