Fem: Partial transparency fix in FemPostObject display modes #12918
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marioalexis84
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Nice, I tested this and it's working properly. It's great to also get rid of the annoying red warning text about the recommended backlight usage. @chennes Can you merge this? |
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#6996 could be closed and replaced with an issue explaining why this pull request does not resolve the issue completely and also report the issue in the Coin repository. |
Right, it makes sense. Fortunately, the remaining issue is IMO really minor from the FEM postprocessing perspective. |
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This pull request is an attempt to fix #6996:
The transparency type used by the scene graph is
SORTED_OBJECT_SORTED_TRIANGLE_BLEND. This transparency mode works well with polygons using aSoMaterialwith multiple colors but does not handle points and lines correctly: In this mode with transparency enabled, lines and points are rendered using only the first color in the color array (current behavior) .According to the Coin documentation, these objects should be passed in the
SORTED_OBJECT_BLENDmode, but in order to be effectively drawn with transparency respecting the color array, it is necessary to enable this mode explicitly, for example, by using aSoTransparencyTypeobject within the shape separator.Doing that still doesn't work correctly because the order on the screen doesn't respect the z-value of the shape elements (the back lines and dots are rendered on top of the front objects seemingly randomly). (see figure 1).
The shapes are drawn in the correct order if the transparency mode is
BLEND(fig. 2), but the problem with this mode is that if there is another shape behind the transparent object, the background color is visible (fig. 3).To mitigate this issue, the buffer depth test is disabled if the object is completely transparent.
Another unreported issue is fixed with the first commit.
Currently it is necessary to activate the backlight to work with Fem Pipeline objects.
This occurs because the nodes of the Fem mesh are exported to the VTK array in wrong order (nodes of the SMSH elements do not respect the same order as the VTK cells points).
Sorting the nodes correctly fixes this problem and the backlight is no longer necessary.
fig1.
fig2.
fig3.