【动画】unity中实现骨骼蒙皮动画

我是一名资深的游戏客户端，没事的时候我就想手搓轮子

本文目标

搓一个骨骼动画的核心实现，促进理解骨骼动画本质

骨骼动画简介

官方解释上网搜或者问豆包

快速理解

想知道骨骼动画怎么个事要先知道模型是怎么个事
简单来说：模型 = 顶点数据 + 三角形 + 材质
骨骼动画 = 模型 + 骨骼权重数据
骨骼权重数据是编辑器下由美术编辑出来的数据，指明某个顶点受到几根骨骼影响，每个骨骼权重是什么
在unity里，骨骼就是transform

思路

• 在unity里自己实现一个组件，自己做骨骼对顶点的影响，完成蒙皮
• 骨骼的transform驱动还靠unity的Animation，在自己的组件里获取骨骼transform就够了
• 参照SkinnedMeshRenderer设计自己的组件
• 骨骼动画核心公式，求顶点位置：skinnedVertex = 加权求和(骨骼local2world矩阵 * 顶点初始位置矩阵 * vertex * weight)
• 只要能拿到顶点，骨骼transform，顶点初始位置矩阵，权重数据，就可以求出来模型某个顶点在动画中某一帧的位置

准备数据

• 模型，fbx模型文件的mesh
• 获取骨骼

深度遍历根骨骼的子节点是不行的，里面有用不上的transform不是骨骼，得解析fbx模型文件
FBX模型文件里有骨骼数据形如：Deformer: "SubDeformer::Cluster DummyMesh B-hips", "Cluster"
解析fbx费事，不是核心代码，用SkinnedMeshRenderer的接口bones获取

• 权重数据，用Mesh的boneWeights接口，一个顶点最多受到4个骨骼影响，基本够用
• 顶点初始位置矩阵，用Mesh的bindposes接口获得

开搓

using UnityEngine;namespace HotPlayer.Demos
{[ExecuteInEditMode]public class HotSkinnedMeshRenderer : MonoBehaviour{public Mesh mesh;public Material material;public bool castShadow = true;public bool receiveShadow = true;public bool useLightProbes = true;private Mesh skinnedMesh;private Vector3[] vertices;private BoneWeight[] boneWeights;private Transform[] bones;void Start(){skinnedMesh = Instantiate(mesh);skinnedMesh.name = mesh.name + "_Skinned";boneWeights = skinnedMesh.boneWeights;vertices = skinnedMesh.vertices;bones = gameObject.GetComponent<SkinnedMeshRenderer>().bones;}private void OnDestroy(){if (skinnedMesh != null){if (Application.isPlaying){Destroy(skinnedMesh);}else{DestroyImmediate(skinnedMesh);}}}private void UpdateVertices(){for (var i = 0; i < boneWeights.Length; i++){BoneWeight boneWeight = boneWeights[i];Vector3 vertex = mesh.vertices[i];Vector3 skinnedVertex = Vector3.zero;var index = boneWeight.boneIndex0;Transform bone;if (index > 0){bone = bones[index];var boneMatrix = bone.localToWorldMatrix * mesh.bindposes[index];skinnedVertex += boneMatrix.MultiplyPoint3x4(vertex) * boneWeight.weight0;}index = boneWeight.boneIndex1;if (index > 0){bone = bones[index];var boneMatrix = bone.localToWorldMatrix * mesh.bindposes[index];skinnedVertex += boneMatrix.MultiplyPoint3x4(vertex) * boneWeight.weight1;}index = boneWeight.boneIndex2;if (index > 0){bone = bones[index];var boneMatrix = bone.localToWorldMatrix * mesh.bindposes[index];skinnedVertex += boneMatrix.MultiplyPoint3x4(vertex) * boneWeight.weight2;}index = boneWeight.boneIndex3;if (index > 0){bone = bones[index];var boneMatrix = bone.localToWorldMatrix * mesh.bindposes[index];skinnedVertex += boneMatrix.MultiplyPoint3x4(vertex) * boneWeight.weight3;}vertices[i] = skinnedVertex;}skinnedMesh.vertices = vertices;skinnedMesh.RecalculateBounds();skinnedMesh.RecalculateNormals();}void Update(){#if UNITY_EDITORif (Application.isPlaying)DrawSkinMesh();elseGraphics.DrawMesh(mesh, transform.localToWorldMatrix, material, 0, null, 0, null, castShadow, receiveShadow, useLightProbes);
#elseDrawSkinMesh();
#endif}private void DrawSkinMesh(){UpdateVertices();Graphics.DrawMesh(skinnedMesh, transform.localToWorldMatrix, material, 0, null, 0, null, castShadow, receiveShadow, useLightProbes);}}
}

结语

点赞超64就再搓一个GPU版骨骼蒙皮动画

所以说学习好啊，得学啊，因为真男人必会手搓轮子