   spotlight cutoff problem
  hi everyone.i''m working with a spotlight and i have it positioned at (0, 0, 0), with a direction of (1, 0, 1)  (i assume that would be pointed diagonally in the direction of (1, 0, 1)? )my question is, when i specify a spot cut off, any cut off value i put in at or under 90.0 shows no light whatsoever. but at 90.1 or above, i get lighting on my objects.does anyone have an explanation for this? thanks! 
  According to The Redbook, the GL_SPOT_CUTOFF parametter is 180 by default. and is restricted to the range 0-90 unless it is 180 or another special value. So that means if you specify over 90 it will not accept it there for it stays 180. You might be aiming it wrong or something.   "I seek knowledge and to help those who also seek it" ;  let me just get this straight though.the GL_POSITION specifies the point in space where the light actually is, right?and the GL_SPOT_DIRECTION specifies the point the spot light is aiming at? is this correct?because even if my object lies at the origin (0,0,0), and i position my light at (0,1,0), and have it point at (0,0,0), only spot cutoffs greater than 90 work. anything equal to or less than 90 yield no light.p.s. does the spot direction need a w coordinate, or am i safe inputting just 3 coordinates (x,y,z)? ;quote:Original post by deryk  let me just get this straight though.the GL_POSITION specifies the point in space where the light actually is, right?Yes.quote:Original post by deryk  and the GL_SPOT_DIRECTION specifies the point the spot light is aiming at? is this correct?It is the direction of the light, not a point it is looking at. if you say {0,0,-1} it points forward into the screen no matter what the position.quote:Original post by deryk  because even if my object lies at the origin (0,0,0), and i position my light at (0,1,0), and have it point at (0,0,0), only spot cutoffs greater than 90 work. anything equal to or less than 90 yield no light.As I said eailer, Any value over 90 will result in no change, so it is not a spotlight,so, it is an omni light. maybe I didn''t state it clearly enought.quote:Original post by deryk  p.s. does the spot direction need a w coordinate, or am i safe inputting just 3 coordinates (x,y,z)?   No there is no w coord, just x,y,z "I seek knowledge and to help those who also seek it" 