GRASP Surface File

A GRASP Surface File starts with five "lines" of eighty characters. The first line contains a format specifier, i.e. the words "format=1". (There are no other formats at this time.)

The second and third lines contain key words for the information contained within, i.e. "vertices" for the vertex positions, "accessible" for the associated accessible surface point coordinates, "normals" for the normal vector (of length unity) for each vertex, "triangles" for the triangle index list. The latter is a list of integers such that entries i-2, i-1 and i, where mod(i,3)=0, give the which vertices make up triangle i/3. NOTE that the index integers for the triangles are INTEGER*2 !

Line three contains which variable are also written to this file, "potentials", "curvature", "distances", "gproperty1", "gproperty2" being the key words for the appropriate quantities.

Line four contains the number of vertices, the number of triangles, the grid size of the lattice used to create it (i.e. the number of points along one edge of the cube, always =65), and the reciprocal lattice spacing.

Line five contains the midpoint of the coordinate system from which the vertices were derived (i.e. the midpoint of the Grasp box).

The data then follows in the order of the keywords. Note that all are REAL*4 except for the triangle indexes which are INTEGER*2.

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Last revised on 14 November 2009.