Threejs - 环在旋转之前不会出现？
Threejs - Ring doesn't appear until rotated?
在 Three.js 中，我正在尝试制作一个交互式点击并拖动以旋转的对象，该对象由一个环和一条线组成。我 运行 遇到了一个奇怪的问题，在第一次旋转之前，圆环不会出现。我的代码如下。
为什么直到对象旋转才出现圆环？
编辑：我发现 this.ring.rotateX(Math.PI / 2) 似乎是阻止环出现的原因。
初始化（环不可见）
经过微小的旋转（环可见）
<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<script src='https://cdnjs.cloudflare.com/ajax/libs/three.js/r128/three.min.js'></script>
<!-- TheJim01: Adding CDN jquery for snippet -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<!-- <script src="js/jquery.min.js"></script> -->
<!-- <script src="{{ url_for('static', filename='js/jquery.min.js') }}"></script>-->
</head>
<body>
<canvas id="threejs_covering_canvas" width="1000" height="500"></canvas>
<script>
const canvas = $('#threejs_covering_canvas')[0];
const scene = new THREE.Scene();
const camera = new THREE.OrthographicCamera(-10, 10, 5, -5, 1, 1000);
camera.position.z = 5;
const renderer = new THREE.WebGLRenderer({
canvas
});
document.body.appendChild(renderer.domElement);
function vecToSurfaceNormalRGB(vec) {
// normals are in range [-1, 1], so this maps to [0, 1]
let red = 0.5 * vec.x + 0.5;
let green = 0.5 * vec.y + 0.5;
let blue = 0.5 * vec.z + 0.5;
return new THREE.Color(red, green, blue);
}
class KoenderinkCircle extends THREE.Object3D {
constructor(dir, origin) {
super();
this.type = 'KoenderinkCircle';
this._axis = new THREE.Vector3();
this._lineGeometry = new THREE.BufferGeometry();
this._lineGeometry.setAttribute('position', new THREE.Float32BufferAttribute([0, 0, 0, 0, 1, 0], 3));
this.line = new THREE.Line(this._lineGeometry, new THREE.LineBasicMaterial({
color: 0xffff00,
toneMapped: false,
linewidth: 4
}));
this.add(this.line)
// THREE.RingBufferGeometry
this._ringGeometry = new THREE.RingBufferGeometry(0.5, 1, 100);
this.ring = new THREE.Mesh(this._ringGeometry, new THREE.MeshNormalMaterial({
side: THREE.DoubleSide
}));
// Rotate the ring such that line is normal to plane the ring lies on.
this.ring.rotateX(Math.PI / 2);
this.add(this.ring);
this.position.copy(origin);
this.updateLineColor();
this.setDirection(dir)
}
setDirection(dir) {
// dir is assumed to be normalized
if (dir.y > 0.99999) {
this.quaternion.set(0, 0, 0, 1);
} else if (dir.y < -0.99999) {
this.quaternion.set(1, 0, 0, 0);
} else {
this._axis.set(dir.z, 0, -dir.x).normalize();
const radians = Math.acos(dir.y);
this.quaternion.setFromAxisAngle(this._axis, radians);
}
}
updateLineColor() {
let lineDirection = new THREE.Vector3();
this.ring.getWorldDirection(lineDirection);
// For some reason, ring points in opposite direction.
// Multiply by -1 to get correct direction.
lineDirection.multiplyScalar(-1.)
