it's called texturefilter. Example code from the IDE:
Open in online IDE; ClearTextureFilters and TextureFilter Example. ; ---------------------------------------------- Const tex_color = 1 ; Color texture Const tex_alpha = 2 ; Alpha texture (Include alpha channel data) Const tex_mask = 4 ; Masked texture (black is transparent) Const tex_mipmap = 8 ; Create texture mipmaps Const tex_clampu = 16 ; Restrict U texture coords from "bleeding over" Const tex_clampv = 32 ; Restrict V texture coords from "bleeding over" Const tex_envshpere = 64 ; Load texture as a spherical environment map Const tex_vram = 256 ; Force texture graphics to vram Const tex_highcolor = 512 ; Forces texture graphics to be 32-bits per pixel Graphics3D 640,480 ; Removes any texture filters that might apply. ClearTextureFilters ; Add an alpha texture to the list of ; texture filters to apply to files ; that have "_alpha" in their filenames. TextureFilter "_alpha",tex_color + tex_alpha + tex_mipmap ; Set appropriate texture flags for loading ; suitable skybox textures from files named ; something with "_skybox". TextureFilter "_skybox", tex_color + tex_mipmap + tex_clampu + tex_clampv ; Set the flags for loading a spherical refletction ; map to apply to all "_refmap" files. TextureFilter "_refmap", tex_color + tex_mipmap + tex_envshpere ; Setup a texture filter to allow faster ; (and easier) pixel manipulation on all ; loaded "_fastblit" files. TextureFilter "_fastblit", tex_color + tex_vram + tex_highcolor ; This is where you would normally load your special ; textures. ; The next bit resets the texture filters to their ; standard settings. ClearTextureFilters TextureFilter "", tex_color + tex_mipmap End