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// Copyright 2017 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
/**
* @fileoverview Helper class implementing various utilities for THREE.js
* geometry.
*/
function GeometryHelper() {}
GeometryHelper.prototype = {
constructor: GeometryHelper,
// Computes vertex normals on THREE.js buffer geometry, even when the mesh
// uses triangle strip connectivity.
computeVertexNormals: function (bufferGeometry) {
if (bufferGeometry.drawMode === THREE.TrianglesDrawMode) {
bufferGeometry.computeVertexNormals();
return;
} else if (bufferGeometry.drawMode === THREE.TriangleStripDrawMode) {
if (bufferGeometry.attributes.position === undefined) {
return;
}
const inPositions = bufferGeometry.attributes.position.array;
if (bufferGeometry.attributes.normal === undefined) {
bufferGeometry.addAttribute(
'normal',
new THREE.BufferAttribute(new Float32Array(inPositions.length),
3));
} else {
// Reset existing normals to zero.
const array = bufferGeometry.attributes.normal.array;
for (let i = 0; i < array.length; ++i) {
array[ i ] = 0;
}
}
let outNormals = bufferGeometry.attributes.normal.array;
let pos0 = new THREE.Vector3();
let pos1 = new THREE.Vector3();
let pos2 = new THREE.Vector3();
let posDif0 = new THREE.Vector3(), posDif1 = new THREE.Vector3();
let localNormal = new THREE.Vector3();
const stripIndices = bufferGeometry.index.array;
for (let i = 2; i < stripIndices.length; ++i) {
let index0 = stripIndices[i - 2] * 3;
let index1 = stripIndices[i - 1] * 3;
let index2 = stripIndices[i] * 3;
// Skip degenerate triangles.
if (index0 === index1 || index0 === index2 || index1 === index2) {
continue;
}
if ((i & 1) !== 0) {
// Swap index 1 and 0 on odd indexed triangles.
const tmpIndex = index1;
index1 = index2;
index2 = tmpIndex;
}
// Get position values.
pos0.fromArray(inPositions, index0);
pos1.fromArray(inPositions, index1);
pos2.fromArray(inPositions, index2);
// Position differences
posDif0.subVectors(pos2, pos0);
posDif1.subVectors(pos1, pos0);
// Weighted normal.
localNormal.crossVectors(posDif1, posDif0);
// Update normals on vertices
outNormals[index0] += localNormal.x;
outNormals[index0 + 1] += localNormal.y;
outNormals[index0 + 2] += localNormal.z;
outNormals[index1] += localNormal.x;
outNormals[index1 + 1] += localNormal.y;
outNormals[index1 + 2] += localNormal.z;
outNormals[index2] += localNormal.x;
outNormals[index2 + 1] += localNormal.y;
outNormals[index2 + 2] += localNormal.z;
}
bufferGeometry.normalizeNormals();
bufferGeometry.attributes.normal.needsUpdate = true;
}
},
};
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