Haxe/OpenFL：如何将等长盒体-球体碰撞代码适配为动态尺寸？

你的代码核心问题在于把非正方体盒体错误地近似成了球体（用最大半边长作为等效半径），同时碰撞点的计算逻辑没有考虑盒体各轴尺寸差异。以下是具体修改方案：

关键错误分析 #

1. 碰撞判断逻辑错误：原代码用MathUtils.max(box.size.x*0.5, ...)把盒体当成球体处理，只有正方体时才正确，非正方体下会导致碰撞判断提前或延迟。
2. 碰撞点计算错误：bDeep的计算直接使用盒体整体边长缩放偏移，不符合非正方体盒体的表面碰撞逻辑。

具体修改步骤 #

1. 修正碰撞判断逻辑 #

删除错误的combinedRadius计算，直接比较球体中心到盒体最近点的距离与缩放后的球体半径：

// 替换原碰撞判断代码段
final scaledSphereRadius:Float = sphere.radius * sphereTransform.scale;
final scaledSphereRadiusSquared:Float = scaledSphereRadius * scaledSphereRadius;

// 判断球体是否侵入盒体：最近点距离平方 <= 球体半径平方
if (distanceSquared > scaledSphereRadiusSquared) {
    // 无碰撞
    return new PhysicsCollisionPoints(null, null, null, 0, false);
}

2. 修正碰撞深度计算 #

基于正确的球体半径和实际距离计算碰撞深度：

// 替换原collisionDepth计算
final collisionDepth:Float = scaledSphereRadius - distance;

3. 修正盒体碰撞点（bDeep）计算 #

盒体的碰撞点就是世界空间中的最近点，若要获取侵入后的内部点，需基于碰撞深度偏移：

// 替换原bDeep计算
final bDeep:Vector3D = new Vector3D(
    closestPointOnBox.x - (normal.x * collisionDepth),
    closestPointOnBox.y - (normal.y * collisionDepth),
    closestPointOnBox.z - (normal.z * collisionDepth)
);

4. 进阶优化：支持旋转的非正方体盒体（可选） #

原代码计算boxMin/boxMax的方式仅适用于无旋转的盒体，若要支持带旋转的盒体，需将球体中心转换到盒体局部空间计算最近点：

// 替换原boxMin/boxMax及closestPointOnBox的计算
// 将球体中心转换到盒体局部空间
final boxInverseTransform:Matrix3D = boxTransform.transform.clone();
boxInverseTransform.invert();
final sphereCenterLocal:Vector3D = boxInverseTransform.transformVector(sphereCenter.subtract(boxCenter));

// 局部空间中盒体的半尺寸（轴对齐）
final boxHalfSizeLocal:Vector3D = new Vector3D(
    box.size.x * 0.5,
    box.size.y * 0.5,
    box.size.z * 0.5
);
final boxMinLocal:Vector3D = boxHalfSizeLocal.multiply(-1);
final boxMaxLocal:Vector3D = boxHalfSizeLocal;

// 局部空间内的最近点
final closestPointLocal:Vector3D = new Vector3D(
    MathUtils.clamp(sphereCenterLocal.x, boxMinLocal.x, boxMaxLocal.x),
    MathUtils.clamp(sphereCenterLocal.y, boxMinLocal.y, boxMaxLocal.y),
    MathUtils.clamp(sphereCenterLocal.z, boxMinLocal.z, boxMaxLocal.z)
);

// 转换回世界空间
final closestPointOnBox:Vector3D = boxTransform.transform.transformVector(closestPointLocal).add(boxCenter);

修改后的完整代码 #

public static function TestCollisionBetweenSphereBox(a:PhysicsCollider, ta:PhysicsTransform, b:PhysicsCollider, tb:PhysicsTransform):PhysicsCollisionPoints {
    final sphere:PhysicsSphereCollider = cast(a, PhysicsSphereCollider);
    final sphereTransform = ta;
    final box:PhysicsBoxCollider = cast(b, PhysicsBoxCollider);
    final boxTransform = tb;

    trace("testing collision between sphere", sphere, "and box", box);
    trace("transform", ta, tb);

    // Transform to World Space
    final sphereCenter:Vector3D = new Vector3D(
        sphere.center.x + ta.position.x,
        sphere.center.y + ta.position.y,
        sphere.center.z + ta.position.z
    );

    final boxCenter:Vector3D = new Vector3D(
        box.center.x + tb.position.x,
        box.center.y + tb.position.y,
        box.center.z + tb.position.z
    );

    trace("sphereCenter", sphereCenter);
    trace("boxCenter", boxCenter);

    // 进阶优化：支持旋转的盒体，转换到局部空间计算最近点
    final boxInverseTransform:Matrix3D = boxTransform.transform.clone();
    boxInverseTransform.invert();
    final sphereCenterLocal:Vector3D = boxInverseTransform.transformVector(sphereCenter.subtract(boxCenter));

    final boxHalfSizeLocal:Vector3D = new Vector3D(
        box.size.x * 0.5,
        box.size.y * 0.5,
        box.size.z * 0.5
    );
    final boxMinLocal:Vector3D = boxHalfSizeLocal.multiply(-1);
    final boxMaxLocal:Vector3D = boxHalfSizeLocal;

    final closestPointLocal:Vector3D = new Vector3D(
        MathUtils.clamp(sphereCenterLocal.x, boxMinLocal.x, boxMaxLocal.x),
        MathUtils.clamp(sphereCenterLocal.y, boxMinLocal.y, boxMaxLocal.y),
        MathUtils.clamp(sphereCenterLocal.z, boxMinLocal.z, boxMaxLocal.z)
    );

    final closestPointOnBox:Vector3D = boxTransform.transform.transformVector(closestPointLocal).add(boxCenter);

    trace("closest point", closestPointOnBox);

    // Check for Intersection
    final sphereToBox:Vector3D = closestPointOnBox.subtract(sphereCenter);
    final distanceSquared:Float = sphereToBox.lengthSquared;
    final scaledSphereRadius:Float = sphere.radius * sphereTransform.scale;
    final scaledSphereRadiusSquared:Float = scaledSphereRadius * scaledSphereRadius;

    trace("sphereToBox",sphereToBox);
    trace("distanceSquared", distanceSquared);
    trace("scaledSphereRadius", scaledSphereRadius);
    trace("scaledSphereRadius^2", scaledSphereRadiusSquared);

    if (distanceSquared > scaledSphereRadiusSquared) {
        // No collision
        return new PhysicsCollisionPoints(null, null, null, 0, false);
    }

    // Calculate Collision Points
    final distance:Float = Math.sqrt(distanceSquared);
    final normal:Vector3D = MathUtils.normalizeVector(sphereToBox);

    final collisionDepth:Float = scaledSphereRadius - distance;

    final aDeep:Vector3D = new Vector3D(
        sphereCenter.x + (normal.x * scaledSphereRadius),
        sphereCenter.y + (normal.y * scaledSphereRadius),
        sphereCenter.z + (normal.z * scaledSphereRadius)
    );

    final bDeep:Vector3D = new Vector3D(
        closestPointOnBox.x - (normal.x * collisionDepth),
        closestPointOnBox.y - (normal.y * collisionDepth),
        closestPointOnBox.z - (normal.z * collisionDepth)
    );

    final ret = new PhysicsCollisionPoints(aDeep, bDeep, normal, collisionDepth, true);

    trace("distance", distance);
    trace("normal", normal);
    trace("collisionDepth", collisionDepth);
    trace("aDeep", aDeep);
    trace("bDeep", bDeep);

    return ret;
}

内容的提问来源于stack exchange，提问作者user23323208