void flow(VoxelGrid volume) {
// get the value of the current voxel
float v = volume.getValue(this);
// check neighbouring voxels for difference
Vec3D from = volume.repelFromValue(this, 0, 1, 0.1f).limit(0.1f);
if (!from.isZeroVector()) {
lastSub += 1;
} else {
lastSub = 0;
}
addForce(from);
}
