* How to use your GRASP surface files in Pov4Grasp
* How to build a GRASP molecular surface of "good quality"
* How to properly combine GRASP surface files and non-surface objects
How to use your GRASP surface files in Pov4Grasp
It's quite simple !
In this tutorial I will describe the main useful features of
this patch version of POV-Ray from the most simple case to some more
"complicated" effects that you can achieve. The
GRASP surface file that is
used here has been built from the X-ray structure of the small
Crambin protein. Three different surface
properties were calculated and written in the file : electrostatic potentials,
surface curvatures, and discrete colors enhancing several residues.
The GRASP file has been written without any transformation or
rotations. As the crambin structure coordinates are not centered at the origin,
the surface is not centered by default, so we apply a simple translation
within the script. Actually this translation uses a macro that allows to
keep exactly the same orientation due to the perspective. This macro is called
correct_translate in the different exemples, and is defined in the
common scene file scene.inc. The latter is
an include file which also defines a few global variables. Among them you
will find the SYSTEM variable which specify the coordinates system
that we use. The following scale <1,1,-SYSTEM> command in the
examples insure that the GRASP surface file will always be in the correct
coordinates system (GRASP uses a right-handed system while both systems can
be used within POV-Ray). Anyway all these stuffs are not really complicated
and most of the things are explained in the scene file.
Part 1: Getting started
- Our first trial
- Let's add some finishes
- Adding (multi-layered) textures
Part 2: Surface properties
- Mapping a surface property
- Changing the property range
- Setting the surface transparency
- Correcting projected shadows
- Adjusting the property colors
Part 3: Discrete colors
- Discrete colors on the surface
- Setting a global transparency
- Reading a color description file
Part 4: Template surfaces
- Object copying
- The power of template surfaces
How to build a GRASP molecular surface of "good quality"
This tutorial will actually adress several issues on how to get better pictures
of your GRASP surfaces. The idea is to produce molecular surfaces with a lot
of triangles in order to get smoother shapes, better colors and textures, and
to reduce the possible artifacts (incorrectly assimilated to "holes") produced
when projecting shadows on it.
Good quality surfaces
- What is "good quality" for a GRASP
molecular surface ?
- Is GRASP able to produce such huge
- Which parameter mostly affects
the number of triangles ?