Below ascii art shows expected pattern of slots and times for MAXREC 5
//
//
// |
// |
// t
// | 3
// | 4
// | 2 3
// | 1 2
// | 0 2 1 1
// | 1 0 0 0
// +-----------------0--------> slot ------------------------------------->
// |
// | 4 3 4 2 3 4 1 2 3 4
// |
//
//
Choices over what to do with the pair:
Cannot form a line with only one valid point ? unless conjure a constant direction. The only hope is that a prior “thread” got the valid point as the second of a pair.
Perhaps that means must draw with GL_LINE_STRIP rather than GL_LINES in order that the geometry shader sees each vertex twice (?) YES : SEEMS SO
Hmm how to select single photons/steps ?
Storing photon identifies occupies ~22 bits at least (1 << 22)/1e6 ~ 4.19
Step identifiers
https://www.opengl.org/sdk/docs/man/html/gl_VertexID.xhtml
non-indexed: it is the effective index of the current vertex (number of vertices processed + first value) indexed: index used to fetch this vertex from the buffer
Geometry Shader Background