# Lighting Molecular surfaces

## Overall Goal

We need to draw molecular **surfaces** with their associated chemical
properties (surface colorings) well. This means that we need "good"
lighting (that helps with the perception of surface shape) and very
efficient drawing. Efficiency is important because the lighting might
require multiple passes, and also we want to be able to display
"galleries" of surfaces.

Our initial experiments show that _ambient occlusion_ shading is
valuable for making the surfaces more comprehnsible.

We need to:
1. understand the performance of our current hardware and software
   for doing molecular surface graphics
2. gain an understanding of what methods are appropriate for lighting
   and for improving the performance
3. implement these methods within the testbed

## Subgoals

1. Do a performance evaluation of Greg's system - especially in the
   case of where multiple molecules are being drawn. 

   This is important because we need to decide if we have a
   performance problem and what steps to take. 

2. In the event that there is a performance issue, explore what
   kinds of level of detail methods, culling, or other tricks might be
   useful to make improvements.

3. Add some form of enhanced lighting model to the system. Probably
   one form of ambient occlusion shading, and maybe some kind of Light
   Collage thing.

   One aspect of this is to determine which of the methods are
   appropriate for the kinds of shapes we have and the system we're
   building (both visually and performance).

   I would be curious about computing the ambient occlusion lighting
   over a coarse mesh and only doing local lighting on the full mesh
   to get the details.

   A specific task here is to provide implementations of (at least)
   the two main known hardware accelerated ambient occlusion shaders
   (or some approximate global lighting thing)

4. Experiment with using "dramatic lighting" to highlight a region of
   the molecule while still allowing the viewer to get shape cues from
   shading and using color cues to convey other chemical properties.


## Readings
- Conveying shape and features with Image-Based relighting  
  Note: the methods in this paper may not apply so easily, but the
  principles are important since they explain what good lighting is.
- Light Collages (Greg can show you the "expanded" version that
  discusses shadowing).
- Ambient Occlusion chapter from GPU Gems II  
  Note: this is available on the web
- Other papers on hardware assisted ambient occlusion computation.  
  There are several - I just don't remember what they are.
- TexMol - the Texas, hardware assisted, molecular graphics system  
  Note: this system doesn't specialize in (or even consider?)
  surfaces, however, we might want to add its capabilities to our
  system.