Question Extracting mesh rotation from unity_ObjectToWorld

Hi,

I am trying to get the rotation angle of the mesh while in the fragment shader. Currently, I've got the following code to try and get these values using the unity_ObjectToWorld which I've got redefined as UNITY_MATRIX_M.

Code (CSharp):

1. float objectRotation_y = degrees(asin(UNITY_MATRIX_M._m03));
2. float objectRotation_z = degrees(asin(UNITY_MATRIX_M._m01))/(-1*cos(radians(objectRotation_y)));
3. float objectRotation_x = degrees(-1*asin(UNITY_MATRIX_M._m12))/cos(radians(objectRotation_y));
4.  

Currently it the these variables are returning nothing at all which I figured out is something to do with the asin function where it only takes values between -PI/2 and PI/2. However when I go

Code (CSharp):

1. float objectRotation_y = degrees(asin(UNITY_MATRIX_M._m03 % PI/2));

it still returns nothing unless I go above UNITY_MATRIX_M._m03 % PI/2.1.

Am I going in the right direction to get the mesh rotation? I know I could easily get this information by either using a compute buffer or setting a material property via script. But I'm not sure which would be the most efficient. Also, is there some documentation about the value ranges of the elements in the unity_ObjectToWorld matrix?

TIA

 

Yep, those won’t get you anything remotely close to the values you want. Search Google for “matrix to Euler” and look for something that uses

atan2()

.

 

thanks, I got it working now