Haha you should write one then you can help me make mine better
Anyway I have been messing about with it for a while but still cannot draw outside the 0->1 range. I found this source online
https://github.com/kamend/3D-Metaballs-with-Marching-Cubes/tree/master/src (Note its not mine) to try and see how they control range and I see it uses gridX gridY gridZ which is basically the same thing as my m_volume_depth etc...
Can anyone have a look through that source and see which bit alters range so I can draw more than a unit cube.
Well I don't have time to look into it right now (gotta go in five minutes) but reading your original post's code again, you are normalizing your i, j, k counters so that they always fall in (-0.5 .. 0.5), and are always evaluating the metaballs there (so increasing volume_width and so on only increases resolution but not range). A quick fix is to keep the code the same, but multiply your x, y, z values by some factor like "scale". Then scale = 2 would render in (-1.. 1), scale = 4 between (-2..2) and so on. Try it and see if that works.