Enable to rotate slice axes.

Assets/VolumeRendering/Scripts/Axis.cs

@@ -0,0 +1,31 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace VolumeRendering
+{
+
+    public class Axis : MonoBehaviour {
+
+        [SerializeField] protected Transform root;
+        [SerializeField] protected float length = 5f;
+
+        protected void OnDrawGizmos()
+        {
+            Gizmos.matrix = Matrix4x4.Rotate(root.rotation) * Matrix4x4.Rotate(transform.rotation).inverse;
+
+            Gizmos.color = Color.red;
+            Gizmos.DrawLine(Vector3.zero, Vector3.right * length);
+
+            Gizmos.color = Color.green;
+            Gizmos.DrawLine(Vector3.zero, Vector3.up * length);
+
+            Gizmos.color = Color.blue;
+            Gizmos.DrawLine(Vector3.zero, Vector3.forward * length);
+        }
+
+    }
+
+}
+
+

Assets/VolumeRendering/Scripts/VolumeRendering.cs

@@ -23,6 +23,7 @@ public class VolumeRendering : MonoBehaviour {
         [Range(0f, 1f)] public float sliceXMin = 0.0f, sliceXMax = 1.0f;
         [Range(0f, 1f)] public float sliceYMin = 0.0f, sliceYMax = 1.0f;
         [Range(0f, 1f)] public float sliceZMin = 0.0f, sliceZMax = 1.0f;
+        public Quaternion axis = Quaternion.identity;
 
         [SerializeField] protected Texture3D volume;
 
@@ -39,6 +40,8 @@ public class VolumeRendering : MonoBehaviour {
             material.SetFloat("_Intensity", intensity);
             material.SetVector("_SliceMin", new Vector3(sliceXMin, sliceYMin, sliceZMin));
             material.SetVector("_SliceMax", new Vector3(sliceXMax, sliceYMax, sliceZMax));
+
+            material.SetMatrix("_AxisRotationMatrix", Matrix4x4.Rotate(axis));
         }
 
         Mesh Build() {

Assets/VolumeRendering/Scripts/VolumeRenderingController.cs

@@ -11,6 +11,7 @@ public class VolumeRenderingController : MonoBehaviour {
 
         [SerializeField] protected VolumeRendering volume;
         [SerializeField] protected Slider sliderXMin, sliderXMax, sliderYMin, sliderYMax, sliderZMin, sliderZMax;
+        [SerializeField] protected Transform axis;
 
         void Start ()
         {
@@ -38,6 +39,11 @@ void Start ()
             });
         }
 
+        void Update()
+        {
+            volume.axis = axis.rotation;
+        }
+
         public void OnIntensity(float v)
         {
             volume.intensity = v;

