beyond/Assets/Scripts/Effects/WeaponTrail.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;

namespace Beyond
{
    [RequireComponent(typeof(MeshFilter))]
    [RequireComponent(typeof(MeshRenderer))]
    [DisallowMultipleComponent]
    public class WeaponTrail : MonoBehaviour
    {
        [SerializeField] private Transform m_tip;
        [SerializeField] private Transform m_base;
        private Mesh m_mesh;
        [SerializeField] private int m_numFrames = 10;

        private Transform m_parentWeapon;
        private const int NUM_VERTICES = 2;
        private int m_frameNum = 0;
        private int m_triNum = 0;

        private int[] m_triangles;
        private Vector3[] m_vertices;
        private Color[] m_colours;
        private bThirdPersonInput m_tpInput;
        private Renderer m_renderer;

        private const int NUM_PREV_POINTS = 3;
        private Vector3[] m_prevTip = new Vector3[NUM_PREV_POINTS], m_prevBase = new Vector3[NUM_PREV_POINTS];

        [SerializeField] private int m_maxDivisions = 4;
        [SerializeField] private float m_stripLength = 0.1f;

        [ColorUsageAttribute(true, true, 0f, 8f, 0.125f, 3f)]
        public Color m_colorMultiplier = Color.white;
        public bool m_alwaysPlay = true; 
        // Start is called before the first frame update
        void Start()
        {
            m_tpInput = Player.Instance.GetComponent<bThirdPersonInput>();
           // transform.parent = null;
            var meshFilter = GetComponent<MeshFilter>();
            m_renderer = GetComponent<MeshRenderer>();
            m_mesh = new Mesh();
            m_renderer.shadowCastingMode = ShadowCastingMode.Off;
            m_mesh.MarkDynamic();
            meshFilter.mesh = m_mesh;

            m_tip.transform.parent = transform.parent;
            m_base.transform.parent = transform.parent;
            m_parentWeapon = transform.parent;
            transform.parent = null;
            transform.position = Vector3.zero;
            transform.rotation = Quaternion.identity;
            transform.localScale = Vector3.one;

            for (int i = 0; i < NUM_PREV_POINTS; i++)
            {
                m_prevTip[i] = m_tip.transform.position;
                m_prevBase[i] = m_base.transform.position;
            }

            //m_vertices = new Vector3[m_numFrames * NUM_VERTICES];
            m_vertices = new Vector3[m_numFrames * NUM_VERTICES];
            m_colours = new Color[m_vertices.Length];
            m_triangles = new int[(m_numFrames-1) * 6];
            var basePos = m_base.transform.position;
            var tipPos = m_tip.transform.position;

            for (int i = 0; i < m_numFrames; i++)
            {
                int vdx = i * NUM_VERTICES;
                m_vertices[vdx + 0] = basePos;
                m_vertices[vdx + 1] = tipPos;
            }

            int numV = m_vertices.Length;
            
            for (int i = 0; i < m_numFrames-1; i++)
            {
                int vdx = i * NUM_VERTICES;
                int tdx = i * 6;
                
                int v2 = (vdx + 2 )% numV;
                int v3 = (vdx + 3 )% numV;
                //int v2 = (vdx - 2 );//% numV;
                //int v3 = (vdx - 1 );//% numV;
                //if (v2 < 0) v2 += numV;
                //if (v3 < 0) v3 += numV;

                m_triangles[tdx + 0] = vdx + 0;
                m_triangles[tdx + 1] = vdx + 1;
                m_triangles[tdx + 2] = v2;
                m_triangles[tdx + 3] = v2;
                m_triangles[tdx + 4] = v3;
                m_triangles[tdx + 5] = vdx + 1;
            }

           // m_mesh.vertices = m_vertices;
           // m_mesh.triangles = m_triangles;

