spotlight introducing wierd shadow

Posts

• fluxfire181 Posts: 604Member

  May 2007 #2

  

  Did you take into account the size of the spot light as you move the light back away from the models? I know that sounds stupid. but can't rule out the simple things
• biotech171 Posts: 0Member

  May 2007 #3

  

  Try using area shadows, see if that helps.
• IRML253 Posts: 1,993Member

  May 2007 #4

  

  ok firstly biotech - he was asking "how this happened" not for an alternative shadow option, and he'd be using area shadows if he wanted to, shadow maps is for saving render time, so that's a pretty lame suggestion
  
  lancer - the reason for this is because the shadow map is just an image of the shadow, blurred and then projected onto the geometry, when you put the light close up you're getting a lot of that image projected onto the geometry, but when you move further away the geometry takes up a smaller part of that image, so the shadow you see on the model effectivly becomes a lot lower resolution than 2048, meaning you get inaccuracies like funny edges to the shadows and gaps in the shadows making it look like light comming is through, which is your problem
  
  if you've moved the light back so it illuminates more ships then the only way you can fix this is to make the resolution of the map higher, but if you think you can get away with the light where it is but only the main ship having shadows on it then you change the area that the shadow map projects on, so it'll be like it was when you had the light closer to the ship
• mattc181 Perth, AuPosts: 322Member

  May 2007 #5

  

  i.e. use area lights and don't worry about pesky shadow maps
• lancer0 Posts: 0Member

  May 2007 #6

  ah got you. so it's a shadow map thing, hmm makes sense. what if I created a spotlight per ship that lights that ship and that ship only?
  
  keeps the spot close in, gives me more complete shadow control and also what is an isn't lit. or from a pro SFX standpoint, is area lights with ray traced shadows the way to be going?
  
  btw, thinking about this whole shadow map projection thing, would that explain how I sometimes get wierd shadow movement in an animation as the generated shadow map is not moving the same as the actual ship it is being projected on to.
• Comco317 Posts: 1,281Administrator

  May 2007 #7

  

  lancer wrote: »

  btw, thinking about this whole shadow map projection thing, would that explain how I sometimes get wierd shadow movement in an animation as the generated shadow map is not moving the same as the actual ship it is being projected on to.

  
  That would stand to reason. I am not an expert on such matters but I always prefer to use Raytraced shadows for space scenes...It renders a shadow based on a true 'line of sight' solution if I understand correctly...So the results are far more consistent between frames etc. It also gives a sharper more 'realistic' looking image in most cases and also helps bring out fine modeled details in a mesh that shadow mapping simply isn't robust enough to do...Take a model with a reasonable amount of detail, render it with shadow maps then change to raytraced and you should see what I mean...
  
  Back in the old days when more than a few of us were doing this stuff with Pentium 2s and 3s, raytraced shadows meant a huge bump in rendering time. Fortunately, with CPU speeds being what they are today, that particular drawback isn't a big deal anymore...