Unity3d 铰链接头中的无损运动-统一
我已经在Unity中创建了一个单摆-带有刚体和铰链关节组件的游戏对象。我已将“阻力”和“角度阻力”都设置为0。当起始位置为90度时,我希望钟摆能从90度到-90度来回摆动。然而,事实并非如此——振幅衰减非常快,但对于小角度,钟摆看起来永远不会停止 我的问题是:我应该如何配置铰链关节,以实现对物理和抵抗运动的力的完全控制?我的目标是让物理模拟尽可能精确,即使以性能为代价 我已经尝试过减少固定步长和增加解算器迭代的时间间隔,但都没有成功Unity3d 铰链接头中的无损运动-统一,unity3d,physx,Unity3d,Physx,我已经在Unity中创建了一个单摆-带有刚体和铰链关节组件的游戏对象。我已将“阻力”和“角度阻力”都设置为0。当起始位置为90度时,我希望钟摆能从90度到-90度来回摆动。然而,事实并非如此——振幅衰减非常快,但对于小角度,钟摆看起来永远不会停止 我的问题是:我应该如何配置铰链关节,以实现对物理和抵抗运动的力的完全控制?我的目标是让物理模拟尽可能精确,即使以性能为代价 我已经尝试过减少固定步长和增加解算器迭代的时间间隔,但都没有成功 为什么我需要它?我计划设计一个控制系统,用于推车上的多重倒立摆
为什么我需要它?我计划设计一个控制系统,用于推车上的多重倒立摆。我有一个用Matlab实现的摆锤数学模型,我想用Unity中的一个简单模型来验证它(因为在这种情况下,我调整了所有参数、初始条件等,物理引擎正在为我计算一切)。如果支持Unity的物理引擎不够可靠,你会推荐我其他什么软件?我的理解是,由于Unity的物理运行方式,如果你只使用铰链关节,这种摆锤运动会随着时间的推移而损失动能。基本上,如果你想要一个精确的钟摆模拟,你必须绕过物理引擎,直接实现它 最初,作者发布了一篇关于如何在Unity中实现更精确的钟摆模拟的文章,我将其粘贴在下面
我原以为这是一个相对简单的问题要解决,但我花了几天时间试图弄清楚如何模拟钟摆运动。我不想作弊,只是根据sin(θ)和cos(θ)曲线改变x,y的位置。相反,我想处理现实生活中应用的两种力,重力和张力。我缺少的主要部分是向心力 有一个很好的动画(下图,左侧)解释了钟摆的运动。您可以看到我的结果(右侧)与该图惊人地相似 “bob”是摆动对象,“pivot”是原点/根 我还发现和图表(如下)非常有用:
θ等于绳索与重力方向之间的角度 当摆锤位于左侧或右侧时,张力等于: 当摆锤接近平衡点(中间)时,张力更大的原因是: 因此,当摆锤摆动时,覆盖张力公式如下所示: 摆锤系统中有两个力:
- 重力
GravityForce=质量*重力.量级
GravityDirection=gravity.normalized
- 紧张
TensionForce=(质量*重力*Cos(θ))+((质量*速度变化^2)/缆绳长度)
TensionDirection=rope direction=bob到枢轴
Update()
函数,了解我是如何实现它的
使用UnityEngine;
使用系统集合;
//作者:埃里克·伊斯特伍德(ericestwood.com)
//
//说明:
//针对本gd.se问题编写:http://gamedev.stackexchange.com/a/75748/16587
//在代码中模拟/仿真摆锤运动
//在任何3D方向和任何重力/方向下工作
//
//演示:https://i.imgur.com/vOQgFMe.gif
//
//用法:https://i.imgur.com/BM52dbT.png
公共类钟摆:单一行为{
公共游戏对象轴心;
公共游戏对象Bob;
公共浮子质量=1f;
浮绳长度=2f;
矢量3开始位置;
bool bobStartingPositionSet=false;
//您可以在'PendulumUpdate()'循环中定义这些
//但是我们希望它们在类范围内,这样我们就可以绘制gizmo`OnDrawGizmos()`
私人矢量3引力方向;
专用矢量3张紧方向;
专用矢量3切向;
私人矢量3摆动方向;
专用浮子拉力=0f;
专用浮子重力力=0f;
//跟踪流速
Vector3 currentVelocity=新Vector3();
//在“Update()”循环中的某些帧速率情况下,我们使用这些参数在值之间平滑
矢量3当前状态位置;
向量3先前状态位置;
//用于初始化
无效开始(){
//设置起始位置,以便以后在上下文菜单重置方法中使用
this.bobStartingPosition=this.Bob.transform.position;
this.bobStartingPositionSet=true;
这个。摆();
}
浮动t=0f;
浮子dt=0.01f;
浮动电流时间=0f;
浮子蓄能器=0f;
无效更新()
{
/* */
//修复了使用平滑在任意速度下进行deltaTime渲染的问题
//技术:http://gafferongames.com/game-physics/fix-your-timestep/
using UnityEngine;
using System.Collections;
// Author: Eric Eastwood (ericeastwood.com)
//
// Description:
// Written for this gd.se question: http://gamedev.stackexchange.com/a/75748/16587
// Simulates/Emulates pendulum motion in code
// Works in any 3D direction and with any force/direciton of gravity
//
// Demonstration: https://i.imgur.com/vOQgFMe.gif
//
// Usage: https://i.imgur.com/BM52dbT.png
public class Pendulum : MonoBehaviour {
public GameObject Pivot;
public GameObject Bob;
public float mass = 1f;
float ropeLength = 2f;
Vector3 bobStartingPosition;
bool bobStartingPositionSet = false;
// You could define these in the `PendulumUpdate()` loop
// But we want them in the class scope so we can draw gizmos `OnDrawGizmos()`
private Vector3 gravityDirection;
private Vector3 tensionDirection;
private Vector3 tangentDirection;
