How to Calculate a 3x3 Rotation Matrix around a Given Axis?

In summary, the conversation discusses finding a 3x3 matrix R to represent a rotation of Pi/6 around the axis of rotation v={1, 2, 3}. The direction of rotation and starting point of the axis are uncertain. Links are provided for further assistance.
  • #1
yanyin
21
0
Hi, if i want to find a 3x3 matrix R which represents a rotation of Pi/6 around the axis of rotation v(vector)={1, 2, 3}. how can i find it?
 
Last edited:
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  • #2
Are you saying that your axis is along a vector that starts at the origin of the coordinate system and has its tip at the point (x,y,z)=(1,2,3)? And is your rotation direction clockwise or counterclockwise as viewed from the perspective of (0,0,0)?
 
  • #3
Originally posted by Janitor
Are you saying that your axis is along a vector that starts at the origin of the coordinate system and has its tip at the point (x,y,z)=(1,2,3)? And is your rotation direction clockwise or counterclockwise as viewed from the perspective of (0,0,0)?
Thanks. it's a vector from origin to (1, 2, 3). which direction? i am not sure yet. let say clockwise.
 
  • #4
Start by figuring out what the result of rotating
[0,0,1]
[0,1,0]
and
[1,0,0]
are.

Once you've done that, you shouldn't have any trouble making hte matrix.
 

1. How do you find a 3x3 rotation matrix?

To find a 3x3 rotation matrix, you can use the basic formula for a rotation matrix in 3D space:
R = [cosθ -sinθ 0
sinθ cosθ 0
0 0 1]
where θ is the angle of rotation. This formula can be modified for different axes of rotation or to rotate around a specific point.

2. What is the purpose of a 3x3 rotation matrix?

A 3x3 rotation matrix is used to represent and perform rotations in 3D space. It is commonly used in computer graphics, robotics, and other fields where 3D rotations need to be calculated and applied.

3. How do you multiply two 3x3 rotation matrices?

To multiply two 3x3 rotation matrices, you can use the matrix multiplication formula:
[R1] x [R2] = [R]
where R1 and R2 are the two rotation matrices and R is the resulting matrix. Note that the order of multiplication matters, as matrix multiplication is not commutative.

4. Can a 3x3 rotation matrix be used for scaling or translation?

No, a 3x3 rotation matrix is only used for rotation in 3D space. Scaling and translation are represented by different types of matrices.

5. How many degrees of freedom does a 3x3 rotation matrix have?

A 3x3 rotation matrix has 3 degrees of freedom, as it can represent rotations around the x, y, and z axes. This means that it can represent any rotation in 3D space using just 3 parameters.

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