bmap_to_cubemap

bmap_to_cubemap( BMAP*)

Converts a six-sided sky cube bitmap into a cubic environment map, which can be used for enviroment mapping or shader effects.

Parameters:

BMAP* - pointer to sky cube bitmap

Remarks:

The bmap must look like a sky cube (see image below): consisting of 6 adjacent square cube faces in the order south, east, north, west, down, up. Thus its width must be six times larger than its height. The faces must be tiled in a way that they can be wrapped around a cube. Each cube face must be a power of 2 in size.
Some old 3D cards (ATI) do not support cubic environment maps with cube sizes larger than 256x256.
For mipmapped environment maps, create the mipmaps before calling bmap_to_cubemap (like bmap_to_cubemap(bmap_to_mipmap(skymap)). Creating mipmaps afterwards will produce an invalid environment map.
For rendering into a face of an environment map, set the view pos_x parameter to the pixel position of the beginning of the face you want to render into. Some 3D card drivers do not support rendering into an environment map that is visible in the same view. Use the NOFLAG1 or ENABLE_TREE method to exclude the environment mapped objects from the render views.

Speed:

Slow

Edition:

C P

Example:

BMAP* bmpEnviro = "skybox+6.tga";

MATERIAL* mtlEnviro =
{
   skin2 = bmpEnviro;
   effect = "
      texture mtlSkin2;
      technique enviro
      {
         pass P0
         {
            Texture[0] = <mtlSkin2>;
            AddressU[0] = Clamp; // don't wrap around edges
            AddressV[0] = Clamp;
            ColorOp[0] = SelectArg1; // ignore the ambient light
            ColorArg1[0] = Texture;
            TexCoordIndex[0] = CameraSpaceReflectionVector;
            TextureTransformFlags[0] = Count3;
         }
      }

      technique fallback { pass p0 { } } // empty fallback causes normal rendering without effect
   ";
}

function mtlEnviro_startup()
{
   bmap_to_cubemap(mtlEnviro.skin2);
}

See also:

CUBE, view.bmap

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