raycast: add slow basic version

graphics/gr/raycast/ray.bas

@@ -0,0 +1,13 @@
+10 GR
+20 FOR Y=0 TO 39:Z=Y*0.04
+30 A=Z+H:XX=SIN(A)/2:YY=COS(A)/2:D=0:RX=PX:RY=PY
+40 D=D+1:IF D>40 THEN 60
+50 RX=RX+XX:RY=RY+YY
+55 C=0:IF ABS(RX)>16 OR ABS(RY)>16 THEN C=5
+56 IF RX>4 AND RX<6 AND RY>4 AND RY<6 THEN C=1
+57 IF C=0 THEN 40
+60 U=40/D:IF U>19 THEN U=19
+70 V=19-U:COLOR=7:VLIN0,V AT Y
+75 COLOR=C:VLINV,V+U+U AT Y
+80 COLOR=8:VLIN V+U+U,39 AT Y
+100 NEXT Y:H=H+0.2:GOTO 20