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, which can be adjusted in the Lighting tool, are propogated to POV-Ray for raytracing. By default, only the key light produces shiny highlights in Chimera and highlights and shadows in the raytraced result. Decreasing the key-to-fill ratio will decrease the contrast between shadows and unshadowed regions in raytraced images.

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 angstrom symbol (Å) in distance measurements causes a failure; this symbol can be turned off or the entire label hidden using the Distances tool
• the following are omitted or otherwise not handled: silhouette edges, 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]