Assets/VolumeRendering/Shaders/VolumeRendering.cginc

@@ -0,0 +1,145 @@
+#ifndef __VOLUME_RENDERING_INCLUDED__
+#define __VOLUME_RENDERING_INCLUDED__
+
+#include "UnityCG.cginc"
+
+#ifndef ITERATIONS
+#define ITERATIONS 100
+#endif
+
+half4 _Color;
+sampler3D _Volume;
+half _Intensity, _Threshold;
+half3 _SliceMin, _SliceMax;
+float4x4 _AxisRotationMatrix;
+
+struct Ray {
+  float3 origin;
+  float3 dir;
+};
+
+struct AABB {
+  float3 min;
+  float3 max;
+};
+
+bool intersect(Ray r, AABB aabb, out float t0, out float t1)
+{
+  float3 invR = 1.0 / r.dir;
+  float3 tbot = invR * (aabb.min - r.origin);
+  float3 ttop = invR * (aabb.max - r.origin);
+  float3 tmin = min(ttop, tbot);
+  float3 tmax = max(ttop, tbot);
+  float2 t = max(tmin.xx, tmin.yz);
+  t0 = max(t.x, t.y);
+  t = min(tmax.xx, tmax.yz);
+  t1 = min(t.x, t.y);
+  return t0 <= t1;
+}
+
+float3 localize(float3 p) {
+  return mul(unity_WorldToObject, float4(p, 1)).xyz;
+}
+
+float3 get_uv(float3 p) {
+  // float3 local = localize(p);
+  return (p + 0.5);
+}
+
+float sample_volume(float3 uv, float3 p)
+{
+  float v = tex3D(_Volume, uv).r * _Intensity;
+
+  float3 axis = mul(_AxisRotationMatrix, float4(p, 0)).xyz;
+  axis = get_uv(axis);
+  float min = step(_SliceMin.x, axis.x) * step(_SliceMin.y, axis.y) * step(_SliceMin.z, axis.z);
+  float max = step(axis.x, _SliceMax.x) * step(axis.y, _SliceMax.y) * step(axis.z, _SliceMax.z);
+
+  return v * min * max;
+}
+
+bool outside(float3 uv)
+{
+  const float EPSILON = 0.01;
+  float lower = -EPSILON;
+  float upper = 1 + EPSILON;
+  return (
+			uv.x < lower || uv.y < lower || uv.z < lower ||
+			uv.x > upper || uv.y > upper || uv.z > upper
+		);
+}
+
+struct appdata
+{
+  float4 vertex : POSITION;
+  float2 uv : TEXCOORD0;
+};
+
+struct v2f
+{
+  float4 vertex : SV_POSITION;
+  float2 uv : TEXCOORD0;
+  float3 world : TEXCOORD1;
+};
+
+v2f vert(appdata v)
+{
+  v2f o;
+  o.vertex = UnityObjectToClipPos(v.vertex);
+  o.uv = v.uv;
+  o.world = mul(unity_ObjectToWorld, v.vertex).xyz;
+  return o;
+}
+
+fixed4 frag(v2f i) : SV_Target
+{
+  Ray ray;
+  ray.origin = localize(i.world);
+
+  // world space direction to object space
+  float3 dir = normalize(i.world - _WorldSpaceCameraPos);
+  ray.dir = normalize(mul((float3x3) unity_WorldToObject, dir));
+
+  AABB aabb;
+  aabb.min = float3(-0.5, -0.5, -0.5);
+  aabb.max = float3(0.5, 0.5, 0.5);
+
+  float tnear;
+  float tfar;
+  intersect(ray, aabb, tnear, tfar);
+
+  tnear = max(0.0, tnear);
+
+  // float3 start = ray.origin + ray.dir * tnear;
+  float3 start = ray.origin;
+  float3 end = ray.origin + ray.dir * tfar;
+  float dist = abs(tfar - tnear); // float dist = distance(start, end);
+  float step_size = dist / float(ITERATIONS);
+  float3 ds = normalize(end - start) * step_size;
+
+  float4 dst = float4(0, 0, 0, 0);
+  float3 p = start;
+
+  [unroll]
+  for (int iter = 0; iter < ITERATIONS; iter++)
+  {
+    float3 uv = get_uv(p);
+    float v = sample_volume(uv, p);
+    float4 src = float4(v, v, v, v);
+    src.a *= 0.5;
+    src.rgb *= src.a;
+
+    // blend
+    dst = (1.0 - dst.a) * src + dst;
+    p += ds;
+
+    if (dst.a > _Threshold)
+    {
+      break;
+    }
+  }
+
+  return saturate(dst) * _Color;
+}
+
+#endif 

