Best way to get object rotation

Unity Engine
1

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?

2

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

3

example in shader

Properties {
_RotationSpeed ("Rotation Speed", Float) = 2.0  
}

     float sinX = sin ( _RotationSpeed * _Time );

            float cosX = cos ( _RotationSpeed * _Time );

            float sinY = sin ( _RotationSpeed * _Time );

            float2x2 rotationMatrix = float2x2( cosX, -sinX, sinY, cosX);
}

example : JS script :

var scrollSpeed = 0.90;
var scrollSpeed2 = 0.90;
function FixedUpdate()
{
var offset = Time.time * scrollSpeed;
var offset2 = Time.time * scrollSpeed2;
renderer.material.mainTextureOffset = Vector2 (offset2,-offset);

}
4

@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.

@ -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.

5

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:

//correct:
normalize(mul((float3x3)_Object2World, i.normal).xyz);

//incorrect:
normalize(mul(i.normal, ((float3x3)_Object2World).xyz);

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.