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.\" 1. Substitute PHIGS Extension function name (in CAPS) for "PNAME" in line be.\"low:
.ds pN SET BACK INTERIOR SHADING METHOD
.TH "\*(pN" 3P+ "29 February 1991"
.SH NAME
\*(pN \-
create a structure element to set the back interior shading method
.IX "PHIGS Extension Functions" "\*(pN"
.IX "Filled Area Interior Attributes" "SET BACK INTERIOR SHADING METHOD"
.IX "Aspect Source Flags" "SET BACK INTERIOR SHADING METHOD"
.IX "Attributes, Filled Area Interior Attributes" "SET BACK INTERIOR SHADING METHOD"
.SH SYNOPSIS
.SS C Syntax
.ft B
.ta 1.25i 3i
.nf
.\" 6. Insert C syntax below
.nf
void
pset_back_int_shade_meth ( method )
Pint	method;	\fIback shading method\fP
.fi
.ft R
.SS Required PHIGS Operating States
(PHOP, *, STOP, *)
.SH DESCRIPTION
.SS Purpose
\s-2SET BACK INTERIOR SHADING METHOD\s+2 creates a structure 
element to set the back interior shading method.
.LP
When the current back interior shading method
\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 "NON-UNIFORM B-SPLINE SURFACE"
.LP
\(bu
.SM "SET OF FILL AREA SET 3 WITH DATA"
.LP
\(bu
.SM "QUADRILATERAL MESH 3 WITH DATA"
.LP
\(bu
.SM "TRIANGLE STRIP 3 WITH DATA"
.RE
.SS C Input Parameters
.IP \fImethod\fP
The back interior shading method.  The predefined values
are:
.sp
.nf
.ta .5i +\w'0     'u +\w'PSD_DOT_PRODUCT     'u
1	PSD_NONE	\fINo Shading\fP
2	PSD_COLOUR	\fIColour Interpolation Shading\fP
3	PSD_DOT_PRODUCT	\fIDot Product Interpolation Shading\fP
4	PSD_NORMAL	\fINormal Interpolation Shading\fP
.sp .2
.fi
.SS Execution
Depending on the edit mode, a \s-2SET BACK INTERIOR SHADING METHOD\s+2
element with the value shading method 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 SHADING METHOD\s+2
element.
.LP
When the structure is traversed, the current interior
shading method entry in the traversal state list is set to the
specified value. This value is used with subsequent
\s-2PHIGS\s0 Extension output primitives
when the current interior shading method \s-2ASF\s+2 entry
in the traversal state list is \s-2INDIVIDUAL\s+2.
During traversal, if the specified shading method is not available
on a workstation, method one (\fINone\fP) will be used on that workstation.
.LP 
The interior shading method supported by a workstation type can be determined 
with the function \s-2INQUIRE INTERIOR FACILITIES PLUS\s+2.
.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 
only to 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 shading method \s-2ASF\s+2 is set to
\s-2INDIVIDUAL\s+2, area-defining output primitives, which follow in
the structure network and are subject to back face attributes, are filled
using the current back interior shading method.
.LP
When the current back interior shading method \s-2ASF\s+2
is set to \s-2BUNDLED\s+2,
the back interior shading method is taken from the
workstation extended representation indicated by the current interior index.
In this case, the back interior shading meth
set with \s-2SET BACK INTERIOR SHADING METHOD\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 INTERIOR SHADING METHOD (3P+)"
.fi