Want per-model silhouette edges

[andre@…]

On Mar 25, 2021, at 10:09 PM, Andre LB Ambrosio wrote:

Dear all,

I wonder if it's possible to display silhouettes selectively in the same figure; for instance, displaying silhouettes only on structure representation (around sticks, spheres, cartoons and so on), but not around the maps or volumes that surround them.
Many thanks in advance,

Andre

[Tom Goddard]

Begin forwarded message:

From: Tom Goddard
Subject: Re: [chimerax-users] Displaying silhouette around specific visual elements
Date: March 25, 2021 at 8:23:39 PM PDT
To: Andre LB Ambrosio
Cc: chimerax-users@…

Hi Andre,

It is not currently possible to display silhouettes on some models and not others.

Several people have wanted this but I think it is complex to achieve. The silhouettes show boundaries where the depth in the entire scene changes abruptly. In order to have per-model silhouettes the ChimeraX GPU shader programs would need to compute an additional depth buffer separately for each model. Also the silhouette edges are not currently drawn at a specific depth. If per-model silhouettes were supported a stick model with silhouettes beneath a transparent surface needs to draw the silhouettes under the transparent surface so knowing the depth of the silhouette edge becomes important. When not using silhouettes the shader programs need to not compute the extra per-model depth buffers otherwise it would slow down rendering even when not being used. Adding these additional complexities to already complex graphics rendering shader programs have so far made this feature out of reach for our one graphics rendering developer (me).

I made a feature request for per-model silhouette edges and perhaps in the future we will find a simpler way to implement it that makes it feasible.

​https://www.rbvi.ucsf.edu/trac/ChimeraX/ticket/4420

Tom

[Tom Goddard]

A couple older tickets want to turn off silhouettes specifically on mesh surfaces where they ruin the appearance making silhouettes unusable in combination with meshes. Ticket #2363, #2765