Inverse of view matrix(right-handed look-at matrix) for pick

[cymx2]

I need Inverse of view matrix (right-handed look-at matrix) for screen pick,but irrlicht's matrix only have matrix4::buildCameraLookAtMatrixRH(),no it's inverse matrix. so I write a inverse matrix,is right??

(*this)(0,0) = xaxis.X;
(*this)(1,0) = xaxis.Y;
(*this)(2,0) = xaxis.Z;
(*this)(3,0) = 0;

(*this)(0,1) = yaxis.X;
(*this)(1,1) = yaxis.Y;
(*this)(2,1) = yaxis.Z;
(*this)(3,1) = 0;

(*this )(0,2) = zaxis.X;
(*this)(1,2) = zaxis.Y;
(*this)(2,2) = zaxis.Z;
(*this)(3,2) = 0;

(*this)(0,3) = position;
(*this)(1,3) = position;
(*this)(2,3) = position;
(*this)(3,3) = 1.0f;

CameraLookAtMatrixRH=M(xaxis,yaxis,zaxis)*M(-position)
so Inverse(CameraLookAtMatrixRH)=M(position)*T(M(xaxis,yaxis,zaxis))

over is right???

[needforhint]

why don't you use inverse() method of matrix class????

[Baal Cadar]

Use either matrix4::makeInverse() or matrix4::getInverse(). What you tried to do yourself is not the inverse of a matrix, but the transpose, which is not the same. inverse is much more difficult and expensive to compute and by no means the same.

[cymx2]

M(xaxis,yaxis,zaxis) * Inverse（M(xaxis,yaxis,zaxis)）=E
M(xaxis,yaxis,zaxis) * Transpose(M(xaxis,yaxis,zaxis) )=E
so:
Inverse（M(xaxis,yaxis,zaxis)）=Transpose(M(xaxis,yaxis,zaxis) )

CameraLookAtMatrixRH=M(xaxis,yaxis,zaxis)*M(-position) (right multiply)

so:
Inverse(CameraLookAtMatrixRH)=M(position)*Transpose(M(xaxis,yaxis,zaxis))

I think I am right,I multiply the two matrix-----M(xaxis,yaxis,zaxis)*M(-position) and M(position)*Transpose(M(xaxis,yaxis,zaxis)) ,result is rihgt!

matrix4::makeInverse() is too slow，view matrix is often change

[elander]

I realy don't undertstand much of view matrices yet (still have to revise this subject) but there are situtations where the inverse calculation can be simplified by using the transpose.