Raytracing with POV-Ray

The Persistence of Vision Raytracer (POV-Ray) is included with Chimera. POV-Ray images can be saved:

• with Save Image
• with the copy command
• when making movies

Chimera includes two light sources, key (dominant) and fill (secondary). Their directions and intensities can be adjusted in the Lighting tool and are propogated to POV-Ray for raytracing. By default, only the key light produces shiny highlights and shadows. Decreasing the key-to-fill ratio will decrease the contrast between shadows and unshadowed regions. Interactive shadowing in Chimera (the show shadows setting in Effects) can be used to preview where shadows will fall.

See also: exporting a scene, tips on preparing images

Using transparency or per-model clipping may increase rendering time significantly.

A raytraced image from POV-Ray may differ from the view in Chimera in several ways. Some differences are desirable, such as the presence of shadows. Others reflect current limitations of the POV-Ray format and/or its implementation in Chimera:

• colors may differ slightly
• shading along ribbons may be stairstepped; the supersmooth ribbon style is recommended to decrease this effect
• parts of objects cut away with the global clipping planes in Chimera will still be shown in the raytraced image (however, the effects of any per-model clipping will be included)
• light source directions but not colors are translated from Chimera
• although object shininess and brightness levels (but not specular color) are translated from Chimera, objects tend to appear shinier in the raytraced image (perhaps a desired effect)
• if depth cueing is used, the background of the raytraced image:
  • will not be transparent even if the transparent background option is turned on
  • will match the depth-cueing color even if the background is a different color in Chimera
• the following are omitted or otherwise not handled: silhouettes, selection highlighting, stereo, lenses, Volume Viewer transparent solid displays, and normals on dot and mesh surfaces
• max_trace_level is set to 10 to improve multi-level transparency, but this also increases time and memory requirements relative to lower levels [details at the POV-Ray site]