Transparency with custom preview

So I am using custom preview a lot (who likes red & green transparent stuff anyways?), but have hit 2 bugs/limitations.

1. If one geometry with a transparency is inside another object with transparency, then the transparency of the inner object is ignored and it is set to transparency 1 (see screenshot 1 & 2). If the outer object is hidden, then the inner object displays correctly (screenshot 3).

I dont get why this would happen, as it is quite likely not a technical limitation.

2. Transparency is ignored for edges. This kind of makes sense, but it would be nice to be able to specify something other than color for the edges, like line width, line color, line transparency and line pattern.

Well actually it would be nice if Grasshopper stuff can just be displayed the same way as stuff in Rhino. I am working only in GH, so baking is not a "solution".

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Replies to This Discussion

Permalink Reply by Andrew Heumann on January 9, 2015 at 11:24am

yup - this is a known limitation. I wouldn't expect anything to be done about it any time soon...

Permalink Reply by Ethan on April 21, 2015 at 6:59am

so there is no way to make the gh geometry, not transparent even with custom preview? i set the alpha to 255 and yet I still see the edges of objects showing through?

Permalink Reply by David Rutten on April 21, 2015 at 9:21am

There are 3 issues here.

Rhino does not support transparency for curves. Never has, maybe never will.

OpenGL (and presumably DirectX) do not support drawing things *behind* transparent objects already drawn. There are tricks for making it look better, primarily drawing all geometry from back to front, and drawing backfaces and frontfaces at different times. These tricks are not used in Grasshopper, which does not have a central repository of all preview geometry. There will be no changes in GH1 in this area, GH2 may perform better, we do not know yet.

Wires are drawn a little bit in front of meshes to prevent them from being occluded. You can disable z-buffer bumping via the rightmost canvas toolbar button. It may improve the preview quality in some cases.

Permalink Reply by David Rutten on April 21, 2015 at 9:25am

Incidentally, for problems associated with item #2, you can change the draw order of previews, thus forcing geometry inside other geometry to be drawn first. Select the components whose preview you do not see, press Ctrl+B to put these components to the bottom of the stack, and then press F5 to refresh the drawing list.

Permalink Reply by Ethan on April 21, 2015 at 11:55am

thanks David!

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