Modulef
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7.2 Position and clipping

```
      SUBROUTINE POSIT(XIN, YIN, XOUT, YOUT, I)
      REAL XIN, YIN, XOUT, YOUT
      INTEGER I
```
This subroutine converts the object's coordinates into centimeters on the screen, or the inverse.

On entry: XIN, YIN
On exit: XOUT, YOUT

If I=0: XIN, YIN point in the user space
XOUT, YOUT homologue in centimeters

If I=1: XIN, YIN in centimeters
XOUT, YOUT homologue in the user space

If I=2: XOUT, YOUT current point in the user space.

The subroutines which follow are used to define a point and line positions in relation to the mask defined for the object:

```
      SUBROUTINE QFEN(RECTI, F, RECT)
      REAL RECTI(4), RECT(4), F(4)
```
calculates the largest rectangle homologous to RECTI in F.

Input:

RECTI: initial rectangle (only the dx and dy are important) and
F: rectangle in which it is contained.

Output: RECT: rectangle homologous to RECTI contained in F.
```
      SUBROUTINE QMSQ(MASQUI, F, MASQUE)
      REAL MASQUI(4), MASQUE(4), F(4)
```
calculates a non-deforming mask to view MASQUI in window F.

Input:

MASQUI: initial mask and
F: window in which we want to view.

Output: MASQUE: non-deforming mask for the window.
```
      SUBROUTINE  SCSPT2(P, MASQ, FREJET)
      REAL MASQ(4)
      REAL P(4)
      LOGICAL FREJET
```
MASQ is a rectangular mask defined by:

MASQ(1) = XMIN
MASQ(2) = XMAX
MASQ(3) = YMIN
MASQ(4) = XMAX
P(1:2) are the coordinates of a point in the 2D space
P(3) = 0.
P(4) = 1.

On exit we have:

FREJET =.TRUE. : P is not inside the rectangle defined by MASQ.
FREJET =.FALSE. : P is inside the rectangle defined by MASQ.
```
     SUBROUTINE SCSPT3(P, MASQ, FREJET)
     REAL P(4), MASQ(6) 
     LOGICAL FREJET
```
MASQ is a parallelopipedic mask defined by:

MASQ(1) = XMIN
MASQ(2) = XMAX
MASQ(3) = YMIN
MASQ(4) = XMAX
MASQ(5) = ZMIN
MASQ(6) = ZMAX
P(1:3) are the point coordinates in the 3D space.
P(4) = 1.

On exit we have:

FREJET =.TRUE. P is not inside the parallolepiped by MASQ.
FREJET =.FALSE. P is inside the parallelopiped defined by MASQ.
```
     SUBROUTINE SCSO2D(P1, P2, MASQ, FREJET, FCLIP2)
     REAL P1(4), P2(4), MASQ(4) 
     LOGICAL FREJET, FCLIP2
```
MASQ is a rectangular mask defined by:

MASQU(1) = XMIN
MASQU(2) = XMAX
MASQU(3) = YMIN
MASQU(4) = XMAX
P1(1:3), P2(1:3) define a segment
P1(4) = 1.
P2(4) = 1.

On exit we have:

P1 and P2: The extremities of the part of the segment which falls inside the rectangle defined by MASQ.
FREJET =.TRUE. if no point of the segment falls inside the rectangle;
FALSE. if not.
FCLIP2 =.TRUE. if point P2 is falls outside the rectangle;
FALSE. if not.
```
     SUBROUTINE SCSO3D(P1, P2, MASQ, FCLIPZ, FREJET, FCLIP2)
     REAL P1(4), P2(4), MASQ(4) 
     LOGICAL FREJET, FCLIP2, FCLIPZ
```
MASQ is a parallelopipedic mask defined by:

MASQU(1) = XMIN
MASQU(2) = XMAX
MASQU(3) = YMIN
MASQU(4) = XMAX

Depending on the case under consideration:
MASQU(5) = ZMIN
MASQU(6) = ZMAX
P1(1:3), P2(1:3) define a segment
P1(4) = 1.
P2(4) = 1.

This subroutine performs a pyramidal splitting of segment P1 P2.
Let us assume that we return to the normal case where the observer is positioned at the origin and looks in the negative Z direction (see the description of subroutine NRMLST).
The vision pyramid is limited by planes X-Z=0, X+Z=0, Y+Z=0, Y-Z=0., where:
P1 and P2 contains the extremities of the part of the segment inside the cone.
FCLIPZ =.TRUE. : the cone is, in addition, limited by the planes:
Z = MASQ(5)
Z = MASQ(6)
FREJET =.TRUE. if no point in the segment falls inside the cone
FALSE. if not

FCLIP2 =.TRUE. if point P2 is outside the cone
FALSE. if not
```
     SUBROUTINE SCSC3D(P1, P2, MASQ, FREJET, FCLIP2)
     REAL P1(4), P2(4), MASQ(4) 
     LOGICAL FREJET, FCLIP2
```
performs a split of segment P1 P2 by a rectangular parallelopiped. MASQ is a parallelopipedic mask defined by:

MASQU(1) = XMIN
MASQU(2) = XMAX
MASQU(3) = YMIN
MASQU(4) = XMAX

Depending on the case under consideration:
MASQU(5) = ZMIN
MASQU(6) = ZMAX
P1(1:3), P2(1:3) define a segment
P1(4) = 1.
P2(4) = 1.

On return we have:

P1 and P2: the extremities of the part of the segment which falls inside the parallelopiped.
FREJET =.TRUE. if no point of the segment falls inside the parallelopiped;
FALSE. if not.
FCLIP2 =.TRUE. if point P2 is outside the parallelopiped.
FALSE. if not.
```
      LOGICAL  FUNCTION  APPART(A, B, X, Y, DX, DY)
      REAL A, B, X, Y, DX, DY
```
Does the point A, B fall inside the rectangle X, Y, DX, DY? If yes APPART becomes .TRUE.
```
      LOGICAL FUNCTION TSTRJT(I)
```
returns the value of FREJET after calling LIN2TO or LIN3TO.
.TRUE. if the line is rejected completely. I is a fictitious argument.
```
      LOGICAL FUNCTION TSTRJX(I)
```
checks if the text is rejected or not .
.TRUE. if totally rejected or rejection of the 2 extremity. I is a fictitious argument.
```
      SUBROUTINE SHUNT2(LOGIC)
      LOGICAL LOGIC
```
If LOGIC=.TRUE., the generation of the graphics code for 2D images is not executed (LIN2TO, MOV2TO,... ,2D library,...).
Subroutine ACTIO2 is executed instead:
```
      SUBROUTINE ACTIO2(X1, Y1, X2, Y2) 
      REAL X1, X2, Y1, Y2
```
This is a user subroutine . The coordinates (X1, Y1) and (X2, Y2) are in centimeters. It retrieves what was plotted without SHUNT2.
```
      SUBROUTINE SHUNT3(LOGIC)
      LOGICAL LOGIC
```
If LOGIC=.TRUE. the generation of the graphics code for 3D images is not executed (LIN3TO, MOV3TO,..., 3D library,...)
Subroutine ACTIO3 is executed instead:
```
      SUBROUTINE ACTIO3(X1, Y1, Z1, X2, Y2, Z2)
      REAL X1, Y1, Z1, X2, Y2, Z2
```
This subroutine is written by the user . The coordinates (X1, Y1, Z1) and (X2, Y2, Z2) are in centimeters. It retrieves what was plotted without SHUNT3.

Next: 7.3 Particular displays Up: 7 Internal programs Prev: 7.1 Interrogation subroutines Contents