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*The graPHIGS Programming Interface : Subroutine Reference*

## GPEVM3 - Evaluate View Mapping Matrix 3

**GPEVM3
(***window*,
*viewpt*,
*type*,
*point*,
*dist*,
*near*,
*far*,
*errind*,
*matrix*) |

**Purpose**

Use
**GPEVM3** to create a view mapping matrix.
The matrix can be used
as input to the Set Extended View Representation
(**GPXVR**)
subroutine.

If the view mapping matrix can be computed, the error indicator
is set to zero, and the matrix is returned.
If the matrix cannot
be computed, the error indicator contains an error number
indicating the reason.
In this case, the value of the output
parameter is unpredictable.

**Parameters**

*window* -- specified by user,
4 short floating-point numbers (VC)
Window limits (Umin, Umax, Vmin, Vmax)
*viewpt* -- specified by user,
6 short floating-point numbers
(NPC)
Viewport limits (Xmin, Xmax, Ymin, Ymax, Zmin, Zmax)
*type* -- specified by user, fullword integer
Projection type
(`1=PARALLEL, 2=PERSPECTIVE`
)
*point* -- specified by user,
3 short floating point numbers (VC)
Projection reference point
(*U*,
*V*,
*N*)
*dist* -- specified by user,
short floating-point number (VC)
Distance of view plane from view reference point along n-axis.
*near* -- specified by user,
short floating-point number (VC)
Distance of near plane from view reference point along n-axis.
*far* -- specified by user,
short floating-point number (VC)
Distance of far plane from view reference point along n-axis.
*errind* -- returned by the graPHIGS API, fullword integer
If the error indicator is zero, the request has been
completed. Otherwise, one of the following errors exists:
**44**
- INVALID WINDOW DEFINITION
**55**
- PRP IS POSITIONED ON THE VIEW PLANE
**330**
- INVALID VIEWPORT
**331**
- PROJECTION TYPE IS INVALID
**336**
- FAR CLIPPING PLANE IN FRONT OF NEAR CLIPPING PLANE
**608**
- FRONT PLANE DISTANCE = BACK PLANE DISTANCE WHEN Z-EXTENT NON-ZERO
**610**
- PROJECTION REFERENCE POINT BETWEEN NEAR AND FAR PLANES

*matrix* -- returned by the graPHIGS API,
16 short floating-point numbers
View mapping matrix.
The elements are returned in the following order
for the view mapping matrix:
|m11 m12 m13 m14|
|m21 m22 m23 m24| ---> (m11,m12,m13,m14,m21,m22,...m44)
|m31 m32 m33 m34|
|m41 m42 m43 m44|

**Error Codes**

None

**Related Subroutines**

**GPXVR**
- Set Extended View Representation

**RCP code**

201331207
(X'0C001207')

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