{-
Matrix Manipulation Code.
The key to doing rotations and movement in a 3D system is to use
matrix math.

Since there are going to be no translations in this engine, i'm
dumping the 4th row and col in the matrix math.

-}

module Mat3d where

import Vec3d

{-               X       Y      Z      W -}
type Matrix3 = (Float, Float, Float,
                Float, Float, Float,
		Float, Float, Float)

ident :: Matrix3
ident = (1, 0, 0,
	 0, 1, 0,
	 0, 0, 1)

vecMultMat :: Vector3 -> Matrix3 -> Vector3
vecMultMat (x, y, z) m = (x', y', z')
    where (xx,xy,xz,
	   yx,yy,yz,
	   zx,zy,zz) = m
	  x' = x*xx + y*yx + z*zx
	  y' = x*xy + y*yy + z*zy
	  z' = x*xz + y*yz + z*zz

{-
These functions are used to generate a the rotation matricies
-}
rotX :: Float -> Matrix3
rotX theta = (1, 0,   0, 
	      0, cx,  sx,
	      0, nsx, cx)
    where cx = cos theta
	  sx = sin theta
	  nsx = -sx

rotY :: Float -> Matrix3
rotY theta = (cy, 0, nsy,
	      0,  1, 0,  
	      sy, 0, cy)
    where cy = cos theta
	  sy = sin theta
	  nsy = -sy

rotZ :: Float -> Matrix3
rotZ theta = (cz,  sz, 0,
	      -sz, cz, 0,
	      0,   0,  1)
    where cz = cos theta
	  sz = sin theta
	  

{- Scaling.  Not as important -}
scale x y z = (x, 0, 0,
	       0, y, 0,
	       0, 0, z)

rotTest1 = (0,0,0) `vecMultMat` (rotY pi)
rotTest2 = (1,0,0) `vecMultMat` (rotY pi)
rotTest3 = (0,1,0) `vecMultMat` (rotY pi)
rotTest4 = (0,0,1) `vecMultMat` (rotY pi)