本文介绍了THREE.js - 旋转移动 3D 球的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我是 THREE.js 的新手，物理知识很差 - 但我正在尝试构建一个足球游戏引擎(从顶部看)，现在我正在努力控制球的运动.
I'm new to THREE.js and with a very poor knowledge in physics - but I am trying to build a football game engine (viewed from top) and right now I'm struggling with the movement of the ball.
当试图将球从一侧移动到另一侧时，旋转始终面向一个方向，我不明白如何使其沿其移动方向旋转.
when trying to move the ball from side to side, the rotation is always facing one direction and I dont understand how to make this rotate in the direction its moving at.
我添加了一个简单的代码来显示这个问题.非常感谢您的帮助.
Ive added a simple code showing this issue. your help is much appreciated.
/*
*
* SET UP MOTION PARAMS
*
*/
var degrees = 10;
var power = 1;
var angleRad = degrees * Math.PI / 120;
var velocityX = Math.cos(angleRad) * power;
var velocityY = Math.sin(angleRad) * power;
var velocityZ = 1;
var friction = 1;
var gravity = 0.2;
var bounciness = 0.9;
window.onload = function (params) {
/*
*
* SET UP THE WORLD
*
*/
//set up the ratio
var gWidth = window.innerWidth;
var gHeight = window.innerHeight;
var ratio = gWidth / gHeight;
var borders = [40, 24] //indicate where the ball needs to move in mirror position
//set the scene
scene = new THREE.Scene();
scene.background = new THREE.Color(0xeaeaea);
//set the camera
var camera = new THREE.PerspectiveCamera(35, ratio, 0.1, 1000);
camera.position.z = 120;
//set the light
var light = new THREE.SpotLight(0xffffff, 1);
light.position.set(100, 1, 0);
light.castShadow = true;
light.position.set(0, 0, 100);
scene.add(light);
// set the renderer
var renderer = new THREE.WebGLRenderer();
//properties for casting shadow
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;
renderer.setSize(gWidth, gHeight);
document.body.appendChild(renderer.domElement);
/*
*
* ADD MESH TO SCENE
*
*/
// create and add the ball
var geometry = new THREE.SphereGeometry(5, 5, 5);
var material = new THREE.MeshLambertMaterial({ color: 'gray' });
var ball = new THREE.Mesh(geometry, material);
ball.castShadow = true;
ball.receiveShadow = false;
scene.add(ball);
// create and add the field
var margin = 20;
var fieldRatio = 105 / 68;
var width = 90;
var height = width / fieldRatio;
var material = new THREE.MeshLambertMaterial({ color: 'green' });
var geometry = new THREE.BoxGeometry(width, height, 1);
var field = new THREE.Mesh(geometry, material);
field.receiveShadow = true;
field.position.z = -1;
scene.add(field);
/*
* setting up rotation axis
*/
var rotation_matrix = null;
var setQuaternions = function () {
setMatrix();
ball.rotation.set(Math.PI / 2, Math.PI / 4, Math.PI / 4); // Set initial rotation
ball.matrix.makeRotationFromEuler(ball.rotation); // Apply rotation to the object's matrix
}
var setMatrix = function () {
rotation_matrix = new THREE.Matrix4().makeRotationZ(angleRad); // Animated rotation will be in .01 radians along object's X axis
}
setQuaternions();
/*
*
* ANIMATION STEP
*
*/
var render = function (params) {
// add velocity to ball
ball.position.x += velocityX;
ball.position.z += velocityZ;
ball.position.y += velocityY;
//validate if ball is stop moving
if (Math.abs(velocityX) < 0.02 && Math.abs(velocityY) < 0.02) {
console.log("DONE!");
return;
}
// handle boucing effect
if (ball.position.z < 1) {
velocityZ *= -bounciness;
ball.position.z = 1
}
// Update the object's rotation & apply it
ball.matrix.multiply(rotation_matrix);
ball.rotation.setFromRotationMatrix(ball.matrix);
//reducing speed by friction
angleRad *= friction;
velocityX *= friction;
velocityY *= friction;
velocityZ *= friction;
//set up the matrix
setMatrix();
//validate ball is withing its borders otherwise go in the mirror direction
if (Math.abs(ball.position.x) > borders[0]) {
velocityX *= -1;
ball.position.x = (ball.position.x < 0) ? borders[0] * -1 : borders[0];
}
if (Math.abs(ball.position.y) > borders[1]) {
velocityY *= -1;
ball.position.y = (ball.position.y < 0) ? borders[1] * -1 : borders[1];
}
// reduce ball height with gravity
velocityZ -= gravity;
//render the page
renderer.render(scene, camera);
requestAnimationFrame(render);
}
render();
}body {
padding: 0;
margin: 0;
}<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/96/three.min.js"></script>
<html>
<head>
</head>
<body>
</body>
</html>推荐答案
如果你想包括摩擦和惯性等，这实际上是一个非常高级的物理方法，可以用超现实的方式来做.但是你可以走一些捷径获得不错的视觉滚动效果...
