globes

GLOBES

The multiple camera views used to capture the environment are controlled by a "globe" script. It expects the following symbols, which we will go into more detail:

• plates (array of [forward, up, fov] objects)
• globe_plate (optional function (x,y,z) -> plate index)

Coordinate System:

     +Y = up
        ^
        |
        |
        |    / +Z = forward
        |   /
        |  /
        | /
        0------------------> +X = right

NOTE: Plate coordinates are relative to the camera's frame. They are NOT absolute coordinates.

Defining Plates

plates is an array, with each element containing a single camera's forward vector, up vector, and fov. Together, the plates should form a complete globe around the player. For example, this is from cube.lua:

plates = {
   -- forward     up           fov
   { { 0, 0, 1 }, { 0, 1, 0 }, 90 }, -- front
   { { 1, 0, 0 }, { 0, 1, 0 }, 90 }, -- right
   { { -1, 0, 0 }, { 0, 1, 0 }, 90 }, -- left
   { { 0, 0, -1 }, { 0, 1, 0 }, 90 }, -- back
   { { 0, 1, 0 }, { 0, 0, -1 }, 90 }, -- top
   { { 0, -1, 0 }, { 0, 0, 1 }, 90 } -- bottom
}

It creates the following plates:

          ---------
          |       |
          | TOP   |
          |       |
          ---------
--------- --------- --------- ---------
|       | |       | |       | |       |
| LEFT  | | FRONT | | RIGHT | | BACK  |
|       | |       | |       | |       |
--------- --------- --------- ---------
       ^  ---------
       |  |       |
      90º |BOTTOM |
       |  |       |
       v  ---------
          <--90º-->

Resolving Plates

In order to resolve a given direction vector to a color, we must figure out which plate plate that color will come from. The default behavior is to just choose the plate whose center has the smallest angular distance from the vector. You can optionally define a globe_plate function to add your own behavior.

globe_plate takes a vector, and returns a plate index. For example, fast.lua uses two plates pointed in the same direction (with 90º and 160º). The following function resolves all vectors inside the 90x90º window to the 90º plate, and everything outside of it is resolved to the 160º plate:

small = 0
big = 1
big_fov = 160

plates = {
{ {0,0,1}, {0,1,0}, 90 },
{ {0,0,1}, {0,1,0}, big_fov}
}

function globe_plate(x,y,z)
   if z <= 0 then
      return nil
   end

   local dist = 0.5 / tan(big_fov*pi/180/2)
   local size = 2*dist*tan(pi/4)

   local u = x/z*dist
   local v = y/z*dist

   local plate
   if abs(u) < size/2 and abs(v) < size/2 then
      return small
   else
      return big
   end
end

Usage

To use a globe in-game, enter the command:

f_globe <name>

Debugging

To see each of the current globe's plates on screen in a table, you can use the debug lens:

f_lens debug

Available globes

• cube: front-facing cube
• cube_edge: edge-facing cube
• cube_corner: corner-facing cube
• trism: a triangular prism with 5 views
• tetra: a tetrahedron with 4 views
• fast: 2 overlaid views in the same direction (90 and 160 degrees)