Metaball rendering question

le4hoa

Hi all,

Sorry for my silly question but I recently need to implement some sort of merging spheres and ran across Andreas Jonsson's article about metaballs rendering (http://www.angelcode.com/dev/metaballs/metaballs.asp). This looks like what I need to do. However, after reading his article up and down I still don't understand how to map my spheres' coordinates (which is in world coordinates system) to the gridcell coordinates.

My sticking points are these:

1. If I want to merge 2 spheres (close by, intersected, or none at all), how many grid cells do I need?

2. How do I set the grid cell's coordinates to make sure they intersect the spheres' surfaces? Andreas Jonsson's code shows the method of ConvertWorldCoordinateToGridPoint() and ConvertGridPointToWorldCoordinate() but I don't know if these method would work in my case, which is more general.

Thanks so much for all your assistance.

Sincerely,
Van.