private Vector3 pendulumSideDirection;
private float tensionForce = 0f;
private float gravityForce = 0f;
// Keep track of the current velocity
Vector3 currentVelocity = new Vector3();
// We use these to smooth between values in certain framerate situations in the `Update()` loop
Vector3 currentStatePosition;
Vector3 previousStatePosition;
// Use this for initialization
void Start () {
// Set the starting position for later use in the context menu reset methods
this.bobStartingPosition = this.Bob.transform.position;
this.bobStartingPositionSet = true;
this.PendulumInit();
}
float t = 0f;
float dt = 0.01f;
float currentTime = 0f;
float accumulator = 0f;
void Update()
{
/* */
// Fixed deltaTime rendering at any speed with smoothing
// Technique: http://gafferongames.com/game-physics/fix-your-timestep/
float frameTime = Time.time - currentTime;
this.currentTime = Time.time;
this.accumulator += frameTime;
while (this.accumulator >= this.dt)
{
this.previousStatePosition = this.currentStatePosition;
this.currentStatePosition = this.PendulumUpdate(this.currentStatePosition, this.dt);
//integrate(state, this.t, this.dt);
accumulator -= this.dt;
this.t += this.dt;
}
float alpha = this.accumulator/this.dt;
Vector3 newPosition = this.currentStatePosition*alpha + this.previousStatePosition*(1f-alpha);
this.Bob.transform.position = newPosition; //this.currentStatePosition;
/* */
//this.Bob.transform.position = this.PendulumUpdate(this.Bob.transform.position, Time.deltaTime);
}
// Use this to reset forces and go back to the starting position
[ContextMenu("Reset Pendulum Position")]
void ResetPendulumPosition()
{
if(this.bobStartingPositionSet)
this.MoveBob(this.bobStartingPosition);
else
this.PendulumInit();
}
// Use this to reset any built up forces
[ContextMenu("Reset Pendulum Forces")]
void ResetPendulumForces()
{
this.currentVelocity = Vector3.zero;
// Set the transition state
this.currentStatePosition = this.Bob.transform.position;
}
void PendulumInit()
{
// Get the initial rope length from how far away the bob is now
this.ropeLength = Vector3.Distance(Pivot.transform.position, Bob.transform.position);
this.ResetPendulumForces();
}
void MoveBob(Vector3 resetBobPosition)
{
// Put the bob back in the place we first saw it at in `Start()`
this.Bob.transform.position = resetBobPosition;
// Set the transition state
this.currentStatePosition = resetBobPosition;
}
Vector3 PendulumUpdate(Vector3 currentStatePosition, float deltaTime)
{
// Add gravity free fall
this.gravityForce = this.mass * Physics.gravity.magnitude;
this.gravityDirection = Physics.gravity.normalized;
this.currentVelocity += this.gravityDirection * this.gravityForce * deltaTime;
Vector3 pivot_p = this.Pivot.transform.position;
Vector3 bob_p = this.currentStatePosition;
Vector3 auxiliaryMovementDelta = this.currentVelocity * deltaTime;
float distanceAfterGravity = Vector3.Distance(pivot_p, bob_p + auxiliaryMovementDelta);
// If at the end of the rope
