public void Set_collision_on(bool mval)
{
m_collide = mval;
this.checkBox_collide.Checked = m_collide;
// ghost collision-related stuff if collision not enabled
this.numeric_friction.Enabled = mval;
this.numeric_rolling_friction.Enabled = mval;
this.numeric_spinning_friction.Enabled = mval;
this.numeric_restitution.Enabled = mval;
this.numeric_collision_margin.Enabled = mval;
this.numeric_collision_envelope.Enabled = mval;
this.comboBox_collision_family.Enabled = mval;
}