Cleaned up SliceRenderingShader.shader. Also added manual clamping of data texture coordinates (since Unity doens't seem to support clamp to custom border value). This should fix artifacts when moving the slicing plane object.

Author: mlavik1

Assets/Shaders/SliceRenderingShader.shader

@@ -36,29 +36,40 @@ Shader "VolumeRendering/SliceRenderingShader"
 
             sampler3D _DataTex;
             sampler2D _TFTex;
+            // Parent's inverse transform (used to convert from world space to volume space)
             uniform float4x4 _parentInverseMat;
+            // Plane transform
             uniform float4x4 _planeMat;
 
             v2f vert (appdata v)
             {
                 v2f o;
-                float3 vert = float3(-v.uv.x, 0.0f, -v.uv.y) + float3(0.5f, 0.0f, 0.5f);
-                vert = mul(_planeMat, float4(vert, 1.0f));
-                //o.vertex = mul(UNITY_MATRIX_VP, float4(vert, 1.0f));
-                o.vertex = UnityObjectToClipPos(v.vertex);;
+                o.vertex = UnityObjectToClipPos(v.vertex);
+                // Calculate plane vertex world position.
+                float3 vert = mul(_planeMat, float4(0.5f -v.uv.x, 0.0f, 0.5f -v.uv.y, 1.0f));
+                // Convert from world space to volume space.
                 o.relVert = mul(_parentInverseMat, float4(vert, 1.0f));
                 o.uv = v.uv;
                 return o;
             }
 
             fixed4 frag (v2f i) : SV_Target
             {
-                float3 dataCoord = i.relVert +float3(0.5f, 0.5f, 0.5f);
-                float dataVal = tex3D(_DataTex, dataCoord);
-                float4 col = tex2D(_TFTex, float2(dataVal, 0.0f));
-                col.a = 1.0f;
-
-                return col;
+                float3 dataCoord = i.relVert + float3(0.5f, 0.5f, 0.5f);
+                // If the current fragment is outside the volume, simply colour it black.
+                // Note: Unity does not seem to have support for clamping texture coordinates to a border value, so we have to do this manually
+                if (dataCoord.x > 1.0f || dataCoord.y > 1.0f || dataCoord.z > 1.0f || dataCoord.x < 0.0f || dataCoord.y < 0.0f || dataCoord.z < 0.0f)
+                {
+                   return float4(0.0f, 0.0f, 0.0f, 1.0f);
+                }
+                else
+                {
+                   // Sample the volume texture.
+                   float dataVal = tex3D(_DataTex, dataCoord);
+                   float4 col = tex2D(_TFTex, float2(dataVal, 0.0f));
+                   col.a = 1.0f;
+                   return col;
+                }
             }
             ENDCG
         }