MiniB3D Thread 3

Alrighty then...

After banging my head against Left Handed/Right Handed Matrices for a Looong time. I've made some working additions to the TMatrix Class. Just add in these methods:

Method MultiplyVector(I:TVector var, O:TVector Var)
	Local Mt:TMatrix = New TMatrix
	Local tmp:Float[3]
	Local tmp2:Float[3]
	Local itmp3:Float
	mt.LoadIdentity
	mt.Scale(1,1,-1)
	mt.Multiply(Self)
	itmp3 = 1.0 /(I.x*mt.grid[0,3]+I.y*mt.grid[1,3]+I.z*mt.grid[2,3]+mt.grid[3,3])
	tmp[0] = itmp3*I.x
	tmp[1] = itmp3*I.y
	tmp[2] = itmp3*(I.z*-1)
	O.x=tmp[0]*(mt.grid[0,0])+(tmp[1])*(mt.grid[1,0])+tmp[2]*(mt.grid[2,0])+itmp3*(mt.grid[3,0])
	O.y=tmp[0]*(mt.grid[0,1])+(tmp[1])*(mt.grid[1,1])+tmp[2]*(mt.grid[2,1])+itmp3*(mt.grid[3,1])
	O.z=tmp[0]*(mt.grid[0,2])+(tmp[1])*(mt.grid[1,2])+tmp[2]*(mt.grid[2,2])+itmp3*(mt.grid[3,2])
End Method

Method MultiplyNormal(I:TVector var, O:TVector Var)
	Local Mt:TMatrix = New TMatrix
	mt.LoadIdentity
	mt.Scale(1,1,-1)
	mt.Multiply(Self)
	Local tmp:Float[3]
	Local itmp:Float
	tmp[0]=I.x*mt.grid[0,0]+I.y*mt.grid[1,0]+(I.z*-1)*mt.grid[2,0]
	tmp[1]=I.x*mt.grid[0,1]+I.y*mt.grid[1,1]+(I.z*-1)*mt.grid[2,1]
	tmp[2]=I.x*mt.grid[0,2]+I.y*mt.grid[1,2]+(I.z*-1)*mt.grid[2,2]
	itmp=1.0/sqr(tmp[0]*tmp[0]+tmp[1]*tmp[1]+tmp[2]*tmp[2])
	O.x=tmp[0]*itmp
	O.y=tmp[1]*itmp
	O.z=tmp[2]*itmp
End Method
Method Invert:TMatrix() ' Returns an Inverted Matrix
  Local out:TMatrix = New TMatrix
  Adjoint(out)
  Return out
End Method
Method Adjoint( out:TMatrix Var )
  out.grid[0,0]  =   det3x3(grid[1,1], grid[2,1], grid[3,1], grid[1,2], grid[2,2], grid[3,2], grid[1,3], grid[2,3], grid[3,3])
  out.grid[1,0]  = - det3x3(grid[1,0], grid[2,0], grid[3,0], grid[1,2], grid[2,2], grid[3,2], grid[1,3], grid[2,3], grid[3,3])
  out.grid[2,0]  =   det3x3(grid[1,0], grid[2,0], grid[3,0], grid[1,1], grid[2,1], grid[3,1], grid[1,3], grid[2,3], grid[3,3])
  out.grid[3,0]  = - det3x3(grid[1,0], grid[2,0], grid[3,0], grid[1,1], grid[2,1], grid[3,1], grid[1,2], grid[2,2], grid[3,2])

  out.grid[0,1]  = - det3x3( grid[0,1], grid[2,1], grid[3,1], grid[0,2], grid[2,2], grid[3,2], grid[0,3], grid[2,3], grid[3,3])
  out.grid[1,1]  =   det3x3( grid[0,0], grid[2,0], grid[3,0], grid[0,2], grid[2,2], grid[3,2], grid[0,3], grid[2,3], grid[3,3])
  out.grid[2,1]  = - det3x3( grid[0,0], grid[2,0], grid[3,0], grid[0,1], grid[2,1], grid[3,1], grid[0,3], grid[2,3], grid[3,3])
  out.grid[3,1]  =   det3x3( grid[0,0], grid[2,0], grid[3,0], grid[0,1], grid[2,1], grid[3,1], grid[0,2], grid[2,2], grid[3,2])

  out.grid[0,2]  =   det3x3( grid[0,1], grid[1,1], grid[3,1], grid[0,2], grid[1,2], grid[3,2], grid[0,3], grid[1,3], grid[3,3])
  out.grid[1,2]  = - det3x3( grid[0,0], grid[1,0], grid[3,0], grid[0,2], grid[1,2], grid[3,2], grid[0,3], grid[1,3], grid[3,3])
  out.grid[2,2]  =   det3x3( grid[0,0], grid[1,0], grid[3,0], grid[0,1], grid[1,1], grid[3,1], grid[0,3], grid[1,3], grid[3,3])
  out.grid[3,2]  = - det3x3( grid[0,0], grid[1,0], grid[3,0], grid[0,1], grid[1,1], grid[3,1], grid[0,2], grid[1,2], grid[3,2])
  
  out.grid[0,3]  = - det3x3( grid[0,1], grid[1,1], grid[2,1], grid[0,2], grid[1,2], grid[2,2], grid[0,3], grid[1,3], grid[2,3])
  out.grid[1,3]  =   det3x3( grid[0,0], grid[1,0], grid[2,0], grid[0,2], grid[1,2], grid[2,2], grid[0,3], grid[1,3], grid[2,3])
  out.grid[2,3]  = - det3x3( grid[0,0], grid[1,0], grid[2,0], grid[0,1], grid[1,1], grid[2,1], grid[0,3], grid[1,3], grid[2,3])
  out.grid[3,3]  =   det3x3( grid[0,0], grid[1,0], grid[2,0], grid[0,1], grid[1,1], grid[2,1], grid[0,2], grid[1,2], grid[2,2])
EndMethod
Function det3x3!( a1!, a2!, a3!, b1!, b2!, b3!, c1!, c2!, c3! )
  Local ans!
  ans = a1 * det2x2( b2, b3, c2, c3 )
  ans = ans - b1 * det2x2( a2, a3, c2, c3 )
  ans = ans + c1 * det2x2( a2, a3, b2, b3 )
  Return ans
End Function
Function det2x2!( a!, b!, c!, d!)
  Return a*d-b*c
End Function

This will allow you to convert normals and vectors by an arbitrary matrix and to invert the matrix to do the opposite.