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*The graPHIGS Programming Interface : Subroutine Reference*

## GPCVMT - Compute View Matrix

**Purpose**

Use
**GPCVMT** to calculate a
view matrix
based upon
the values present in the Utility State List (USL)
This view matrix is used as the view matrix parameter on
the Set Extended View Representation
(**GPXVR**)
subroutine.

The matrix returned will perform a change of coordinate
system from the World Coordinate (WC)
system to a Viewing Coordinate (VC) system
in which the origin is the view reference point,
the n-axis is the view plane normal,
and the v-axis lies in
the half plane designated by the View Up vector.
This matrix represents the change of coordinate systems by
a translation operation followed by a rotation operation.

If the matrix cannot be calculated,
the graPHIGS API issues an error.

**Parameters**

*matrix* -- returned by the graPHIGS API,
16 short floating-point numbers
Transformation matrix.
The elements are returned in the following
order for the transformation
matrix:

|m11 m12 m13 m14|
|m21 m22 m23 m24| ---> (m11,m12,m13,m14,m21,...m44)
|m31 m32 m33 m34|
|m41 m42 m43 m44|

**Error Codes**

**58**
- UP AND PLANE NORMAL VECTORS ARE PARALLEL

**Related Subroutines**

None

**RCP code**

201331204
(X'0C001204')

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