// TODO: Why does color work correctly only on the front half, not the back half?
this.line.material.color.set(vecToSurfaceNormalRGB(lineDirection.normalize()));
}
}
// var koenderinkIndicatorDirection = new THREE.Vector3(1, 1, 0).normalize();
var koenderinkIndicatorDirection = new THREE.Vector3(0, 1, 0).normalize();
var koenderinkIndicatorPosition = new THREE.Vector3(-4, 2, 0);
const koenderinkIndicator = new KoenderinkCircle(
koenderinkIndicatorDirection,
koenderinkIndicatorPosition)
scene.add(koenderinkIndicator);
var pointer = new THREE.Vector3();
var mouseStartOrthographicPosition = new THREE.Vector3();
var mousePenultimateOrthographicPosition = new THREE.Vector3();
var mouseCurrentOrthographicPosition = new THREE.Vector3();
var distanceCurrentMinusPenultimate = new THREE.Vector3();
var distancePenultimateMinusStart = new THREE.Vector3();
var distanceCurrentMinusStart = new THREE.Vector3();
var angle;
var axis = new THREE.Vector3();
let lineWorldDirection = new THREE.Vector3();
let koenderinkIndicatorWorldDirection = new THREE.Vector3();
// This vector will be used to check that rotation doesn't permit pointing
// line in negative Z direction.
let negativeZVector = new THREE.Vector3(0, 0, -1);
const radius = 1;
const radiusSquared = radius * radius;
let rotationQuaternion = new THREE.Quaternion();
let mouseDown = false;
function setMouseCurrentOrthographicPosition(event) {
let canvasBoundingBox = canvas.getBoundingClientRect();
let sketchpadCurrentHeight = canvasBoundingBox.bottom - canvasBoundingBox.top;
let sketchpadCurrentWidth = canvasBoundingBox.right - canvasBoundingBox.left;
// Compute mouse location relative to canvasBoundingBox, then normalize to [-1, 1]
// I think this is correct
pointer.x = ((event.clientX - canvasBoundingBox.left) / sketchpadCurrentWidth) * 2 - 1;
pointer.y = -((event.clientY - canvasBoundingBox.top) / sketchpadCurrentHeight) * 2 + 1;
// First computes location of mouse on z=0 plane
// See:
// Third argument is irrelevant.
mouseCurrentOrthographicPosition.set(pointer.x, pointer.y, 0);
// Projects from ThreeJS-independent "normalized device coordinate space" (i.e. -1 to 1)
// to "world space" i.e. the coordinates used by ThreeJS
mouseCurrentOrthographicPosition.unproject(camera);
return mouseCurrentOrthographicPosition
}
canvas.addEventListener('mousedown', function(event) {
// Save mouseStartOrthographicPosition.
mouseStartOrthographicPosition.copy(setMouseCurrentOrthographicPosition(event));
// Initialize the 2nd most recent othographic position.
mousePenultimateOrthographicPosition.copy(mouseStartOrthographicPosition);
mouseDown = true;
// console.log('mousedown set to True');
});
canvas.addEventListener('mouseup', function(event) {
mouseDown = false;
});
function rotateIndicator(event) {
if (mouseDown) {
setMouseCurrentOrthographicPosition(event);
distanceCurrentMinusPenultimate.subVectors(mouseCurrentOrthographicPosition, mousePenultimateOrthographicPosition);
distanceCurrentMinusStart.subVectors(mouseCurrentOrthographicPosition, mouseStartOrthographicPosition);
distancePenultimateMinusStart.subVectors(mousePenultimateOrthographicPosition, mouseStartOrthographicPosition);
let cond1 = Math.pow(distancePenultimateMinusStart.x, 2) + Math.pow(distancePenultimateMinusStart.y, 2) + 0.0001 < radiusSquared;
let cond2 = Math.pow(distanceCurrentMinusStart.x, 2) + Math.pow(distanceCurrentMinusStart.y, 2) + 0.0001 < radiusSquared;
if (cond1 && cond2) {
let v0 = new THREE.Vector3(
distancePenultimateMinusStart.x,
distancePenultimateMinusStart.y,
Math.sqrt(radiusSquared - Math.pow(distancePenultimateMinusStart.x, 2) - Math.pow(distancePenultimateMinusStart.y, 2))
).normalize()
let v1 = new THREE.Vector3(
distanceCurrentMinusStart.x,
distanceCurrentMinusStart.y,
Math.sqrt(radiusSquared - Math.pow(distanceCurrentMinusStart.x, 2) - Math.pow(distanceCurrentMinusStart.y, 2))
).normalize()
angle = Math.acos(Math.max(Math.min(v0.dot(v1), 0.999), -0.999));
axis.crossVectors(v0, v1).normalize()
rotationQuaternion.setFromAxisAngle(axis, angle);
// For some reason, the line world direction is rotated 90 degrees towards the camera.
