修改静态资源文件夹位置

public/sdk/three/jsm/libs/surfaceNet.js

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+/**
+ * SurfaceNets in JavaScript
+ *
+ * Written by Mikola Lysenko (C) 2012
+ *
+ * MIT License
+ *
+ * Based on: S.F. Gibson, 'Constrained Elastic Surface Nets'. (1998) MERL Tech Report.
+ * from https://github.com/mikolalysenko/isosurface/tree/master
+ * 
+ */
+
+let surfaceNet = ( dims, potential, bounds ) => {
+		
+	
+	//Precompute edge table, like Paul Bourke does.
+	// This saves a bit of time when computing the centroid of each boundary cell
+	var cube_edges = new Int32Array(24) , edge_table = new Int32Array(256);
+	(function() {
+
+		//Initialize the cube_edges table
+		// This is just the vertex number of each cube
+		var k = 0;
+		for(var i=0; i<8; ++i) {
+			for(var j=1; j<=4; j<<=1) {
+				var p = i^j;
+				if(i <= p) {
+					cube_edges[k++] = i;
+					cube_edges[k++] = p;
+				}
+			}
+		}
+
+		//Initialize the intersection table.
+		//  This is a 2^(cube configuration) ->  2^(edge configuration) map
+		//  There is one entry for each possible cube configuration, and the output is a 12-bit vector enumerating all edges crossing the 0-level.
+		for(var i=0; i<256; ++i) {
+			var em = 0;
+			for(var j=0; j<24; j+=2) {
+				var a = !!(i & (1<<cube_edges[j]))
+					, b = !!(i & (1<<cube_edges[j+1]));
+				em |= a !== b ? (1 << (j >> 1)) : 0;
+			}
+			edge_table[i] = em;
+		}
+	})();
+
+	//Internal buffer, this may get resized at run time
+	var buffer = new Array(4096);
+	(function() {
+		for(var i=0; i<buffer.length; ++i) {
+			buffer[i] = 0;
+		}
+	})();
+
+	if(!bounds) {
+		bounds = [[0,0,0],dims];
+	}
+	
+	var scale     = [0,0,0];
+	var shift     = [0,0,0];
+	for(var i=0; i<3; ++i) {
+		scale[i] = (bounds[1][i] - bounds[0][i]) / dims[i];
+		shift[i] = bounds[0][i];
+	}
+	
+	var vertices = []
+		, faces = []
+		, n = 0
+		, x = [0, 0, 0]
+		, R = [1, (dims[0]+1), (dims[0]+1)*(dims[1]+1)]
+		, grid = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
+		, buf_no = 1;
+	
+		
+	//Resize buffer if necessary 
+	if(R[2] * 2 > buffer.length) {
+		var ol = buffer.length;
+		buffer.length = R[2] * 2;
+		while(ol < buffer.length) {
+			buffer[ol++] = 0;
+		}
+	}
+	
+	//March over the voxel grid
+	for(x[2]=0; x[2]<dims[2]-1; ++x[2], n+=dims[0], buf_no ^= 1, R[2]=-R[2]) {
+	
+		//m is the pointer into the buffer we are going to use.  
+		//This is slightly obtuse because javascript does not have good support for packed data structures, so we must use typed arrays :(
+		//The contents of the buffer will be the indices of the vertices on the previous x/y slice of the volume
+		var m = 1 + (dims[0]+1) * (1 + buf_no * (dims[1]+1));
+		
+		for(x[1]=0; x[1]<dims[1]-1; ++x[1], ++n, m+=2)
+		for(x[0]=0; x[0]<dims[0]-1; ++x[0], ++n, ++m) {
+		
+			//Read in 8 field values around this vertex and store them in an array
+			//Also calculate 8-bit mask, like in marching cubes, so we can speed up sign checks later
+			var mask = 0, g = 0;
+			for(var k=0; k<2; ++k)
+			for(var j=0; j<2; ++j)      
+			for(var i=0; i<2; ++i, ++g) {
+				var p = potential(
+					scale[0]*(x[0]+i)+shift[0],
+					scale[1]*(x[1]+j)+shift[1],
+					scale[2]*(x[2]+k)+shift[2]);
+				grid[g] = p;
+				mask |= (p < 0) ? (1<<g) : 0;
+			}
+			
+			//Check for early termination if cell does not intersect boundary
+			if(mask === 0 || mask === 0xff) {
+				continue;
+			}
+			
+			//Sum up edge intersections
+			var edge_mask = edge_table[mask]
+				, v = [0.0,0.0,0.0]
+				, e_count = 0;
+				
+			//For every edge of the cube...
+			for(var i=0; i<12; ++i) {
+			
+				//Use edge mask to check if it is crossed
+				if(!(edge_mask & (1<<i))) {
+					continue;
+				}
+				
+				//If it did, increment number of edge crossings
+				++e_count;
+				
+				//Now find the point of intersection
+				var e0 = cube_edges[ i<<1 ]       //Unpack vertices
+					, e1 = cube_edges[(i<<1)+1]
+					, g0 = grid[e0]                 //Unpack grid values
+					, g1 = grid[e1]
+					, t  = g0 - g1;                 //Compute point of intersection
+				if(Math.abs(t) > 1e-6) {
+					t = g0 / t;
+				} else {
+					continue;
+				}
+				
+				//Interpolate vertices and add up intersections (this can be done without multiplying)
+				for(var j=0, k=1; j<3; ++j, k<<=1) {
+					var a = e0 & k
+						, b = e1 & k;
+					if(a !== b) {
+						v[j] += a ? 1.0 - t : t;
+					} else {
+						v[j] += a ? 1.0 : 0;
+					}
+				}
+			}
+			
+			//Now we just average the edge intersections and add them to coordinate
+			var s = 1.0 / e_count;
+			for(var i=0; i<3; ++i) {
+				v[i] = scale[i] * (x[i] + s * v[i]) + shift[i];
+			}
+			
+			//Add vertex to buffer, store pointer to vertex index in buffer
+			buffer[m] = vertices.length;
+			vertices.push(v);
+			
+			//Now we need to add faces together, to do this we just loop over 3 basis components
+			for(var i=0; i<3; ++i) {
+				//The first three entries of the edge_mask count the crossings along the edge
+				if(!(edge_mask & (1<<i)) ) {
+					continue;
+				}
+				
+				// i = axes we are point along.  iu, iv = orthogonal axes
+				var iu = (i+1)%3
+					, iv = (i+2)%3;
+					
+				//If we are on a boundary, skip it
+				if(x[iu] === 0 || x[iv] === 0) {
+					continue;
+				}
+				
+				//Otherwise, look up adjacent edges in buffer
+				var du = R[iu]
+					, dv = R[iv];
+				
+				//Remember to flip orientation depending on the sign of the corner.
+				if(mask & 1) {
+					faces.push([buffer[m],    buffer[m-du],    buffer[m-dv]]);
+					faces.push([buffer[m-dv], buffer[m-du],    buffer[m-du-dv]]);
+				} else {
+					faces.push([buffer[m],    buffer[m-dv],    buffer[m-du]]);
+					faces.push([buffer[m-du], buffer[m-dv],    buffer[m-du-dv]]);
+				}
+			}
+		}
+	}
+	
+	//All done!  Return the result
+	return { positions: vertices, cells: faces };
+}
+
+export { surfaceNet }