Grass demo

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Moraldi

Looking the AGore's GrassDemo.bb located in the samples directory of Blitz3D I didn't understand anything about the following piece of code:

CameraProject(camera,EntityX(flare,1),EntityY(flare,1),EntityZ(flare,1))
	
vx# = ProjectedX() - (gwidth/2)
vy# = ProjectedY() - (gheight/2)
sx = vx + (gwidth/2) : sy = vy + (gheight/2)
PositionEntity s1,SpriteX(sx,sy,128),SpriteY(sx,sy,128),SpriteZ(sx,sy,128)
	sx = -vx/2 + (gwidth/2) : sy = -vy/2 + (gheight/2)
	PositionEntity s2,SpriteX(sx,sy,128),SpriteY(sx,sy,128),SpriteZ(sx,sy,128)
	sx = -vx/5 + (gwidth/2) : sy = -vy/5 + (gheight/2)
	PositionEntity s3,SpriteX(sx,sy,128),SpriteY(sx,sy,128),SpriteZ(sx,sy,128)
	sx = -vx/1.2 + (gwidth/2) : sy = -vy/1.2 + (gheight/2)
	PositionEntity s4,SpriteX(sx,sy,128),SpriteY(sx,sy,128),SpriteZ(sx,sy,128)
	
	RotateSprite s1,-EntityYaw(camera)
EntityAlpha s1,ProjectedZ()
EntityAlpha s2,1-(Abs(vx)/(gwidth/2))
EntityAlpha s3,1-(Abs(vx)/(gwidth/2))
EntityAlpha s4,1-(Abs(vx)/(gwidth/2))

I removed the lines above but I didn't notice a difference.
Does anyone knows what they do?

Thanks