lmbind(3G)							    lmbind(3G)

NAME    [Toc]    [Back]

     lmbind - selects a	new material, light source, or lighting	model

C SPECIFICATION    [Toc]    [Back]

     void lmbind(target, index)
     short target, index;

PARAMETERS    [Toc]    [Back]

     target  expects one of these symbolic constants:  MATERIAL, BACKMATERIAL,
	     LIGHT0, LIGHT1, LIGHT2, LIGHT3, LIGHT4, LIGHT5, LIGHT6, LIGHT7,
	     or	LMODEL.

     index    expects the name of a material (if target	is MATERIAL or
	      BACKMATERIAL), a light source (if	target is one of LIGHT0
	      through LIGHT7), or a lighting model (if target is LMODEL).
	      Name is the index	passed to lmdef	when the material, light
	      source, or lighting model	was defined.

DESCRIPTION    [Toc]    [Back]

     Lighting operation	is controlled by eleven	lighting resources, each of
     which has a symbolic constant as a	name.  lmbind binds a material,	light
     source, or	lighting model definition to one of these eleven lighting
     resources.	 Its first argument, target, takes the symbolic	name of	a
     lighting resource.	 Its second argument, index, takes the name of a
     lighting definition to be bound to	that resource.	index specifies	a
     material definition if target is MATERIAL or BACKMATERIAL,	a light	source
     definition	if target is LIGHT0 through LIGHT7, or a lighting model
     definition	if target is LMODEL.

     Two of these resources, MATERIAL and LMODEL, are special, in that they
     together determine	whether	lighting calculations are made or not.
     Lighting calculations are enabled when a material definition other	than
     material 0	is bound to MATERIAL, and a lighting model definition other
     than model	0 is bound to LMODEL.  When either MATERIAL is bound to
     material definition 0, or LMODEL is bound to lighting model definition 0,
     all lighting calculations are disabled.

     Thus, for example,	lighting is defined and	enabled	in the most primitive
     way by the	following code sequence:

	  lmdef(DEFMATERIAL,1,0,nullarray);
	  lmdef(DEFLMODEL,1,0,nullarray);
	  lmbind(MATERIAL,1);
	  lmbind(LMODEL,1);

     This primitive lighting model is disabled efficiently by simple binding
     material 0	to MATERIAL.

	  lmbind(MATERIAL,0);






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lmbind(3G)							    lmbind(3G)



     A lighting	definition is unbound from a lighting resource only when
     another definition	is bound to that resource.  Changes made to a lighting
     definition	while it is bound are effective	immediately.  By default all
     eleven lighting resources are bound to definition 0.  If lmbind is	passed
     a name that is not	defined, definition 0 is bound to the specified
     lighting resource.

     The eight light sources, named LIGHT0 through LIGHT7, are enabled when
     bound to a	light source definition	other than 0.  Light source positions
     are transformed by	the current ModelView matrix when the source is	bound.
     The object-coordinate position of the light source	is maintained in the
     definition	so that	subsequent bindings are	transformed from it, rather
     than from the previously transformed position.  A light source definition
     cannot be bound to	more than one lighting resource	in a single window.

     The default lighting model	uses only a single material, namely the
     material definition that is bound to MATERIAL.  Likewise, when a lighting
     model with	TWOSIDE	specified is bound, MATERIAL is	used for both front
     and back facing polygons if BACKMATERIAL is bound to material definition
     0.	 However, if a material	definition other than 0	is bound to
     BACKMATERIAL, two-sided lighting uses MATERIAL for	frontfacing polygons
     and BACKMATERIAL for backfacing polygons.	In all cases points, lines,
     and characters are	lighted	using MATERIAL.

     Lighting models use only material and light properties that are
     appropriate to them.  Other properties, such as color map mode properties
     while the current framebuffer is in RGB mode, are ignored.

SEE ALSO    [Toc]    [Back]

     lmcolor, lmdef, mmode, n, nmode

NOTES    [Toc]    [Back]

     Lighting requires that the	matrix mode be multi-matrix.  It does not
     operate correctly while mmode is MSINGLE.

     Indigo ELAN, XS, XS-24 and	XZ family requires a gconfig call before
     lmbind is called, this is especially true to render in RGBmode.  IRIS-4D
     G,	GT, and	GTX models, and	the Personal Iris, do not support two-sided
     lighting, and therefore do	not support light resource BACKMATERIAL.

     It	is a common error to bind a light source when an inappropriate
     ModelView matrix is on the	stack.	Be careful!


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