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Setup a Physical Moon Light
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A physical moon light can't exist without a physical sky light. So all starts with the creation of a physical sky light (:doc:`/tasks/ta_ca/ta_ca_light/tk_setup_a_physical_sky_light`).

Then the sky light is used to set up the moon light according to its sky model:

.. code:: cpp 

    // "sky" is a pointer to a previously created and set up RED sky light instance.
    RED::ISkyLightShape* isky = sky->As< RED::ISkyLightShape >();

    // Initialize the moon light according to the current sky model settings.
    RED::Object* sun = NULL;  // passing NULL makes the method below to create the sun instance for us.
    RC_TEST( isky->SetMoonLight( sun, iresmgr->GetState() ) );

Because the moon is a physical light, no other parameters are needed (like colour or intensity) and all other data are computed based on physics simulation.

.. note::

    The moon is a very weak source of light. Therefore, its contribution to a scene is often quite subtle. 