Sketchy physics replay - Mac

[mptak]

I'm trying to take advantage of one of the great assets of the mac version of sketch up and sketchy physics, the transparent background. Any suggestion on how to capture frames in sketchy physics so that the background is transparent. For now I am just exporting an image per frame so that I can control the resolution and frame size but I would guess there is a better way and a better tinkerer out there who can tell me. This code was nicked from Mr. K and works to interpolate camera positions between scenes while saving an image every frame. Put the code in the on tick box of any sketchy physics solid.

if frame==0
  @transition_time=100
  @pages=Sketchup.active_model.pages
  @cam=Sketchup.active_model.active_view.camera
  @view=Sketchup.active_model.active_view
  @page_num=@pages.count-1
  @cur_page=0
  @next_page=1
end

if frame>0
  per=frame%@transition_time
  if per==0
    @cur_page+=1
    @next_page+=1
    @cur_page=0 if(@cur_page>@page_num)
    @next_page=0 if(@next_page>@page_num)
  end
  per=per.to_f/@transition_time
  page_cam1=@pages[@cur_page].camera
  page_cam2=@pages[@next_page].camera
  fov,eye,target,up=interpolate_camera(page_cam1,page_cam2,per)
  @cam.fov=fov
  @cam.set(eye,target,up)
  @newview=@view.refresh
  framet=frame.to_s
  while framet.length< 4
    framet="0"+framet
  end
  @name="/Users/markptak/Desktop/tempimage/write_image."+framet+".png"
  keys={
      ;filename => @name,
      ;width => 1924,
      ;height => 1080,
      ;antialias => false,
      ;compression => 0.9,
      ;transparent => true
      }
  @newview.write_image keys
end

if frame==0
 def interpolate_camera(cam1,cam2,per2)
   per1=1-per2
   fov1=cam1.fov
   fov2=cam2.fov
   fov=fov1*per1+fov2*per2
   eye=[]
   eye1=cam1.eye.to_a
   eye2=cam2.eye.to_a
   (0..2).each{|index| eye[index]=eye1[index]*per1+eye2[index]*per2}
   tar=[]
   tar1=cam1.target.to_a
   tar2=cam2.target.to_a
   (0..2).each{|index| tar[index]=tar1[index]*per1+tar2[index]*per2}
   up=[]
   up1=cam1.up.to_a
   up2=cam2.up.to_a
   (0..2).each{|index| up[index]=up1[index]*per1+up2[index]*per2}
   return fov,eye,tar,up
  end
end