Motorola DSP96002 - Manual (Page 601)

B-82 DSP96002 USER’S MANUAL MOTOROLA
lsr d0 d0.l,d2.l
dec d2 d2.l,d4.l
neg d1 d0.l,r0
move d2.l,m0
move d1.l,n0
move d1.l,d5.l
; Draw first point
jsr _draw_point
; Draw additional points
do d4.l,_line_x_yn
inc d6 r0,d2.l
add d5,d2 (r0)+n0
cmp d4,d2
dec d7 ifge
_draw1
jsr _draw_point
_line_x_yn
rts
; Draw a single point
_draw_point
move d6.l,x:(r1)+ d7.l,y:
rts
B.1.44 Wire-Frame Graphics Rendering
WIRE-FRAME RENDITION OF A THREE DIMENSIONAL POLYLINE
ON THE MOTOROLA DSP96002
Version 1.00
OVERVIEW
This program displays a three dimensional polyline in two dimensions. The points of the polyline, as defined
in the input list, are projected into two dimensions using the perspective transformation. The projected
points are output to a display list that can be drawn by a graphics engine or a fast drawing program.
In order to maximize speed, two loops perform the graphics transformations: the trivial accept loop and the
trivial reject loop.
The trivial accept loop assumes that the last displayed point was inside the viewing pyramid and thus not
clipped. It pulls a new point from the input list, converts it to clipping space and checks if it is inside the
viewing pyramid. If so, the routine performs the perspective transformation, scales and translates the point
so it lies within the viewing window, and finally adds it to the display list.