Raycasting

最終更新： 2020年1月30日

概述

Raycasting是用于判定用户指定的Cubism网格是否与任意座标相交的功能。
可以获得单击/点击座标、场景中任意物体与指定网格之间的重叠检测。
参考 此处 了解如何使用Raycasting。

Cubism SDK for Unity中的Raycasting包括两个主要元素。

1. 用于指定要判断的图形网格的组件
2. 进行指定输入座标的图形网格重叠检测的组件。

1. 用于指定要判断的图形网格的组件

使用CubismRaycastable指定用于重叠检测的网格。

CubismRaycastable通过附加到置入[Prefab根]/Drawables/下的GameObject来使用。
与附加的GameObject具有相同ID的图形网格将用于重叠检测。

CubismRaycastable具有设置该网格的重叠检测精度的参数。

namespace Live2D.Cubism.Framework.Raycasting
{
    /// <summary>
    /// Allows raycasting against <see cref="Core.CubismDrawable"/>s.
    /// </summary>
    public sealed class CubismRaycastable : MonoBehaviour
    {
        /// <summary>
        /// The precision.
        /// </summary>
        public CubismRaycastablePrecision Precision;
    }
}

CubismRaycastable.Precision有两个可设置的值，每个值如下。

• BoundingBox

包围网格并具有水平或垂直边的矩形用作重叠检测。
根据网格的形状，即使在网格外的座标处也会执行重叠检测，但它比Triangles具有更好的性能。

• Triangles

网格的形状被用作重叠检测的范围。
虽然性能不如BoundingBox，但可以在准确的范围内做出判断。

namespace Live2D.Cubism.Framework.Raycasting
{
    /// <summary>
    /// Precision for casting rays against a <see cref="CubismRaycastable"/>.
    /// </summary>
    public enum CubismRaycastablePrecision
    {
        /// <summary>
        /// Cast against bounding box.
        /// </summary>
        BoundingBox,

        /// <summary>
        /// Cast against triangles.
        /// </summary>
        Triangles
    }
}

2. 进行指定输入座标的图形网格重叠检测的组件。

使用CubismRaycaster获得实际的重叠检测。
使用CubismRaycaster时，将其附加到Cubism的Prefab根部。

当CubismRaycaster原始化时，获取对附加到Prefab的所有CubismRaycastables的参考。
在执行过程中追加/删除重叠检测的网格时，会调用CubismRaycaster.Refresh()再次获取参考。

        /// <summary>
        /// Refreshes the controller. Call this method after adding and/or removing <see cref="CubismRaycastable"/>.
        /// </summary>
        private void Refresh()
        {
            var candidates = this
                .FindCubismModel()
                .Drawables;


            // Find raycastable drawables.
            var raycastables = new List<CubismRenderer>();
            var raycastablePrecisions = new List<CubismRaycastablePrecision>();


            for (var i = 0; i < candidates.Length; i++)
            {
                // Skip non-raycastables.
                if (candidates[i].GetComponent<CubismRaycastable>() == null)
                {
                    continue;
                }


                raycastables.Add(candidates[i].GetComponent<CubismRenderer>());
                raycastablePrecisions.Add(candidates[i].GetComponent<CubismRaycastable>().Precision);
            }


            // Cache raycastables.
            Raycastables = raycastables.ToArray();
            RaycastablePrecisions = raycastablePrecisions.ToArray();
        }

        ...

        /// <summary>
        /// Called by Unity. Makes sure cache is initialized.
        /// </summary>
        private void Start()
        {
            // Initialize cache.
            Refresh();
        }

使用CubismRaycaster.Raycast()从座标中获取重叠检测。

        /// <summary>
        /// Casts a ray.
        /// </summary>
        /// <param name="origin">The origin of the ray.</param>
        /// <param name="direction">The direction of the ray.</param>
        /// <param name="result">The result of the cast.</param>
        /// <param name="maximumDistance">[Optional] The maximum distance of the ray.</param>
        /// <returns><see langword="true"/> in case of a hit; <see langword="false"/> otherwise.</returns>
        /// <returns>The numbers of drawables had hit</returns>
        public int Raycast(Vector3 origin, Vector3 direction, CubismRaycastHit[] result, float maximumDistance = Mathf.Infinity)
        {
            return Raycast(new Ray(origin, direction), result, maximumDistance);
        }

