From: Axel Kohlmeyer (
Date: Mon Nov 15 2010 - 16:48:25 CST

On Mon, 2010-11-15 at 13:45 -0800, quantrum75 wrote:
> Hi there,
> I have a different question than the previous one. I am trying to
> render images using tachyon image renderer. However, my image has a
> gradient in the background. When I render the image, the resulting
> image is completely black without any gradient. How can I produce
> rendered images which have a background gradient?
> Thanks
> Rama

the background image is a special OpenGL output feature,
that is not easy to export to ray tracing.

the best you can do is to do a bluescreen/greenscreen trick.
i.e. render with a background color that does not appear
in your visualization and then use gimp or photoshop to
cut this away to transparency. and then generate the
background gradient with those packages and add it.

you have to be careful with antialiasing, as there will
be some "bleeding" at the edges, so a background color
that is similar to your intended background helps, and
also rendering at a (much) higher resolution.


Dr. Axel Kohlmeyer
Institute for Computational Molecular Science
Temple University, Philadelphia PA, USA.