I’m trying to take save out a view to a transparent PNG image using -ViewCaptureToFile with the TransparentBackground=Yes option set. The object is a mesh that has its vertices colored: mesh_with_colored_verts2.3dm (78.3 KB). I’ve opened the image in GIMP and took a screenshot (chequerboard indicates transparent areas): .
Most of the mesh is blue-ish, which comes out ok in a normal screenshot: .
I’ve extracted RGBA along a line into a spreadsheet and plotted RGBA:
It appears that the alpha channel somehow follows the red one, although not completely. I would expect alpha to be 0 (i.e. fully transparent) outside of the mesh, but 255 (i.e opaque) where the mesh is. I can’t see why alpha would have any kind of gradient to it. Is this my misunderstanding of what TransparentBackground=Yes should do, or is this a bug?
I’ve confirmed that Alpha=0 for all vertices with a little Python script that created a dump of MeshVertexColors(). I’m using Rhino5, SR12 64-bit.
Thank you all for your time