Matrix in Houdini

  Matrix in houdini is still just a collection of numbers, the only different is :How you apply this data determines what kind of matrix it is.

  There is always 3x3 or 4x4 or QxQ matrix in houdini.

0.3x3 Matrix is:

 

1.Main type of matrix in houdini.

2.If you want to rotate some points using matrix......

3.If you want to translate something......

The meaning of this matrix is:

 

 4.Identity matrix is a matrix which keeps your positions the same

 5.Example rotate geometry using wrangle node.

.In the wrangle node ,the vex script is:

1 //create a identity matrix 'rotY'
2 matrix3 rotY = ident();
3 
4 //Applies a rotation value to the given matrix, here is rotY.
5 //Channel 'rotY_value' is the rotation degree.
6 rotate(rotY, radians(chf('rotY_value')), {0,1,0});
7 
8 @P *= rotY;

6. Set a component of a matrix.

. We can use 'setcomp' in VEX to modify a single component of a exist matrix.

 

X.* is the X Axis direction vector of this Axis.

Y.*  is the Y Axis direction vector of this Axis.

Z.*   is the Z Axis direction vector of this Axis.

P.* is the position of this Axis.