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*GL3.2 for AIX: Graphics Library (GL) Technical Reference*

## mapw2 Subroutine

### Purpose

Computes the inverse mapping from screen coordinates to 2-D modeling coordinates.

### Libraries

Graphics Library

C (**libgl.a**)

FORTRAN (**libfgl.a**)

### C Syntax

**void mapw2**
**(Int32 ***viewobj***, **
**Screencoord** *screenx***, Screencoord** *screeny***, **
**Coord ****modelx***, Coord ****modely***)**

### FORTRAN Syntax

**SUBROUTINE MAPW2(***viewobj***, ***screenx***, ***screeny***, ***modelx***, ***modely***)**
**INTEGER*4 ***viewobj***,*** screenx***, ***screeny*
**REAL ***modelx***, ***modely*

**Note: **For FORTRAN users, this subroutine accepts long integer parameters (INTEGER*4) when invoked from a FORTRAN program, although it accepts short integers when invoked from a C program. The C and FORTRAN syntax shown here reflect this difference.

### Description

The **mapw2** subroutine maps a point on the screen into 2-D
modeling coordinates. This subroutine is the 2-D version of the **mapw** subroutine.

**Note: **This subroutine cannot be used to add to a
display list.

### Parameters

*viewobj* |
Specifies a primitive containing the viewport, projection, viewing, and modeling
transformations that define modeling space. |

*screenx* |
Specifies a point in screen coordinates. |

*screeny* |
Specifies a point in screen coordinates. |

*modelx* |
Specifies the corresponding *x* model coordinate. |

*modely* |
Specifies the corresponding *y* model coordinate. |

### Implementation Specifics

This subroutine is part of GL in the AIXwindows Environment/6000 Version 1, Release 2 with AIXwindows/3D Feature.

### Files

**/usr/include/gl/gl.h** |
Contains C language constant and variable type definitions for GL. |

**/usr/include/gl/fgl.h** |
Contains FORTRAN constant and variable type definitions for GL. |

### Related Information

Creating a new object in the display list with the **makeobj** subroutine.

Computing the inverse mapping from screen coordinates to 3-D modeling coordinates with the **mapw** subroutine.

AIX Graphics Library Overview, Picking and Selecting Overview, and Working with Coordinate Systems.

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