// i.e. if the line is pointing vertically up, the world direction is (0, 0, 1)
// if the line is pointing towards the camera, the world direction is (0, -1, 0)
console.log('koenderinkIndicator axis: ', koenderinkIndicator._axis)
koenderinkIndicator.getWorldDirection(koenderinkIndicatorWorldDirection);
console.log('lineWorldDirection Before Quaternion: ', koenderinkIndicatorWorldDirection)
// Apply rotation to lineWorldDirection
lineWorldDirection.applyQuaternion(rotationQuaternion)
// console.log('lineWorldDirection After Quaternion: ', lineWorldDirection)
// Check whether rotation would result in line facing backwards.
let dotWithZDirection = lineWorldDirection.dot(negativeZVector)
// console.log('Dot with Z Direction: ', dotWithZDirection)
koenderinkIndicator.applyQuaternion(rotationQuaternion);
koenderinkIndicator.updateLineColor();
}
mousePenultimateOrthographicPosition.copy(mouseCurrentOrthographicPosition);
}
}
canvas.addEventListener('mousemove', rotateIndicator);
function animate() {
requestAnimationFrame(animate);
renderer.render(scene, camera);
}
animate();
</script>
</body>
</html>
平面物体本质上没有体积。它们实际上是二维的。因此，您的初始视图是“在边缘”看圆环，这意味着您正在沿着没有维度值的平面看，因此该对象看起来是不可见的。 “稍微”移动视图足以使您的视点不再与环在同一平面上，因此环出现。
如果您希望能够从各个角度看到圆环，请考虑给它一些深度，比如一个非常短的圆柱体（高度仍大于零），上面有一个孔。
在 Three.js 中，我正在尝试制作一个交互式点击并拖动以旋转的对象，该对象由一个环和一条线组成。我 运行 遇到了一个奇怪的问题，在第一次旋转之前，圆环不会出现。我的代码如下。
为什么直到对象旋转才出现圆环？
编辑：我发现 this.ring.rotateX(Math.PI / 2) 似乎是阻止环出现的原因。
初始化（环不可见）
经过微小的旋转（环可见）
<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<script src='https://cdnjs.cloudflare.com/ajax/libs/three.js/r128/three.min.js'></script>
<!-- TheJim01: Adding CDN jquery for snippet -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<!-- <script src="js/jquery.min.js"></script> -->
<!-- <script src="{{ url_for('static', filename='js/jquery.min.js') }}"></script>-->
</head>
<body>
<canvas id="threejs_covering_canvas" width="1000" height="500"></canvas>
<script>
const canvas = $('#threejs_covering_canvas')[0];
const scene = new THREE.Scene();
const camera = new THREE.OrthographicCamera(-10, 10, 5, -5, 1, 1000);
camera.position.z = 5;
const renderer = new THREE.WebGLRenderer({
canvas
});
document.body.appendChild(renderer.domElement);
function vecToSurfaceNormalRGB(vec) {
// normals are in range [-1, 1], so this maps to [0, 1]
let red = 0.5 * vec.x + 0.5;
let green = 0.5 * vec.y + 0.5;
let blue = 0.5 * vec.z + 0.5;
return new THREE.Color(red, green, blue);
}
class KoenderinkCircle extends THREE.Object3D {
constructor(dir, origin) {
super();
this.type = 'KoenderinkCircle';
this._axis = new THREE.Vector3();
this._lineGeometry = new THREE.BufferGeometry();
this._lineGeometry.setAttribute('position', new THREE.Float32BufferAttribute([0, 0, 0, 0, 1, 0], 3));
this.line = new THREE.Line(this._lineGeometry, new THREE.LineBasicMaterial({
color: 0xffff00,
toneMapped: false,
linewidth: 4
}));
this.add(this.line)
// THREE.RingBufferGeometry
this._ringGeometry = new THREE.RingBufferGeometry(0.5, 1, 100);
this.ring = new THREE.Mesh(this._ringGeometry, new THREE.MeshNormalMaterial({
side: THREE.DoubleSide
}));
// Rotate the ring such that line is normal to plane the ring lies on.
