> Please help...
> Want to allow a user to interactively position/orient a volume rendering
> of the brain and hand-trace along sulci (cavities) of interest.
> Currently using 'volren' (SGI volumetric rendering code using texture
> mapping) to volume render a brain.
> I want to see the curvature of the brain's surface (cortex), yet when I
> set opacity high for the cortex, artifacts appear. These artifacts seem
> to occur where a portion of the brain's surface is nearly parallel to the
> view plane. Since the cortex is highly convoluted, nearly every portion
> of the brain displays some facet nearly parallel to the view plane and
> artifacts abound.
> Visually, these artifacts look like rings on a topographic map and if
> correct and stationary, they might actually guide a user's hand while
> tracing. However, because they shift and warp with varied viewing
> location, the reliability of each tracing becomes dependent on camera
> position and integrity is suspect.