Added trilinear interpolation to VolumeColormaker

src/color/volume-colormaker.js

@@ -6,11 +6,11 @@
 
 
 import { Vector3 } from "../../lib/three.es6.js";
+import { lerp } from "../math/math-utils.js";
 
 import { ColormakerRegistry } from "../globals.js";
 import Colormaker from "./colormaker.js";
 
-
 /**
  * Color by volume position
  */
@@ -29,17 +29,57 @@ class VolumeColormaker extends Colormaker{
             var data = volume.data;
             var nx = volume.nx;
             var ny = volume.ny;
+            var nxy = nx * ny;
             var vec = new Vector3();
 
             this.positionColor = function( coords ){
 
                 vec.copy( coords );
                 vec.applyMatrix4( inverseMatrix );
-                vec.round();
-
-                var index = ( ( ( ( vec.z * ny ) + vec.y ) * nx ) + vec.x );
 
-                return valueScale( data[ index ] );
+                // Trilinear interpolation test
+                var x0 = Math.floor( vec.x );
+                var y0 = Math.floor( vec.y );
+                var z0 = Math.floor( vec.z );
+
+                // Indices
+                var i = ( ( ( ( z0 * ny ) + y0 ) * nx ) + x0 );
+                var i1 = i + 1;
+                var iy = i + nx;
+                var iz = i + nxy;
+                var i1y = iy + 1;
+                var i1z = iz + 1;
+                var iyz = iy + nxy;
+                var i1yz = iyz + 1;
+
+                // Values
+                var v = data[ i ];
+                var v1 = data[ i1 ];
+                var vy = data[ iy ];
+                var vz = data[ iz ];
+                var v1y = data[ i1y ];
+                var v1z = data[ i1z ];
+                var vyz = data[ iyz ];
+                var v1yz = data[ i1yz ];
+
+                var xd = vec.x - x0;
+                var yd = vec.y - y0;
+                var zd = vec.z - z0;
+
+                var c00 = lerp( v, v1, xd );
+                var c01 = lerp( vz, v1z, xd );
+                var c10 = lerp( vy, v1y, xd );
+                var c11 = lerp( vyz, v1yz, xd );
+
+                var c0 = lerp( c00, c10, yd );
+                var c1 = lerp( c01, c11, yd );
+                var c = lerp( c0, c1, zd );
+
+                return valueScale( c );
+
+                //vec.round();
+                //var index = ( ( ( ( vec.z * ny ) + vec.y ) * nx ) + vec.x );
+                //return valueScale( data[ index ] );
 
             };