Raytracing with POV-Ray
The Persistence of Vision Raytracer (POV-Ray)
is included with Chimera. POV-Ray images can be saved:
Only the PNG (*.png) image format can be saved.
In addition to images, files for POV-Ray containing the scene (*.pov)
and the raytracing options (*.ini) may be generated.
Various raytracing parameters can be set in the
Chimera includes two light sources,
key (dominant) and fill (secondary).
Their directions and intensities, which can be adjusted in the
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.
exporting a scene,
tips on preparing images
Using transparency or
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
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
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:
- the following are omitted or otherwise not handled:
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]
UCSF Computer Graphics Laboratory / June 2008