Imported from the mailing list archives.

Comparing the gtk2+opengl rendering to the lesstif+xrender rendering, they do the same:

multiple silk objects in the same layer group (same side) combine without translucency, as in an 1 bit bitmap
different layer groups (e.g. top side silk and bottom side silk) are combined with translucency, causig the shading effect you showed

(The same happens with any other group as well, silk was just an example.)

The translucency between different groups will not happen with gtk2+gdk and lesstif-without-xrender.

controlling the translucency

When Keith Packard fixed up our gtk+gl earlier this year, he foreseen different translucency preferences by users, so he added a feature called layer alpha. It's a floating point number, between 0 and 1 in the conf tree, under appearance/layer_alpha ; the default value is 0.7 I think. As of r13749, the lesstif HID also supports this.

The simplest way to try it out is from the command line:

./pcb-rnd foo.lht -c appearance/layer_alpha=1

If you find the right value, you can put it in any of the config files the same way you did with the invis-color.

It is also possible to change it on the fly, using the following action:

conf(set, appearance/layer_alpha, 0.2)

If you are using the gtk+gl HID, it is possible t change this value from the preferences window (Config PoV tree, appearance, layer_alpha).