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.ds f \s-2SET BACK INTERIOR REFLECTANCE EQUATION\s+2
.TH "SET BACK INTERIOR REFLECTANCE EQUATION" 3P+ "29 February 1991"
.SH NAME
SET BACK INTERIOR REFLECTANCE EQUATION \-  create a structure element to set
the current back interior reflectance equation   
.IX "PHIGS Extension Functions" "SET REFLECTANCE EQUATION"
.IX "Filled Area Interior Attributes" "SET BACK INTERIOR REFLECTANCE EQUATION"
.IX "Aspect Source Flags" "SET BACK INTERIOR REFLECTANCE EQUATION"
.IX "Attributes, Filled Area Interior Attributes" "SET BACK INTERIOR REFLECTANCE EQUATION"
.SH SYNOPSIS
.SS C Syntax
.ft B
.ta 1.25i 3i
.nf
void
pset_back_refl_eqn ( equation )
Pint	equation;	\fIback reflectance equation\fP
.fi
.ft R
.SS Required PHIGS Operating States
(PHOP, *, STOP, *)
.SH DESCRIPTION
.SS Purpose
\s-2SET BACK INTERIOR REFLECTANCE EQUATION\s+2 creates a structure
element to set
the current back interior reflectance equation.
.LP
When the current back interior reflectance equation
\s-2ASF\s+2 is set to \s-2INDIVIDUAL\s+2, the current value of
this attribute applies to the following output primitives:
.RS
.LP
\(bu
.SM "FILL AREA"
.LP
\(bu
.SM "FILL AREA 3"
.LP
\(bu
.SM "FILL AREA SET"
.LP
\(bu
.SM "FILL AREA SET 3"
.LP
\(bu
.SM "FILL AREA SET 3 WITH DATA"
.LP
\(bu
.SM "SET OF FILL AREA SET 3 WITH DATA"
.LP
\(bu
.SM "NON-UNIFORM B-SPLINE SURFACE"
.LP
\(bu
.SM "QUADRILATERAL MESH 3 WITH DATA"
.LP
\(bu
.SM "TRIANGLE STRIP 3 WITH DATA"
.RE
.SS C Input Parameters
.IP \fIequation\fR
The reflectance equation.  The possible values defined in phigs.h are:
.sp
.nf
.ta .5i +\w'0     'u +\w'PREFL_AMB_DIFF_SPEC     'u
1	PREFL_NONE	\fINo Reflectance Calculation Performed\fP
2	PREFL_AMBIENT	\fIUse Ambient Term\fP
3	PREFL_AMB_DIFF	\fIUse Ambient and Diffuse Terms\fP
4	PREFL_AMB_DIFF_SPEC	\fIUse Ambient, Diffuse, and Specular Terms\fP
.sp
.fi
.SS Execution
Depending on the edit mode, a \s-2SET BACK INTERIOR REFLECTANCE EQUATION\s+2
element with the value reflectance equation is inserted into the open
structure after the element pointer or replaces the element pointed
at by the element pointer. The element pointer is then updated to 
point to this \s-2SET BACK INTERIOR REFLECTANCE EQUATION\s+2
element.
.LP
At traversal time, if the specified reflectance equation is not defined,
then the default is used.
.LP
Back face attributes (such as back area properties, 
back interior colour, back interior reflectance equation, 
back interior shading method, back interior style, and
back interior style index) are used only when the
face distinguishing mode has the value \fIYes\fP and are applied to
only the back facing portion of area defining primitives. See 
\s-2SET FACE DISTINGUISHING MODE (3P+)\s+2 for details on front and back face 
determination.
.LP
When the current back interior reflectance equation \s-2ASF\s+2 is set to
\s-2INDIVIDUAL\s+2, area-defining output primitives which follow in
the structure network are filled using the current
back interior reflectance equation.
.LP
When the current back interior reflectance equation
\s-2ASF\s+2 is set to \s-2BUNDLED\s+2,
the back interior reflectance equation is taken from the
workstation extended representation indicated by the current interior index.
In this case, the back interior reflectance equation
set with \s-2SET BACK INTERIOR REFLECTANCE EQUATION\s+2 has no effect.
.SH ERRORS
.IP 005
Ignoring function, function requires state 
(\s-2PHOP\s+2, \s-2*\s+2, \s-2STOP\s+2, \s-2*\s+2)
.SH SEE ALSO
.nf
.IP
.ta 0.5i
.SM "SET FACE DISTINGUISHING MODE (3P+)"
.SM "SET INDIVIDUAL ASF (3P)"
.SM "SET INTERIOR REPRESENTATION PLUS (3P+)"
.SM "SET REFLECTANCE EQUATION (3P+)"
.SM "FILL AREA (3P)"
.SM "FILL AREA 3 (3P)"
.SM "FILL AREA SET (3P)"
.SM "FILL AREA SET 3 (3P)"
.SM "FILL AREA SET 3 WITH DATA (3P+)"
.SM "SET OF FILL AREA SET 3 WITH DATA (3P+)"
.SM "NON-UNIFORM B-SPLINE SURFACE (3P+)"
.SM "QUADRILATERAL MESH 3 WITH DATA (3P+)"
.SM "TRIANGLE STRIP 3 WITH DATA (3P+)" 
.fi