this.ring.rotateX(Math.PI / 2);
this.add(this.ring);
this.position.copy(origin);
this.updateLineColor();
this.setDirection(dir)
}
setDirection(dir) {
// dir is assumed to be normalized
if (dir.y > 0.99999) {
this.quaternion.set(0, 0, 0, 1);
} else if (dir.y < -0.99999) {
this.quaternion.set(1, 0, 0, 0);
} else {
this._axis.set(dir.z, 0, -dir.x).normalize();
const radians = Math.acos(dir.y);
this.quaternion.setFromAxisAngle(this._axis, radians);
}
}
updateLineColor() {
let lineDirection = new THREE.Vector3();
this.ring.getWorldDirection(lineDirection);
// For some reason, ring points in opposite direction.
// Multiply by -1 to get correct direction.
lineDirection.multiplyScalar(-1.)
// TODO: Why does color work correctly only on the front half, not the back half?
this.line.material.color.set(vecToSurfaceNormalRGB(lineDirection.normalize()));
}
}
// var koenderinkIndicatorDirection = new THREE.Vector3(1, 1, 0).normalize();
var koenderinkIndicatorDirection = new THREE.Vector3(0, 1, 0).normalize();
var koenderinkIndicatorPosition = new THREE.Vector3(-4, 2, 0);
const koenderinkIndicator = new KoenderinkCircle(
koenderinkIndicatorDirection,
koenderinkIndicatorPosition)
scene.add(koenderinkIndicator);
var pointer = new THREE.Vector3();
var mouseStartOrthographicPosition = new THREE.Vector3();
var mousePenultimateOrthographicPosition = new THREE.Vector3();
var mouseCurrentOrthographicPosition = new THREE.Vector3();
var distanceCurrentMinusPenultimate = new THREE.Vector3();
var distancePenultimateMinusStart = new THREE.Vector3();
var distanceCurrentMinusStart = new THREE.Vector3();
var angle;
var axis = new THREE.Vector3();
let lineWorldDirection = new THREE.Vector3();
let koenderinkIndicatorWorldDirection = new THREE.Vector3();
// This vector will be used to check that rotation doesn't permit pointing
// line in negative Z direction.
let negativeZVector = new THREE.Vector3(0, 0, -1);
const radius = 1;
const radiusSquared = radius * radius;
let rotationQuaternion = new THREE.Quaternion();
let mouseDown = false;
function setMouseCurrentOrthographicPosition(event) {
let canvasBoundingBox = canvas.getBoundingClientRect();
let sketchpadCurrentHeight = canvasBoundingBox.bottom - canvasBoundingBox.top;
let sketchpadCurrentWidth = canvasBoundingBox.right - canvasBoundingBox.left;
// Compute mouse location relative to canvasBoundingBox, then normalize to [-1, 1]
// I think this is correct
pointer.x = ((event.clientX - canvasBoundingBox.left) / sketchpadCurrentWidth) * 2 - 1;
pointer.y = -((event.clientY - canvasBoundingBox.top) / sketchpadCurrentHeight) * 2 + 1;
// First computes location of mouse on z=0 plane
// See:
// Third argument is irrelevant.
mouseCurrentOrthographicPosition.set(pointer.x, pointer.y, 0);
// Projects from ThreeJS-independent "normalized device coordinate space" (i.e. -1 to 1)
// to "world space" i.e. the coordinates used by ThreeJS
mouseCurrentOrthographicPosition.unproject(camera);
return mouseCurrentOrthographicPosition
}
canvas.addEventListener('mousedown', function(event) {
// Save mouseStartOrthographicPosition.
