using UnityEngine;

public class GenerateVectorData : MonoBehaviour
{
    private SkinnedMeshRenderer m_mesh;
    private Mesh skinnedMeshCache;
    private Vector3[] vertexFrameCache1;
    private Vector3[] vertexFrameCache2;
    private Vector3[] vertexFrameCache3;
    private ComputeBuffer vertexBuffer1;
    private ComputeBuffer vertexBuffer2;
    private ComputeBuffer vertexBuffer3;
    void Start()
    {
        m_mesh = GetComponent<SkinnedMeshRenderer>();
        skinnedMeshCache = new Mesh();

        //initializing variables and buffers
        m_mesh.BakeMesh(skinnedMeshCache);
        vertexFrameCache1 = m_mesh.sharedMesh.vertices;
        vertexFrameCache2 = m_mesh.sharedMesh.vertices;
        vertexFrameCache3 = m_mesh.sharedMesh.vertices;

        //We use Buffers because we can't send the vertices as is, sending vector arrays to shader needs to be done as Vector4[], and Mesh.Vertices is a Vector3[]. Buffers allow us to bypass this issue
        vertexBuffer1 = new ComputeBuffer(m_mesh.sharedMesh.vertices.Length, 12); //Buffer needs to be the same size as the vertices length and have 3 * 4 (bytes) as size
        vertexBuffer2 = new ComputeBuffer(m_mesh.sharedMesh.vertices.Length, 12);
        vertexBuffer3 = new ComputeBuffer(m_mesh.sharedMesh.vertices.Length, 12);
    }

    void Update()
    {
        //Copying vertex data: this is done from oldest to newest value to keep 4 all frames cached
        vertexFrameCache3 = vertexFrameCache2;
        vertexFrameCache2 = vertexFrameCache1;
        vertexFrameCache1 = skinnedMeshCache.vertices;
        m_mesh.BakeMesh(skinnedMeshCache); //We can't access Skinned mesh data directly, so we need to store the information of the mesh
        
        //Sending vertex information to buffers
        vertexBuffer3.SetData(vertexFrameCache3);
        vertexBuffer2.SetData(vertexFrameCache2);
        vertexBuffer1.SetData(vertexFrameCache1);

        //This could be done per material instead of a global variable, it's just for proof of concept
        Shader.SetGlobalBuffer("_VertexBuffer3", vertexBuffer3);
        Shader.SetGlobalBuffer("_VertexBuffer2", vertexBuffer2);
        Shader.SetGlobalBuffer("_VertexBuffer1", vertexBuffer1);

    }

    void OnDestroy()
    {
        //Make sure to release to avoid GC
        vertexBuffer1.Release();
        vertexBuffer2.Release();
        vertexBuffer3.Release();
    }
}