Useful VMD-L Mailing List Threads
Transparency rendering by Tachyon
Hi, If you want the interior brighter, your easiest options include increasing the AO ambient and AO direct scaling factors, or choosing colors that are brighter to begin with (e.g. "pastel" or "washed out" colors that have a high white content and a relatively low to moderate amount of color saturation).
The glowlights script is sort of an expert-level means of placing positional lights in a specific part of a molecular structure so that you can add more targeted lighting. The glow lights are omnidirectional, but to make them useful for this purpose, they have distance-based attenuation equation that has constant, linear, and quadratic terms that you specify when the light is defined. By defining a light that has significant quadratic attenuation, you can make its effect highly localized, which is not something that you could do with either the normal VMD directional lights, nor the AO lighting. The current limitation with these glow lights is that to be useful to an end user, they have to be specified in model coordinates (e.g. cartesian coords of the molecular structure), but VMD and Tachyon have to use the lights in world coordinates, so there's some complex machinery involved in sorting out their coordinates, and at the moment this machinery is not part of the core of VMD, so to use them effectively requires more VMD scripting than I would like.
My plan is that I will soon be moving the logic for the glowlights into the core of VMD itself, and that it will be implemented both in the interactive OpenGL code path as well as the ray tracing engines such as Tachyon, so the effects of the glowlights can be interactively viewed, tweaked, and so on, and they could be used just as easily in a live demo as in a batch movie rendering. The catch is that while there's no limit on the number of such lights one could use in something like Tachyon, there are significant limitations on how well this works in OpenGL, and I will have to work through a minefield of driver bugs as I push VMD's OpenGL GLSL shaders further into areas where some vendor's drivers have had problems in the past. That said, I'm hoping that the drivers have all gotten significantly better, and that many of these past driver bugs are now "water under the bridge" as they say.
Cheers, John Stone vmd@ks.uiuc.edu
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