-----------------------------------------------------------------------------

1d gradient function.

Moller and Trumbore's method

finds the closest particle to a view ray

returns 1.0 for x==0.0 (unlike glsl)

returns 1.0 for x==0.0 (unlike glsl)

returns 1.0 for x==0.0 (unlike glsl)

send any changes to flex (all buffers guaranteed to be unmapped here)

update any buffers (all guaranteed to be mapped here)

:param gripper_type: :param sphere_radius: :param init_pos: By default below the ground before the reset is called