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SG_LIGHT(3)		     Library Functions Manual		     SG_LIGHT(3)

NAME
     SG_Light -- Agar-SG light source node

SYNOPSIS
     #include <agar/core.h>
     #include <agar/sg.h>

DESCRIPTION
     The  SG_Light  node  defines  a  light source in a SG(3) scene-graph.  Each
     light source is associated with a priority number, which  determines  which
     lights  are used in the rendering.  The number of lights supported for ren-
     dering is dependent on the renderer implementation.

INHERITANCE HIERARCHY
     AG_Object(3)-> SG_Node(3)-> SG_Light.

INITIALIZATION
     SG_Light * SG_LightNew(SG_Node *parent, const char *name)

     void SG_LightAmbient(SG_Light *lt, M_Color c)

     void SG_LightDiffuse(SG_Light *lt, M_Color c)

     void SG_LightSpecular(SG_Light *lt, M_Color c)

     void SG_LightSpot(SG_Light *lt, M_Real cutoff, M_Real  exponent,  M_Vector3
     dir)

     The  SG_LightNew() function allocates, initializes, and attaches a SG_Light
     object.

     The functions SG_LightAmbient(), SG_LightDiffuse()  and  SG_LightSpecular()
     configure the colors associated with the ambient, diffuse and specular com-
     ponents of the light source.

     SG_LightSpot() sets the spot parameters of the light source.  cutoff speci-
     fies  the	cutoff	angle in degrees, exponent specifies the light intensity
     (the higher the exponent, the more focused the light source; a value  of  0
     provides  uniform	distribution),	and dir is the direction vector.  If the
     cutoff angle is < 180 degrees, the light source is  directional,  otherwise
     it is treated as a point source and the direction vector is ignored.

INTERNAL WIDGET API
     void SG_LightSetup(SG_Light *lt, SG_View *sv)

     The  SG_LightSetup() function sets up the renderer states associated with a
     light, prior to rendering.  This  function  is  usually  invoked  from  the
     draw() operation of an SG_View(3) (or derived) widget, prior to rendering a
     scene.

STRUCTURE DATA
     For the SG_Light object:

     int pri		    Priority  of  light source when number of sources is
			    limited (0 = highest priority).

     M_Color ambient	    Ambient color component of source.

     M_Color diffuse	    Diffuse color component of source.

     M_Color specular	    Specular color component of source.

     M_Real spot_cutoff     Spotlight cutoff angle (or 180 for point source).

     M_Real spot_exponent   Spotlight intensity distribution.

     M_Vector3 spot_dir     Spotlight direction.

     M_Real Kc		    Constant light attenuation factor.

     M_Real Kl		    Linear light attenuation factor.

     M_Real Kq		    Quadratic light attenuation factor.

SEE ALSO
     M_Real(3), M_Vector(3), SG(3), SG_Intro(3), SG_Node(3), SG_View(3)

HISTORY
     The SG_Light node class first appeared in Agar 1.6.0.

Agar 1.7			December 21, 2022		     SG_LIGHT(3)

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