ZXASCII
AUTO -1
PROG demos:graphics/cylinder
CHANGED FALSE
10 REM Sky Cylinder
20 radians:
	GRAPHIC NEW s LOAD "sky.png":
	PALETTE COPY s,0,256 TO 0:
	gw=GFXw s,gh=GFXh s:
	WINDOW NEW sky,0,0,gw,gh:
	WINDOW HIDE sky:
	WINDOW PUT GRAPHIC s,sky,0,0:
	WINDOW 0
30 fov=90,hw=SCRw/2,hh=SCRh/2,unit=hw/TAN(fov*.5):
	DIM ao(SCRw) BASE 0;ch(SCRw) BASE 0
40 FOR x=0 TO hw-1:
	   ao(hw+x)=ATN(x/unit),
				ao(hw-1-x)=-ao(hw+x),
				ch(hw+x)=SCRh/COS ao(hw+x),
				ch(hw-1-x)=ch(hw+x):
	NEXT x
50 va=180:
	DO:
	   va+=1:
				FOR x=0 TO SCRw-1:
				   th=ch(x),th2=th/2,u=0:
							u+=va+ao(x)*100:
							WINDOW COPY sky,((u mod 360)/360)*gw,0,1,gh TO 0,x,hh-th2,1,hh+th2:
				NEXT x:
				WAIT SCREEN:
	LOOP