This is actually a pretty advanced bit of physics to do in a super realistic way if you want to include friction and inertia, etc. But you can take some shortcuts to get a decent visual rolling effect...
如果你在球的运动方向上取向量，你可以得到一个垂直的向量.
If you take the vector in the movement direction of the ball, you can get a perpendicular vector.. by taking the .cross product of the movement vector, with the world up vector.
该向量是球与地面完全摩擦时将围绕其旋转的轴.一旦你有了那个轴，你就可以对对象使用 .rotateOnWorldAxis(轴:Vector3，角度:浮点).
That vector is the axis that a ball would rotate around if it had complete friction with the ground. Once you have that axis, you can use .rotateOnWorldAxis ( axis : Vector3, angle : Float ) with the object..
然后你必须根据球的半径和行进的距离计算出旋转多少..所以它是运动向量*(PI*2)的长度(在我的代码中称为幅度)/球的周长.
then you have to figure out how much to rotate, based on the radius of the ball, and the distance travelled.. so it's the length (called magnitude in my code below) of the movement vector * (PI*2) / the circumference of the ball.
让我知道这是否有帮助...
Let me know if this helps...
ps - 您的angleRad"计算结果是除以 120 而不是 180 .. 我修正了这个问题.
p.s - Your "angleRad" computation was dividing by 120 instead of 180.. i fixed that.
/*
*
* SET UP MOTION PARAMS
*
*/
var degrees = 35;
var power = 0.45;
var angleRad = degrees * Math.PI / 180;
var velocityX = Math.cos(angleRad) * power;
var velocityY = Math.sin(angleRad) * power;
var velocityZ = 1;
var friction = 1;
var gravity = 0.2;
var bounciness = 0.9;
var ballRadius = 5;
var ballCircumference = Math.PI * ballRadius * 2;
var ballVelocity = new THREE.Vector3();
var ballRotationAxis = new THREE.Vector3(0, 1, 0);
window.onload = function(params) {
/*
*
* SET UP THE WORLD
*
*/
//set up the ratio
var gWidth = window.innerWidth;
var gHeight = window.innerHeight;
var ratio = gWidth / gHeight;
var borders = [40, 24] //indicate where the ball needs to move in mirror position
//set the scene
scene = new THREE.Scene();
scene.background = new THREE.Color(0xeaeaea);
//set the camera
var camera = new THREE.PerspectiveCamera(35, ratio, 0.1, 1000);
camera.position.z = 120;
//set the light
var light = new THREE.SpotLight(0xffffff, 1);
light.position.set(100, 1, 0);
light.castShadow = true;
light.position.set(0, 0, 35);
scene.add(light);
// set the renderer
var renderer = new THREE.WebGLRenderer();
//properties for casting shadow
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;
renderer.setSize(gWidth, gHeight);
document.body.appendChild(renderer.domElement);
/*
*
* ADD MESH TO SCENE
*
*/
// create and add the ball
var geometry = new THREE.SphereGeometry(ballRadius, 8, 8);
//make a checkerboard texture for the ball...
