QuaternionTest.shader

Shader "Custom/QuaternionTest" {
	Properties {
		_AX("axis", Vector) = (0,0,0,0)
		_TH("theta", Float) = 0
	}
 
	CGINCLUDE
		#include "UnityCG.cginc"
		#define PI 3.1416
		
		float4 _AX;
		float _TH;
		
		struct v2f {
			float4 pos : SV_POSITION;
			fixed4 color : COLOR;
		};
		
        // Quaternion multiplication.
        // http://mathworld.wolfram.com/Quaternion.html
        float4 qmul(float4 q1, float4 q2)
        {
            return float4(
                q2.xyz * q1.w + q1.xyz * q2.w + cross(q1.xyz, q2.xyz),
                q1.w * q2.w - dot(q1.xyz, q2.xyz)
            );
        }

        // Rotate a vector with a rotation quaternion.
        // http://mathworld.wolfram.com/Quaternion.html
        float3 rotate_vector(float3 v, float4 r)
        {
            float4 r_c = r * float4(-1, -1, -1, 1);
            return qmul(r, qmul(float4(v, 0), r_c)).xyz;
        }
		
		float3 rotate(float3 v, float3 axis, float theta){
			axis = normalize(axis);
			float s,c;
			sincos(theta,s,c);
			float4
				q = float4(axis.x*s,axis.y*s,axis.z*s,c);
			
			return rotate_vector(v,q);
		}
 
		v2f vert (appdata_full v)
		{
			float3 axis = normalize(_AX.xyz);
			float theta = PI * _TH;
			v.vertex.xyz = rotate(v.vertex.xyz, axis, theta);
			
			v2f o;
			o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
			o.color = v.color;
			return o;
		}
			
		half4 frag (v2f i) : COLOR
		{
			return i.color;
		}
	ENDCG
	
	SubShader {
		Pass {
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma fragmentoption ARB_precision_hint_fastest
			ENDCG 
		}
	}
}

QuaternionTest2.shader

Shader "Custom/QuaternionTest2" {
	Properties {
		_AX("axis", Vector) = (0,0,0,0)
		_TH("theta", Float) = 0
		_Q("quaternion", Vector) = (0,0,0,1)
	}
 
	CGINCLUDE
		#include "UnityCG.cginc"
		#define PI 3.1416
		
		float4 _AX,_Q;
		float _TH;
		
		struct v2f {
			float4 pos : SV_POSITION;
			fixed4 color : COLOR;
		};
		
        // Quaternion multiplication.
        // http://mathworld.wolfram.com/Quaternion.html
        float4 qmul(float4 q1, float4 q2)
        {
            return float4(
                q2.xyz * q1.w + q1.xyz * q2.w + cross(q1.xyz, q2.xyz),
                q1.w * q2.w - dot(q1.xyz, q2.xyz)
            );
        }

        // Rotate a vector with a rotation quaternion.
        // http://mathworld.wolfram.com/Quaternion.html
        float3 rotate_vector(float3 v, float4 r)
        {
            float4 r_c = r * float4(-1, -1, -1, 1);
            return qmul(r, qmul(float4(v, 0), r_c)).xyz;
        }
		
		float3 rotate(float3 v, float3 axis, float theta){
			axis = normalize(axis);
			float s,c;
			sincos(theta,s,c);
			float4
				q = float4(axis.x*s,axis.y*s,axis.z*s,c);
			
			return rotate_vector(v,q);
		}
 
		v2f vert (appdata_full v)
		{
			float3 axis = normalize(_AX.xyz);
			float theta = PI * _TH;
			
			v.vertex.xyz = rotate_vector(v.vertex.xyz, _Q);
			
			v2f o;
			o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
			o.color = v.color;
			return o;
		}
			
		half4 frag (v2f i) : COLOR
		{
			return i.color;
		}
	ENDCG
	
	SubShader {
		Pass {
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma fragmentoption ARB_precision_hint_fastest
			ENDCG 
		}
	}
}

QuaternionTest3.shader

Shader "Custom/QuaternionTest3" {
	Properties {
		_LA ("look at", Vector) = (0,0,0,1)
		_T ("t",Float) = 0
	}
 
	CGINCLUDE
		#include "UnityCG.cginc"
		#define PI 3.1416
		
		float4 _LA;
		float _T;
		
		struct v2f {
			float4 pos : SV_POSITION;
			fixed4 color : COLOR;
		};
		
        // Quaternion multiplication.
        // http://mathworld.wolfram.com/Quaternion.html
        float4 qmul(float4 q1, float4 q2)
        {
            return float4(
                q2.xyz * q1.w + q1.xyz * q2.w + cross(q1.xyz, q2.xyz),
                q1.w * q2.w - dot(q1.xyz, q2.xyz)
            );
        }

        // Rotate a vector with a rotation quaternion.
        // http://mathworld.wolfram.com/Quaternion.html
        float3 rotate_vector(float3 v, float4 r)
        {
            float4 r_c = r * float4(-1, -1, -1, 1);
            return qmul(r, qmul(float4(v, 0), r_c)).xyz;
        }
		
		float3 rotate(float3 v, float3 axis, float theta){
			axis = normalize(axis);
			float s,c;
			sincos(theta,s,c);
			float4
				q = float4(axis.x*s,axis.y*s,axis.z*s,c);
			
			return rotate_vector(v,q);
		}
 
		v2f vert (appdata_full v)
		{
			float3
				v1 = float3(0,0,1),
				v2 = normalize(_LA.xyz),
				cr = cross(v1,v2);
			float4 q = float4( cr,1+dot(v1,v2) );
			q = normalize(lerp(float4(0,0,0,1),q,saturate(_T)));
			
			v.vertex.xyz = rotate_vector(v.vertex.xyz, q).xyz;
			
			v2f o;
			o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
			o.color = v.color;
			return o;
		}
			
		half4 frag (v2f i) : COLOR
		{
			return i.color;
		}
	ENDCG
	
	SubShader {
		Pass {
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma fragmentoption ARB_precision_hint_fastest
			ENDCG 
		}
	}
}