Showcase How to write world position to SkinnedMeshRenderer under pose

This was a rather tricky issue I couldn't find much help for, so I didn't want to let the solution go without some coverage:
I wanted to edit the mesh under a SkinnedMeshRenderer, in order to move its vertices to a determined world position, but do this while the bones are in a non-default pose. To do this you need the inverse of a bone transformation, which requires you to add and multiply matrices together, annoyingly Unity's builtin Matrix4x4 doesn't have methods for this, so a little hack included.

Code (CSharp):

1.  
2. public SkinnedMeshRenderer smr;
3.  
4. private void SetMeshAtCurrentPose() {
5.  
6.         Transform[] bones = smr.bones;
7.  
8.         int vertexCount = smr.sharedMesh.vertexCount;
9.         Vector3[] vertices = new Vector3[vertexCount];
10.  
11.         Matrix4x4[] bt = new Matrix4x4[bones.Length];
12.         Matrix4x4[] bindPoses = smr.sharedMesh.bindposes;
13.         for (int i = 0; i < bones.Length; i++)
14.             bt[i] = bones[i].localToWorldMatrix * bindPoses[i];
15.  
16.         BoneWeight[] bws = smr.sharedMesh.boneWeights;
17.  
18.         for (int i = 0; i < vertexCount; i++) {
19.             BoneWeight bw = bws[i];
20.             Vector4[] vecForm = new Vector4[4];
21.             LinComb(vecForm, bt[bw.boneIndex0], bw.weight0);
22.             LinComb(vecForm, bt[bw.boneIndex1], bw.weight1);
23.             LinComb(vecForm, bt[bw.boneIndex2], bw.weight2);
24.             LinComb(vecForm, bt[bw.boneIndex3], bw.weight3);
25.             Matrix4x4 ibt = new Matrix4x4(vecForm[0], vecForm[1], vecForm[2], vecForm[3]).inverse;
26.  
27.             Vector3 v = //Desired world position here
28.             vertices[i] = ibt.MultiplyPoint3x4(v);
29.         }
30.  
31.         Mesh posedMesh = Instantiate(smr.sharedMesh);
32.         posedMesh.vertices = vertices;
33.         smr.sharedMesh = posedMesh;
34.     }
35.  
36.     private static void LinComb(Vector4[] lc, Matrix4x4 mat, float scalar) {
37.         for (int i = 0; i < 4; i++)
38.             lc[i] += scalar * mat.GetColumn(i);
39.     }
40.