我正在尝试使用我根据本文https://threejsfundamentals.org/threejs/lessons/threejs-picking.html后半段修改的代码，通过Points实现GPU选择。
对于我来说，它在台式机上运行良好，但是我开始测试不同的浏览器和设备，但无法正常运行。我做了一个Codepen来说明https://codepen.io/deklanw/pen/OJVVmEd?editors=1111
body {
margin: 0;
}
#c {
width: 100vw;
height: 100vh;
display: block;
}<canvas id="c"></canvas>
<script type="module">
// Three.js - Picking - RayCaster w/Transparency
// from https://threejsfundamentals.org/threejs/threejs-picking-gpu.html
import * as THREE from "https://threejsfundamentals.org/threejs/resources/threejs/r113/build/three.module.js";
function main() {
const canvas = document.querySelector("#c");
const renderer = new THREE.WebGLRenderer({ canvas });
const fov = 60;
const aspect = 2; // the canvas default
const near = 0.1;
const far = 200;
const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
camera.position.z = 30;
const scene = new THREE.Scene();
scene.background = new THREE.Color(0);
const pickingScene = new THREE.Scene();
pickingScene.background = new THREE.Color(0);
// put the camera on a pole (parent it to an object)
// so we can spin the pole to move the camera around the scene
const cameraPole = new THREE.Object3D();
scene.add(cameraPole);
cameraPole.add(camera);
function randomNormalizedColor() {
return Math.random();
}
function getRandomInt(n) {
return Math.floor(Math.random() * n);
}
function getCanvasRelativePosition(e) {
const rect = canvas.getBoundingClientRect();
return {
x: e.clientX - rect.left,
y: e.clientY - rect.top
};
}
const textureLoader = new THREE.TextureLoader();
const particleTexture =
"https://raw.githubusercontent.com/mrdoob/three.js/master/examples/textures/sprites/ball.png";
const vertexShader = `
attribute float size;
attribute vec3 customColor;
varying vec3 vColor;
void main() {
vColor = customColor;
vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );
gl_PointSize = size * ( 100.0 / length( mvPosition.xyz ) );
gl_Position = projectionMatrix * mvPosition;
}
`;
const fragmentShader = `
uniform sampler2D texture;
varying vec3 vColor;
void main() {
vec4 tColor = texture2D( texture, gl_PointCoord );
if (tColor.a < 0.5) discard;
gl_FragColor = mix( vec4( vColor.rgb, 1.0 ), tColor, 0.1 );
}
`;
const pickFragmentShader = `
uniform sampler2D texture;
varying vec3 vColor;
void main() {
vec4 tColor = texture2D( texture, gl_PointCoord );
if (tColor.a < 0.25) discard;
gl_FragColor = vec4( vColor.rgb, 1.0);
}
`;
const materialSettings = {
uniforms: {
texture: {
type: "t",
value: textureLoader.load(particleTexture)
}
},
vertexShader: vertexShader,
fragmentShader: fragmentShader,
blending: THREE.NormalBlending,
depthTest: true,
transparent: false
};
const createParticleMaterial = () => {
const material = new THREE.ShaderMaterial(materialSettings);
return material;
};
const createPickingMaterial = () => {
const material = new THREE.ShaderMaterial({
...materialSettings,
fragmentShader: pickFragmentShader,
blending: THREE.NormalBlending
});
return material;
};
const geometry = new THREE.BufferGeometry();
const pickingGeometry = new THREE.BufferGeometry();
const colors = [];
const sizes = [];
const pickingColors = [];
const pickingColor = new THREE.Color();
const positions = [];
for (let i = 0; i < 30; i++) {
colors[3 * i] = randomNormalizedColor();
colors[3 * i + 1] = randomNormalizedColor();
colors[3 * i + 2] = randomNormalizedColor();
const rgbPickingColor = pickingColor.setHex(i + 1);
pickingColors[3 * i] = rgbPickingColor.r;
pickingColors[3 * i + 1] = rgbPickingColor.g;
pickingColors[3 * i + 2] = rgbPickingColor.b;
sizes[i] = getRandomInt(20);
positions[3 * i] = getRandomInt(20);
positions[3 * i + 1] = getRandomInt(20);
positions[3 * i + 2] = getRandomInt(20);
}
geometry.setAttribute(
"position",
new THREE.Float32BufferAttribute(positions, 3)
);
geometry.setAttribute(
"customColor",
new THREE.Float32BufferAttribute(colors, 3)
);
