Since we need frame sync between cards on a dual head card, where each output ist buffered once we need 4 renderbuffer on one card. Since big screens cab ve made with many projectors, or we need strange formats like 8:3 (with 2 DVDs? 16:3), we have to split the output.

• dual head cards with rendering power on both heads
• synchronisable video cards playing paralell
• maybe sharing renderpower on more cards (SLI)
• High Video Signal Quality over long distance cables.
• softedgeblending (see discussion below)

hints:

• GPL System for large screens

Discussion:

On 2. 03 2005 12:27 wolfgang schwarzenbrunner writes (pdlist excerp):

  [...]
  > >a) Quadro vs. geforce:  If I want display on multiple large screens, (is
  > >there) what is the benefits of NVIDIA quadro cards to geforce (eg. 6800
  > > SLI) on signal quality rendering benefits. ?
  >
  > well the quadro cards have one really nice feature. they have hardware soft
  > edge blending which is quiet essential when using multiple projectors on
  > one screen. soft edge blending means that they let you overlap two (or
  > more) projector and modify contrast, color and so on for the overlapping
  > area so you can kind of balance the color and contrast differences between
  > the two projectors (even if you have exactly the same type of projectors
  > differences will occur). well the quadrofx 4000 is very expensive but this
  > feature really pays (if you are looking for quality). other standalone
  > hardware doing only soft edge blending is nearly unaffordable. realizing
  > hard edge blending (no overlapping) is only possible with nearly
  > unaffordable projectors like pacos. the quadro cards can also be upgraded
  > for genlocking (which might be usefull when working with two ore more
  > computers -- well i don`t know if genlocking is really needed when working
  > with gem). i also don`t know if its possible to use the built in softedge
  > blending with four projectors.
  >
  > when it comes to signal quality i am shure that matrox card are best. there
  > are some new ones doing four outputs with full openGl power.
  > http://www.matrox.com/mga/products/qid_pro/home.cfm. well its mostly used
  > for millitary -- so i don`t know about your moralistic concerns :). and
  > does not do softedge blending.
  >
  [...]
  > >b) If I do 4 projections on a big screen so they are merged to one
  > > picture, must the video be displayed in frame sync (maybe using more than
  > > one computer) from the beamer/videocard view (not the video frames as
  > > content).  ?
  >
  > well -- genlocking issue. as said -- don`t know if its needed with gem (as
  > you trigger each frame anyway)???? never tried.
  >