CameraGeometry 类

镜头几何计算器，使用高精度数学计算镜头位置。

类概述

package com.liverecorder.util;

public class CameraGeometry {
    private final LiveRecorder plugin;
    private BigDecimal cameraPitch;
    private BigDecimal cameraDistance;
    private BigDecimal heightOffset;
    private BigDecimal followSpeed;
    private BigDecimal arrivalThreshold;
}

获取实例

import com.liverecorder.LiveRecorder;

LiveRecorder lr = (LiveRecorder) Bukkit.getPluginManager().getPlugin("LiveRecorder");
CameraGeometry geometry = lr.getCameraGeometry();

核心方法

calculateCameraLocation()

计算镜头位置。

public Location calculateCameraLocation(Player target)

示例：

Player target = Bukkit.getPlayer("Steve");
Location cameraLoc = geometry.calculateCameraLocation(target);

// cameraLoc 是录制者应该到达的位置
recorder.teleport(cameraLoc);

计算公式：

镜头位置 = 目标玩家位置 + 偏移量

dx = -distance × sin(yaw)                    ← 水平X偏移（身后）
dz =  distance × cos(yaw)                    ← 水平Z偏移
dy =  distance × tan(pitch) + heightOffset   ← 垂直偏移

needsTeleport()

检查是否需要传送。

public boolean needsTeleport(Player recorder, Location cameraTarget, double maxDistance)

示例：

Player recorder = Bukkit.getPlayer("CameraMan");
Location cameraTarget = geometry.calculateCameraLocation(target);

if (geometry.needsTeleport(recorder, cameraTarget, 30.0)) {
    recorder.teleport(cameraTarget);
}

calculateFollowVelocity()

计算跟随速度。

public Location calculateFollowVelocity(Player recorder, Location cameraTarget)

示例：

Player recorder = Bukkit.getPlayer("CameraMan");
Location cameraTarget = geometry.calculateCameraLocation(target);
Location followResult = geometry.calculateFollowVelocity(recorder, cameraTarget);

if (followResult != null) {
    // 计算速度向量
    double vx = followResult.getX() - recorder.getLocation().getX();
    double vy = followResult.getY() - recorder.getLocation().getY();
    double vz = followResult.getZ() - recorder.getLocation().getZ();
    
    recorder.setVelocity(new Vector(vx, vy, vz));
}

配置方法

reload()

重载配置。

public void reload()

示例：

geometry.reload();

内部方法

toRadians()

将角度转换为弧度。

private BigDecimal toRadians(BigDecimal degrees)

sin()

计算正弦值（泰勒级数展开）。

private BigDecimal sin(BigDecimal x)

cos()

计算余弦值（泰勒级数展开）。

private BigDecimal cos(BigDecimal x)

tan()

计算正切值。

private BigDecimal tan(BigDecimal x)

sqrt()

计算平方根（牛顿迭代法）。

private BigDecimal sqrt(BigDecimal x)

使用示例

自定义镜头位置

public Location customCameraLocation(Player target, double pitch, double distance, double heightOffset) {
    Location targetLoc = target.getLocation();
    BigDecimal yawRad = geometry.toRadians(new BigDecimal(String.valueOf(targetLoc.getYaw())));
    
    // 计算水平偏移
    BigDecimal dx = new BigDecimal(String.valueOf(-distance)).multiply(geometry.sin(yawRad), MC);
    BigDecimal dz = new BigDecimal(String.valueOf(distance)).multiply(geometry.cos(yawRad), MC);
    
    // 计算垂直偏移
    BigDecimal pitchRad = geometry.toRadians(new BigDecimal(String.valueOf(pitch)));
    BigDecimal dy = new BigDecimal(String.valueOf(distance))
        .multiply(geometry.tan(pitchRad), MC)
        .add(new BigDecimal(String.valueOf(heightOffset)), MC);
    
    Location cameraLoc = targetLoc.clone();
    cameraLoc.add(dx.doubleValue(), dy.doubleValue(), dz.doubleValue());
    cameraLoc.setDirection(targetLoc.toVector().subtract(cameraLoc.toVector()));
    
    return cameraLoc;
}

检查跟随状态

public void checkFollowStatus(Player recorder, Player target) {
    Location cameraTarget = geometry.calculateCameraLocation(target);
    double distance = recorder.getLocation().distance(cameraTarget);
    
    if (distance > 30.0) {
        // 距离过远，需要传送
        recorder.teleport(cameraTarget);
    } else if (distance > 5.0) {
        // 距离较远，使用速度跟随
        Location followResult = geometry.calculateFollowVelocity(recorder, cameraTarget);
        if (followResult != null) {
            double vx = followResult.getX() - recorder.getLocation().getX();
            double vy = followResult.getY() - recorder.getLocation().getY();
            double vz = followResult.getZ() - recorder.getLocation().getZ();
            recorder.setVelocity(new Vector(vx, vy, vz));
        }
    }
}

计算镜头角度

public double calculateCameraAngle(Player target, Location cameraLoc) {
    Vector direction = target.getLocation().toVector().subtract(cameraLoc.toVector());
    float yaw = (float) Math.toDegrees(Math.atan2(direction.getZ(), direction.getX())) - 90.0f;
    float pitch = (float) -Math.toDegrees(Math.atan2(direction.getY(), Math.sqrt(direction.getX() * direction.getX() + direction.getZ() * direction.getZ())));
    
    return Math.sqrt(yaw * yaw + pitch * pitch);
}

注意事项

高精度计算

CameraGeometry 使用 BigDecimal 进行高精度计算，确保镜头位置准确。

MathContext

内部使用 MathContext(12, RoundingMode.HALF_UP) 确保精度。

性能考虑

镜头计算相对复杂，避免在循环中频繁调用。缓存结果以提高性能。

线程安全

CameraGeometry 的方法是线程安全的，可以在任何线程中调用。

数学原理

泰勒级数展开

三角函数使用泰勒级数展开计算：

sin(x) = x - x³/3! + x⁵/5! - x⁷/7! + ...
cos(x) = 1 - x²/2! + x⁴/4! - x⁶/6! + ...

牛顿迭代法

平方根使用牛顿迭代法计算：

xₙ₊₁ = (xₙ + a/xₙ) / 2

坐标变换

使用标准的 3D 坐标变换公式：

x' = x × cos(θ) - y × sin(θ)
y' = x × sin(θ) + y × cos(θ)