Best way to get object rotation

I am attemting an unlit shader that color tints an object depending on its relation to the world axis. As an example, any normals of a rotating object facing the world-x axis would get tinted with agreen color.

1. Is there any optimized way to get the world rotation from within the shader?

2. Would it be better/(more optimized) to supply it as a parameter through code to the shader?

 

Sounds like you don't need a shader, you just need a script that modifies the objects material based on its rotation.

 

example in shader

Code (CSharp):

1. Properties {
2. _RotationSpeed ("Rotation Speed", Float) = 2.0  
3. }
4.  
5.      float sinX = sin ( _RotationSpeed * _Time );
6.  
7.             float cosX = cos ( _RotationSpeed * _Time );
8.  
9.             float sinY = sin ( _RotationSpeed * _Time );
10.  
11.             float2x2 rotationMatrix = float2x2( cosX, -sinX, sinY, cosX);
12. }

example : JS script :

Code (JavaScript):

1. var scrollSpeed = 0.90;
2. var scrollSpeed2 = 0.90;
3. function FixedUpdate()
4. {
5. var offset = Time.time * scrollSpeed;
6. var offset2 = Time.time * scrollSpeed2;
7. renderer.material.mainTextureOffset = Vector2 (offset2,-offset);
8.  
9. }

 

@GGeff: If I was not dependent on the objects normals, a script would work. I think I would avoid iterating through all those meshes normals in script if I can put that work on the gpu instead.

@Niko-belik: Thanks, but not quite what I am looking for. I need some way to get the rotation relation between the vertex normal and the world axis.

 

Aha! Found what I was looking for, and ironically it brought me back to where I first started, with _Object2World. The reason it did not work before was the order:

Code (CSharp):

1.  
2. //correct:
3. normalize(mul((float3x3)_Object2World, i.normal).xyz);
4.  
5. //incorrect:
6. normalize(mul(i.normal, ((float3x3)_Object2World).xyz);
7.  

The effect was that I no longer got the proper rotation of the normal if I had the wrong order. I hope anyone following in my footsteps can benifit from this.