var canv = document.createElement('canvas')
canv.width = canv.height = 256;
var ctx = canv.getContext('2d')
ctx.fillStyle = 'white';
ctx.fillRect(0, 0, 256, 256);
ctx.fillStyle = 'black';
for (var y = 0; y < 16; y++)
for (var x = 0; x < 16; x++)
if ((x & 1) != (y & 1)) ctx.fillRect(x * 16, y * 16, 16, 16);
var ballTex = new THREE.Texture(canv);
ballTex.needsUpdate = true;
var material = new THREE.MeshLambertMaterial({
map: ballTex
});
var ball = new THREE.Mesh(geometry, material);
ball.castShadow = true;
ball.receiveShadow = false;
scene.add(ball);
// create and add the field
var margin = 20;
var fieldRatio = 105 / 68;
var width = 90;
var height = width / fieldRatio;
var material = new THREE.MeshLambertMaterial({
color: 'green'
});
var geometry = new THREE.BoxGeometry(width, height, 1);
var field = new THREE.Mesh(geometry, material);
field.receiveShadow = true;
field.position.z = -1;
scene.add(field);
/*
* setting up rotation axis
*/
var rotation_matrix = null;
var setQuaternions = function() {
setMatrix();
ball.rotation.set(Math.PI / 2, Math.PI / 4, Math.PI / 4); // Set initial rotation
ball.matrix.makeRotationFromEuler(ball.rotation); // Apply rotation to the object's matrix
}
var setMatrix = function() {
rotation_matrix = new THREE.Matrix4().makeRotationZ(angleRad); // Animated rotation will be in .01 radians along object's X axis
}
setQuaternions();
/*
*
* ANIMATION STEP
*
*/
var render = function(params) {
// add velocity to ball
ball.position.x += velocityX;
ball.position.z += velocityZ;
ball.position.y += velocityY;
//validate if ball is stop moving
if (Math.abs(velocityX) < 0.02 && Math.abs(velocityY) < 0.02) {
console.log("DONE!");
return;
}
// handle boucing effect
if (ball.position.z < 1) {
velocityZ *= -bounciness;
ball.position.z = 1
}
// Update the object's rotation & apply it
/*
ball.matrix.multiply(rotation_matrix); ball.rotation.setFromRotationMatrix(ball.matrix);
//set up the matrix
setMatrix();
*/
// Figure out the rotation based on the velocity and radius of the ball...
ballVelocity.set(velocityX, velocityY, velocityZ);
ballRotationAxis.set(0, 0, 1).cross(ballVelocity).normalize();
var velocityMag = ballVelocity.length();
var rotationAmount = velocityMag * (Math.PI * 2) / ballCircumference;
ball.rotateOnWorldAxis(ballRotationAxis, rotationAmount)
//reducing speed by friction
angleRad *= friction;
velocityX *= friction;
velocityY *= friction;
velocityZ *= friction;
//validate ball is withing its borders otherwise go in the mirror direction
if (Math.abs(ball.position.x) > borders[0]) {
velocityX *= -1;
ball.position.x = (ball.position.x < 0) ? borders[0] * -1 : borders[0];
}
if (Math.abs(ball.position.y) > borders[1]) {
velocityY *= -1;
ball.position.y = (ball.position.y < 0) ? borders[1] * -1 : borders[1];
}
// reduce ball height with gravity
velocityZ -= gravity;
//render the page
renderer.render(scene, camera);
requestAnimationFrame(render);
}
render();
}body {
padding: 0;
margin: 0;
}<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/96/three.min.js"></script>
<html>
<head>
</head>
<body>
</body>
</html>这篇关于THREE.js - 旋转移动 3D 球的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！