geometry.setAttribute("size", new THREE.Float32BufferAttribute(sizes, 1));
geometry.computeBoundingBox();
const material = createParticleMaterial();
const points = new THREE.Points(geometry, material);
// setup geometry and material for GPU picking
pickingGeometry.setAttribute(
"position",
new THREE.Float32BufferAttribute(positions, 3)
);
pickingGeometry.setAttribute(
"customColor",
new THREE.Float32BufferAttribute(pickingColors, 3)
);
pickingGeometry.setAttribute(
"size",
new THREE.Float32BufferAttribute(sizes, 1)
);
pickingGeometry.computeBoundingBox();
const pickingMaterial = createPickingMaterial();
const pickingPoints = new THREE.Points(pickingGeometry, pickingMaterial);
scene.add(points);
pickingScene.add(pickingPoints);
function resizeRendererToDisplaySize(renderer) {
const canvas = renderer.domElement;
const width = canvas.clientWidth;
const height = canvas.clientHeight;
const needResize = canvas.width !== width || canvas.height !== height;
if (needResize) {
renderer.setSize(width, height, false);
}
return needResize;
}
class GPUPickHelper {
constructor() {
// create a 1x1 pixel render target
this.pickingTexture = new THREE.WebGLRenderTarget(1, 1);
this.pixelBuffer = new Uint8Array(4);
}
pick(cssPosition, pickingScene, camera) {
const { pickingTexture, pixelBuffer } = this;
// set the view offset to represent just a single pixel under the mouse
const pixelRatio = renderer.getPixelRatio();
camera.setViewOffset(
renderer.getContext().drawingBufferWidth, // full width
renderer.getContext().drawingBufferHeight, // full top
(cssPosition.x * pixelRatio) | 0, // rect x
(cssPosition.y * pixelRatio) | 0, // rect y
1, // rect width
1 // rect height
);
// render the scene
renderer.setRenderTarget(pickingTexture);
renderer.render(pickingScene, camera);
renderer.setRenderTarget(null);
// clear the view offset so rendering returns to normal
camera.clearViewOffset();
//read the pixel
renderer.readRenderTargetPixels(
pickingTexture,
0, // x
0, // y
1, // width
1, // height
pixelBuffer
);
const id =
(pixelBuffer[0] << 16) | (pixelBuffer[1] << 8) | pixelBuffer[2];
console.log(`You clicked sphere number ${id}`);
return id;
}
}
const pickHelper = new GPUPickHelper();
function render(time) {
time *= 0.001; // convert to seconds;
if (resizeRendererToDisplaySize(renderer)) {
const canvas = renderer.domElement;
camera.aspect = canvas.clientWidth / canvas.clientHeight;
camera.updateProjectionMatrix();
}
cameraPole.rotation.y = time * 0.1;
renderer.render(scene, camera);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
function onClick(e) {
const pickPosition = getCanvasRelativePosition(e);
const pickedID = pickHelper.pick(pickPosition, pickingScene, camera);
}
function onTouch(e) {
const touch = e.touches[0];
const pickPosition = getCanvasRelativePosition(touch);
const pickedID = pickHelper.pick(pickPosition, pickingScene, camera);
}
window.addEventListener("mousedown", onClick);
window.addEventListener("touchstart", onTouch);
}
main();
</script>
如果在节点上单击（或点击），则其ID将在控制台中弹出。在某些设备上，我只能得到0，就像选择背景一样。
有人知道为什么吗？
此外，如果在这种情况下（通过ShaderMaterial通过可变大小的点进行点网格化）有一种方法可以进行拾取，但仍然可以轻松执行，我很好奇
编辑：
我删除了1x1渲染目标优化，似乎已经解决了。现在，我想知道该优化会导致什么问题。
答案 0 :(得分：1)
问题是您不能以这种方式在设备之间使用Points。
无论是在中心外还是不在设备外都绘制点（OpenGL ES / WebGL规范说仍然应该绘制，而OpenGL规范说不是）。没有针对它的测试，因此每个驱动程序都是不同），而要解决这些问题，WebGL解决方案将耗费过多的精力，因此它们无法解决。 AFAIK Intel和NVidia确实绘制了它们。基于AMD和PowerVR的（iPhone）不会绘制它们。
如果使圆圈变大并确保它们脱离屏幕（并且可能需要使画布变小），则可以看到此问题。在某些设备上，它们将平滑地移出屏幕，而在其他设备上，它们的中心一旦移出屏幕，它们就会消失（通常取决于点的大小和视口的大小）
这意味着您的示例在任何情况下都不会真正起作用，无论是否使用1x1像素渲染目标，仅是使用1x1像素渲染目标，几乎所有圆圈的中心都在1x1像素区域之外，因此它们不会不能在某些设备上绘制。当您使渲染目标与画布的大小匹配时，大多数圆的中心都在内部，但是边缘仍然会出现拾取错误。
要解决此问题，您将需要使用四边形而不是点来绘制点。有很多方法可以做到这一点。将每个四边形绘制为单独的网格或精灵，或者将所有四边形合并为另一个网格，或者使用InstancedMesh，在该点上每个点都需要一个矩阵，或者编写自定义着色器来做点（请参见{ {3}}）
请注意，要点也有其他问题。默认情况下，它们不会相对于画布大小缩放（当然，您可以在着色器中修复此问题，并且three.js也具有此选项）。它们还具有与设备无关的最大尺寸，根据规格，该尺寸可以低至1像素。它们对设备像素比率设置的响应不佳（尽管您也可以在代码中对其进行修复）。由于所有这些原因，积分的用途有限。代码绘制的大圆圈可以说超出了这个限制。