mouseStartOrthographicPosition.copy(setMouseCurrentOrthographicPosition(event));
// Initialize the 2nd most recent othographic position.
mousePenultimateOrthographicPosition.copy(mouseStartOrthographicPosition);
mouseDown = true;
// console.log('mousedown set to True');
});
canvas.addEventListener('mouseup', function(event) {
mouseDown = false;
});
function rotateIndicator(event) {
if (mouseDown) {
setMouseCurrentOrthographicPosition(event);
distanceCurrentMinusPenultimate.subVectors(mouseCurrentOrthographicPosition, mousePenultimateOrthographicPosition);
distanceCurrentMinusStart.subVectors(mouseCurrentOrthographicPosition, mouseStartOrthographicPosition);
distancePenultimateMinusStart.subVectors(mousePenultimateOrthographicPosition, mouseStartOrthographicPosition);
let cond1 = Math.pow(distancePenultimateMinusStart.x, 2) + Math.pow(distancePenultimateMinusStart.y, 2) + 0.0001 < radiusSquared;
let cond2 = Math.pow(distanceCurrentMinusStart.x, 2) + Math.pow(distanceCurrentMinusStart.y, 2) + 0.0001 < radiusSquared;
if (cond1 && cond2) {
let v0 = new THREE.Vector3(
distancePenultimateMinusStart.x,
distancePenultimateMinusStart.y,
Math.sqrt(radiusSquared - Math.pow(distancePenultimateMinusStart.x, 2) - Math.pow(distancePenultimateMinusStart.y, 2))
).normalize()
let v1 = new THREE.Vector3(
distanceCurrentMinusStart.x,
distanceCurrentMinusStart.y,
Math.sqrt(radiusSquared - Math.pow(distanceCurrentMinusStart.x, 2) - Math.pow(distanceCurrentMinusStart.y, 2))
).normalize()
angle = Math.acos(Math.max(Math.min(v0.dot(v1), 0.999), -0.999));
axis.crossVectors(v0, v1).normalize()
rotationQuaternion.setFromAxisAngle(axis, angle);
// For some reason, the line world direction is rotated 90 degrees towards the camera.
// i.e. if the line is pointing vertically up, the world direction is (0, 0, 1)
// if the line is pointing towards the camera, the world direction is (0, -1, 0)
console.log('koenderinkIndicator axis: ', koenderinkIndicator._axis)
koenderinkIndicator.getWorldDirection(koenderinkIndicatorWorldDirection);
console.log('lineWorldDirection Before Quaternion: ', koenderinkIndicatorWorldDirection)
// Apply rotation to lineWorldDirection
lineWorldDirection.applyQuaternion(rotationQuaternion)
// console.log('lineWorldDirection After Quaternion: ', lineWorldDirection)
// Check whether rotation would result in line facing backwards.
let dotWithZDirection = lineWorldDirection.dot(negativeZVector)
// console.log('Dot with Z Direction: ', dotWithZDirection)
koenderinkIndicator.applyQuaternion(rotationQuaternion);
koenderinkIndicator.updateLineColor();
}
mousePenultimateOrthographicPosition.copy(mouseCurrentOrthographicPosition);
}
}
canvas.addEventListener('mousemove', rotateIndicator);
function animate() {
requestAnimationFrame(animate);
renderer.render(scene, camera);
}
animate();
</script>
</body>
</html>
平面物体本质上没有体积。它们实际上是二维的。因此，您的初始视图是“在边缘”看圆环，这意味着您正在沿着没有维度值的平面看，因此该对象看起来是不可见的。 “稍微”移动视图足以使您的视点不再与环在同一平面上，因此环出现。
如果您希望能够从各个角度看到圆环，请考虑给它一些深度，比如一个非常短的圆柱体（高度仍大于零），上面有一个孔。