如何合并几何体并保持每个几何体的颜色在R3F中。

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英文:

How to merge geometries and keep one color per geometry in R3F

问题

将多个几何形状合并并保留每个几何形状的颜色。
3个合并多边形的示例如下。

如何合并几何体并保持每个几何体的颜色在R3F中。

英文:

The idea would be to merge several geometries and keep the color for each geometry.
An example with 3 merges polygones would be the following.

如何合并几何体并保持每个几何体的颜色在R3F中。

答案1

得分: 1

Here's the translated content:

可能的解决方案

  • 在合并它们之前为每个几何体设置color属性。
  • 使用合并后的几何体作为参数来创建mesh。作为子元素提供一个材质并激活vertexColors属性。

示例

假设我们想要合并3个多边形，每个多边形有一种颜色：

  1. // 要显示的多边形
  2. const zones = [{
  3.   name: 'zone1',
  4.   coords: [[-2,0],[-2,2],[-0.4,1], [-0.8,-1.5]],
  5.   color: 0xff0000
  6. },
  7. {
  8.   name: 'zone2',
  9.   coords: [[-6,0],[-6,2],[-6.4,1], [-6.8,-1.5]],
  10.   color: 0x0000ff
  11. },
  12. {
  13.   name: 'zone3',
  14.   coords: [[4,0],[4,2],[5.6,1], [6.8,-1.5]],
  15.   color: 0x0000ff
  16. }]
  • 使用属性创建合并后的几何体如下所示：
  1. let geometries = [];
  2. zones.forEach((zone, iZone) => {
  3.   const shape = new THREE.Shape();
  4.   const coords = zone.coords;
  5.   const color = new THREE.Color(zone.color);
  6.   const startPoint = coords[0];
  7.   // 画出形状
  8.   shape.moveTo(startPoint[0], startPoint[1]);
  9.   for (let i = 1; i < coords.length; i++) {
  10.     shape.lineTo(coords[i][0], coords[i][1]);
  11.   }
  12.   // 根据形状创建几何体
  13.   const geom = new THREE.ShapeGeometry(shape);
  14.   // 创建一个与索引长度相同的属性，用于存储颜色状态
  15.   const indicesLength = geom.attributes.position.count;
  16.   const aColor = new Float32Array(indicesLength * 3);
  17.   for (let k = 0; k < aColor.length; k += 3) {
  18.     aColor[k] = color.r;
  19.     aColor[k + 1] = color.g;
  20.     aColor[k + 2] = color.b;
  21.   }
  22.   geom.setAttribute('color', new THREE.BufferAttribute(aColor, 3));
  23.   geometries.push(geom);
  24. })
  25. const newMerged = BufferGeometryUtils.mergeGeometries(geometries)
  • 在你的jsx中，你会有以下内容：
  1. <mesh geometry={merged}>
  2.   {/* 激活顶点颜色 */}
  3.   <meshBasicMaterial vertexColors />
  4. </mesh>

可以在这里找到实现的示例：Codesandbox

英文:

Possible solution

  • Set the color attribute for each geometry before merging them.
  • Use mesh with the merged geometry as a parameter. Give a material as a child and activate the vertexColors properties.

EXAMPLE

Let's say we want to merge 3 polygons with one color per polygone:

  1. // Polygones to display
  2. const zones = [{
  3.   name:&#39;zone1&#39;,
  4.   coords:[[-2,0],[-2,2],[-0.4,1], [-0.8,-1.5]],
  5.   color: 0xff0000
  6. },
  7. {
  8.   name:&#39;zone2&#39;,
  9.   coords:[[-6,0],[-6,2],[-6.4,1], [-6.8,-1.5]],
  10.   color: 0x0000ff
  11. },
  12. {
  13.   name:&#39;zone3&#39;,
  14.   coords:[[4,0],[4,2],[5.6,1], [6.8,-1.5]],
  15.   color: 0x0000ff
  16. },
  17. ]
  • Creating the merged geometry with the attributes would look like this:
  1. let geometries = [];
  2. zones.forEach((zone,iZone) =&gt; {
  3.   const shape = new THREE.Shape();
  4.   const coords = zone.coords;
  5.   const color = new THREE.Color(zone.color);
  6.   const startPoint = coords[0];
  7.   // Draw the shape
  8.   shape.moveTo(startPoint[0],startPoint[1]);
  9.   for (let i=1;i&lt;coords.length; i++){
  10.     shape.lineTo(coords[i][0], coords[i][1]);
  11.   }
  12.   // Create the geometry thanks to the shape
  13.   const geom = new THREE.ShapeGeometry(shape);
  14.   // Create an attributes (same length that the indices) that will store the color state
  15.   const indicesLength = geom.attributes.position.count;
  16.   const aColor = new Float32Array(indicesLength * 3);
  17.   for (let k = 0; k &lt; aColor.length; k+=3){
  18.     aColor[k] = color.r;
  19.     aColor[k+1] = color.g;
  20.     aColor[k+2] = color.b;
  21.   }
  22.   geom.setAttribute(&#39;color&#39;, new THREE.BufferAttribute(aColor, 3));
  23.   geometries.push(geom);
  24. })
  25. const newMerged = BufferGeometryUtils.mergeGeometries(geometries)
  • And in your jsx you would have the following:
  1. &lt;mesh geometry={merged}&gt;
  2.   {/* activate vertex color */}
  3.   &lt;meshBasicMaterial vertexColors/&gt;
  4. &lt;/mesh&gt;

An example of the implementation can be found here: Codesandbox

huangapple
  • 本文由 发表于 2023年5月31日 23:12:01
  • 转载请务必保留本文链接：https://go.coder-hub.com/76374983.html
  • react-three-fiber
  • three.js
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