        /// <summary>
        /// Casts a ray.
        /// </summary>
        /// <param name="ray"></param>
        /// <param name="result">The result of the cast.</param>
        /// <param name="maximumDistance">[Optional] The maximum distance of the ray.</param>
        /// <returns><see langword="true"/> in case of a hit; <see langword="false"/> otherwise.</returns>
        /// <returns>The numbers of drawables had hit</returns>
        public int Raycast(Ray ray, CubismRaycastHit[] result, float maximumDistance = Mathf.Infinity)
        {
            // Cast ray against model plane.
            var intersectionInWorldSpace = ray.origin + ray.direction * (ray.direction.z / ray.origin.z);
            var intersectionInLocalSpace = transform.InverseTransformPoint(intersectionInWorldSpace);


            intersectionInLocalSpace.z = 0;


            var distance = intersectionInWorldSpace.magnitude;


            // Return non-hits.
            if (distance > maximumDistance)
            {
                return 0;
            }

            // Cast against each raycastable.
            var hitCount = 0;


            for (var i = 0; i < Raycastables.Length; i++)
            {
                var raycastable = Raycastables[i];
                var raycastablePrecision = RaycastablePrecisions[i];


                // Skip inactive raycastables.
                if (!raycastable.MeshRenderer.enabled)
                {
                    continue;
                }



                if (raycastablePrecision == CubismRaycastablePrecision.BoundingBox)
                {
                    var bounds = raycastable.Mesh.bounds;

                    // Skip non hits
                    if (!bounds.Contains(intersectionInLocalSpace))
                    {
                        continue;
                    }
                }
                else
                {
                    // Skip non hits
                    if (!ContainsInTriangles(raycastable.Mesh, intersectionInLocalSpace))
                    {
                        continue;
                    }
                }


                result[hitCount].Drawable = raycastable.GetComponent<CubismDrawable>();
                result[hitCount].Distance = distance;
                result[hitCount].LocalPosition = intersectionInLocalSpace;
                result[hitCount].WorldPosition = intersectionInWorldSpace;


                ++hitCount;


                // Exit if result buffer is full.
                if (hitCount == result.Length)
                {
                    break;
                }
            }


            return hitCount;
        }

CubismRaycaster.Raycast()在返回值中返回获得重叠检测的网格数。
此外，对于传递给参数的CubismRaycastHit[]类型的副本，设置获得重叠检测的网格信息。

            var raycastResults = new CubismRaycastHit[4];
            var hitCount = _raycaster.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), raycastResults);

当多个网格在同一座标上重叠时，CubismRaycaster.Raycast()会获得CubismRaycastHit[]类型副本的元素数量。
如果超过元素数量的网格重叠，将不会获得超出部分网格的结果。

CubismRaycastHit是包含已获得重叠检测的网格信息的结构。

using Live2D.Cubism.Core;
using UnityEngine;


namespace Live2D.Cubism.Framework.Raycasting
{
    /// <summary>
    /// Contains raycast information.
    /// </summary>
    public struct CubismRaycastHit
    {
        /// <summary>
        /// The hit <see cref="CubismDrawable"/>.
        /// </summary>
        public CubismDrawable Drawable;

        /// <summary>
        /// The distance the ray traveled until it hit the <see cref="CubismDrawable"/>.
        /// </summary>
        public float Distance;

        /// <summary>
        /// The hit position local to the <see cref="CubismDrawable"/>.
        /// </summary>
        public Vector3 LocalPosition;

        /// <summary>
        /// The hit position in world coordinates.
        /// </summary>
        public Vector3 WorldPosition;
    }
}

• Drawable

它是获得重叠检测的图形网格的参考。

• Distance

与指定座标的距离。
传递给CubismRaycaster.Raycast()参数的origin或ray.origin与Drawable的Transform.position之间的线性距离。

• LocalPosition

获得重叠检测的图形网格的局部座标。

• WorldPosition

获得重叠检测的图形网格的世界座标。