if(distanceAfterGravity > this.ropeLength || Mathf.Approximately(distanceAfterGravity, this.ropeLength))
{
this.tensionDirection = (pivot_p - bob_p).normalized;
this.pendulumSideDirection = (Quaternion.Euler(0f, 90f, 0f) * this.tensionDirection);
this.pendulumSideDirection.Scale(new Vector3(1f, 0f, 1f));
this.pendulumSideDirection.Normalize();
this.tangentDirection = (-1f * Vector3.Cross(this.tensionDirection, this.pendulumSideDirection)).normalized;
float inclinationAngle = Vector3.Angle(bob_p-pivot_p, this.gravityDirection);
this.tensionForce = this.mass * Physics.gravity.magnitude * Mathf.Cos(Mathf.Deg2Rad * inclinationAngle);
float centripetalForce = ((this.mass * Mathf.Pow(this.currentVelocity.magnitude, 2))/this.ropeLength);
this.tensionForce += centripetalForce;
this.currentVelocity += this.tensionDirection * this.tensionForce * deltaTime;
}
// Get the movement delta
Vector3 movementDelta = Vector3.zero;
movementDelta += this.currentVelocity * deltaTime;
//return currentStatePosition + movementDelta;
float distance = Vector3.Distance(pivot_p, currentStatePosition + movementDelta);
return this.GetPointOnLine(pivot_p, currentStatePosition + movementDelta, distance <= this.ropeLength ? distance : this.ropeLength);
}
Vector3 GetPointOnLine(Vector3 start, Vector3 end, float distanceFromStart)
{
return start + (distanceFromStart * Vector3.Normalize(end - start));
}
void OnDrawGizmos()
{
// purple
Gizmos.color = new Color(.5f, 0f, .5f);
Gizmos.DrawWireSphere(this.Pivot.transform.position, this.ropeLength);
Gizmos.DrawWireCube(this.bobStartingPosition, new Vector3(.5f, .5f, .5f));
// Blue: Auxilary
Gizmos.color = new Color(.3f, .3f, 1f); // blue
Vector3 auxVel = .3f * this.currentVelocity;
Gizmos.DrawRay(this.Bob.transform.position, auxVel);
Gizmos.DrawSphere(this.Bob.transform.position + auxVel, .2f);
// Yellow: Gravity
Gizmos.color = new Color(1f, 1f, .2f);
Vector3 gravity = .3f * this.gravityForce*this.gravityDirection;
Gizmos.DrawRay(this.Bob.transform.position, gravity);
Gizmos.DrawSphere(this.Bob.transform.position + gravity, .2f);
// Orange: Tension
Gizmos.color = new Color(1f, .5f, .2f); // Orange
Vector3 tension = .3f * this.tensionForce*this.tensionDirection;
Gizmos.DrawRay(this.Bob.transform.position, tension);
Gizmos.DrawSphere(this.Bob.transform.position + tension, .2f);
// Red: Resultant
Gizmos.color = new Color(1f, .3f, .3f); // red
Vector3 resultant = gravity + tension;
Gizmos.DrawRay(this.Bob.transform.position, resultant);
Gizmos.DrawSphere(this.Bob.transform.position + resultant, .2f);
/* * /
// Green: Pendulum side direction
Gizmos.color = new Color(.3f, 1f, .3f);
Gizmos.DrawRay(this.Bob.transform.position, 3f*this.pendulumSideDirection);
Gizmos.DrawSphere(this.Bob.transform.position + 3f*this.pendulumSideDirection, .2f);
/* */
/* * /
// Cyan: tangent direction
Gizmos.color = new Color(.2f, 1f, 1f); // cyan
Gizmos.DrawRay(this.Bob.transform.position, 3f*this.tangentDirection);
Gizmos.DrawSphere(this.Bob.transform.position + 3f*this.tangentDirection, .2f);
/* */
}
}