NormedTriangleMeshFormats.hs

{-# LANGUAGE OverloadedStrings #-}

-- Implicit CAD. Copyright (C) 2011, Christopher Olah (chris@colah.ca)
-- Released under the GNU GPL, see LICENSE

module Graphics.Implicit.Export.NormedTriangleMeshFormats where

import Graphics.Implicit.Definitions
import Graphics.Implicit.Export.TextBuilderUtils


obj normedtriangles = toLazyText $ vertcode <> normcode <> trianglecode
	where
		-- A vertex line; v (0.0, 0.0, 1.0) = "v 0.0 0.0 1.0\n"
		v :: ℝ3 -> Builder
		v (x,y,z) = "v "  <> bf x <> " " <> bf y <> " " <> bf z <> "\n"
		-- A normal line; n (0.0, 0.0, 1.0) = "vn 0.0 0.0 1.0\n"
		n :: ℝ3 -> Builder
		n (x,y,z) = "vn " <> bf x <> " " <> bf y <> " " <> bf z <> "\n"
		verts = do
			-- extract the vertices for each triangle
			-- recall that a normed triangle is of the form ((vert, norm), ...)
			((a,_),(b,_),(c,_)) <- normedtriangles
			-- The vertices from each triangle take up 3 position in the resulting list
			[a,b,c]
		norms = do
			-- extract the normals for each triangle
			((_,a),(_,b),(_,c)) <- normedtriangles
			-- The normals from each triangle take up 3 position in the resulting list
			[a,b,c]
		vertcode = mconcat $ map v verts
		normcode = mconcat $ map n norms
		trianglecode = mconcat $ do
			n <- map ((+1).(*3)) [0,1 .. length normedtriangles -1]
			let
				vta = buildInt  n
				vtb = buildInt (n+1)
				vtc = buildInt (n+2)
			return $ "f " <> vta <> " " <> vtb <> " " <> vtc <> " " <> "\n"