The reject loop single point clipping code is very similar to the analogous code in the accept loop. It calls
the same clipping subroutines in lines 520-617. Then the point that was just calculated is transformed,
scaled and translated and stored in the output list (lines 305-321). Finally, the new point (which was ac-
cepted) is transformed, scaled and translated (lines 327-345). Control is transferred to the accept loop.
REJECT LOOP DOUBLE POINT CLIPPING CODE
Lines 359-492 are a direct implementation of a clipping algorithm using endpoint coordinates given in {1}.
The clipping method using determinants is not powerful enough to handle the cases where the line is re-
jected but not trivially rejected. Thus, the line parameters t1 and t2 are calculated explicitly. The t1 param-
eter is calculated based on the coordinates of the old point and the t2 parameter is calculated based on
the current point.
These parameters are calculated by a set of double point clipping subroutines in lines 631-853. These sub-
routines are called based on the coordinates in lines 359-395.
The line is checked for rejection which occurs when t1 > t2. If the line is not rejected, the plane intersections
are interpolated based on t1 and t2 (lines 409-431). Then the two new points are transformed, scaled and
translated in lines 437-478. Control is then transferred to the reject loop.
If the line is rejected, control is transferred to the reject loop after some housekeeping is performed.
TERMINATION CODE
Lines 499-509 swallow the line delimiter code (-1.0) if it is the last coordinate in the display list. Then it adds
the end of display list code (-2.0) to the display list and exits.
REFERENCE
{1} William M. Newman and Robert F. Sproull, Principles of Interactive
Computer Graphics, (New York: McGraw-Hill, 1979).
;
; WIRE-FRAME RENDITION OF A THREE DIMENSIONAL POLYLINE
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;
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;---------------------------------------------------------
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;
;
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; Transform to clip space
B-88
ON THE MOTOROLA DSP96002
Version 1.00
18-Nov-88
First point
DSP96002 USER'S MANUAL
MOTOROLA