Assets/VolumeRendering/Shaders/VolumeRendering.shader

@@ -12,83 +12,6 @@
 
 	CGINCLUDE
 
-	half4 _Color;
-	sampler3D _Volume;
-	half _Intensity, _Threshold;
-	half3 _SliceMin, _SliceMax;
-
-	struct Ray {
-		float3 origin;
-		float3 dir;
-	};
-
-	struct AABB {
-		float3 min;
-		float3 max;
-	};
-
-	bool intersect(Ray r, AABB aabb, out float t0, out float t1)
-	{
-		float3 invR = 1.0 / r.dir;
-		float3 tbot = invR * (aabb.min - r.origin);
-		float3 ttop = invR * (aabb.max - r.origin);
-		float3 tmin = min(ttop, tbot);
-		float3 tmax = max(ttop, tbot);
-		float2 t = max(tmin.xx, tmin.yz);
-		t0 = max(t.x, t.y);
-		t = min(tmax.xx, tmax.yz);
-		t1 = min(t.x, t.y);
-		return t0 <= t1;
-	}
-
-	float3 localize(float3 p) {
-		return mul(unity_WorldToObject, float4(p, 1)).xyz;
-	}
-
-	float3 get_uv(float3 p) {
-		// float3 local = localize(p);
-		return (p + 0.5);
-	}
-
-	float sample_volume(float3 uv) {
-		float v = tex3D(_Volume, uv).r * _Intensity;
-		float min = step(_SliceMin.x, uv.x) * step(_SliceMin.y, uv.y) * step(_SliceMin.z, uv.z);
-		float max = step(uv.x, _SliceMax.x) * step(uv.y, _SliceMax.y) * step(uv.z, _SliceMax.z);
-		return v * min * max;
-	}
-
-	bool outside(float3 uv) {
-		const float EPSILON = 0.01;
-		float lower = -EPSILON;
-		float upper = 1 + EPSILON;
-		return (
-			uv.x < lower || uv.y < lower || uv.z < lower ||
-			uv.x > upper || uv.y > upper || uv.z > upper
-		);
-	}
-
-	struct appdata
-	{
-		float4 vertex : POSITION;
-		float2 uv : TEXCOORD0;
-	};
-
-	struct v2f
-	{
-		float4 vertex : SV_POSITION;
-		float2 uv : TEXCOORD0;
-		float3 world : TEXCOORD1;
-	};
-
-	v2f vert(appdata v)
-	{
-		v2f o;
-		o.vertex = UnityObjectToClipPos(v.vertex);
-		o.uv = v.uv;
-		o.world = mul(unity_ObjectToWorld, v.vertex).xyz;
-		return o;
-	}
-
 	ENDCG
 
 	SubShader {
@@ -99,60 +22,12 @@
 		Pass
 		{
 			CGPROGRAM
+
+      #define ITERATIONS 100
+			#include "./VolumeRendering.cginc"
 			#pragma vertex vert
 			#pragma fragment frag
 
-			#define COUNT 100
-
-			fixed4 frag (v2f i) : SV_Target
-			{
-				Ray ray;
-				ray.origin = localize(i.world);
-
-				// world space direction to object space
-				float3 dir = normalize(i.world - _WorldSpaceCameraPos);
-				ray.dir = normalize(mul((float3x3)unity_WorldToObject, dir));
-
-				AABB aabb;
-				aabb.min = float3(-0.5, -0.5, -0.5);
-				aabb.max = float3( 0.5,  0.5,  0.5);
-
-				float tnear;
-				float tfar;
-				intersect(ray, aabb, tnear, tfar);
-
-				tnear = max(0.0, tnear);
-
-				// float3 start = ray.origin + ray.dir * tnear;
-				float3 start = ray.origin;
-				float3 end = ray.origin + ray.dir * tfar; 
-				float dist = abs(tfar - tnear); // float dist = distance(start, end);
-				float step_size = dist / float(COUNT);
-				float3 ds = normalize(end - start) * step_size;
-
-				float4 dst = float4(0, 0, 0, 0);
-				float3 p = start;
-
-				[unroll]
-				for (int iter = 0; iter < COUNT; iter++) {
-					float3 uv = get_uv(p);
-					float v = sample_volume(uv);
-					float4 src = float4(v, v, v, v);
-					src.a *= 0.5;
-					src.rgb *= src.a;
-
-					// blend
-					dst = (1.0 - dst.a) * src + dst;
-					p += ds;
-
-					if (dst.a > _Threshold) {
-						break;
-					}
-				}
-
-				return saturate(dst) * _Color;
-			}
-
 			ENDCG
 		}
 	}

ProjectSettings/ProjectVersion.txt

@@ -1 +1 @@
-m_EditorVersion: 2017.2.0f3
+m_EditorVersion: 2017.3.1f1