        }

        Vector3 CatmullRom(Vector3 p1, Vector3 p2, Vector3 p3, Vector3 p4, float s)
        {
            Vector3 res;
            float s2, s3;
            s2 = s * s;
            s3 = s2 * s;
            res = p1 * (-s3 + 2.0f * s2 - s) + p2 * (3.0f * s3 - 5.0f * s2 + 2.0f) + p3 * (-3.0f * s3 + 4.0f * s2 + s) + p4 * (s3 - s2);
            res /= 2.0f;
            return res;
        }
        
        bool PlayConditions()
        {
             bool playConditions =  m_tpInput.cc.IsAnimatorTag("Attack") && m_parentWeapon.gameObject.activeInHierarchy;
             return playConditions;
        }
        /*
        void Update()
        {
            bool shouldPlay = PlayConditions() || m_alwaysPlay;
            m_renderer.enabled = shouldPlay;
            var basePos = m_base.transform.position;
            var tipPos = m_tip.transform.position;
 
            
            if (!shouldPlay)
            {
                for (int i = 0; i < NUM_PREV_POINTS; i++)
                {
                    m_prevBase[i] = basePos;
                    m_prevTip[i] = tipPos;
                }
            }
            else
            {
                Debug.Log("Attack!");
            }
            
            
            int numV = m_vertices.Length;

            int idx = m_frameNum * NUM_VERTICES;
            if (m_numDivisions > 1)
            {
                for (int d = 0; d < m_numDivisions; d++ )
                {
                    idx = m_frameNum * NUM_VERTICES;
                    float t = (float) d / (float) m_numDivisions;
                    m_vertices[idx + 0] = CatmullRom(m_prevBase[1], m_prevBase[0], basePos, basePos, t);
                    m_vertices[idx + 1] = CatmullRom(m_prevTip[1], m_prevTip[0], tipPos, tipPos, t);
                    
                    int tdx = m_frameNum * 6;
                    //int v2 = (idx + 2 );//% numV;
                    //int v3 = (idx + 3 );//% numV;
                    int v2 = (idx - 2 );//% numV;
                    int v3 = (idx - 1 );//% numV;
                    if (v2 < 0) v2 += numV;
                    if (v3 < 0) v3 += numV;
                
                    m_triangles[tdx + 0] = idx + 0;
                    m_triangles[tdx + 1] = idx + 1;
                    m_triangles[tdx + 2] = v2;
                    m_triangles[tdx + 3] = v2;
                    m_triangles[tdx + 4] = v3;
                    m_triangles[tdx + 5] = idx + 1;
                    
                    
                    m_frameNum++;
                    m_frameNum %= m_numFrames;
                }
            }
            else
            {
                m_vertices[idx + 0] = basePos;
                m_vertices[idx + 1] = tipPos;
                m_vertices[idx + 2] = m_prevBase[0];
                m_vertices[idx + 3] = m_prevTip[0];
                int tdx = m_frameNum * 6;
       
                int v2 = (idx +2 );//% numV;
                int v3 = (idx +3 );//% numV;
                if (v2 < 0) v2 += numV;
                if (v3 < 0) v3 += numV;
                
                m_triangles[tdx + 0] = idx + 0;
                m_triangles[tdx + 1] = idx + 1;
                m_triangles[tdx + 2] = v2;
                m_triangles[tdx + 3] = v2;
                m_triangles[tdx + 4] = v3;
                m_triangles[tdx + 5] = idx + 1;
                m_frameNum++;
                m_frameNum %= m_numFrames;

            }

            //fill colours
            Color colour = Color.white;
            for (int i = 0; i < m_numFrames; i++)
            {
                //colour.a = (float) (i) / ((float) m_numFrames);
                colour.a = (float) (m_numFrames - i) / ((float) m_numFrames);
                int cnum = (m_frameNum - i) % m_numFrames;
                if (cnum < 0) cnum += m_numFrames;
                int cid = (cnum * NUM_VERTICES);
                for (int j = 0; j < NUM_VERTICES; j++)
                {
                    m_colours[cid + j] = colour;
                }
            }
            

            m_mesh.vertices = m_vertices;
            m_mesh.colors = m_colours;
            //m_mesh.
            m_mesh.triangles = m_triangles;
            m_mesh.RecalculateBounds();

            for (int i = 0; i < NUM_PREV_POINTS - 1; i++)
            {
                m_prevTip[i + 1] = m_prevTip[i];
                m_prevBase[i + 1] = m_prevBase[i];
            }
            m_prevTip[0] = tipPos;
            m_prevBase[0] = basePos;
            
        }
        */
        // Update is called once per frame
        void AddStrip(Vector3 basePos, Vector3 tipPos)
        {
            int numV = m_vertices.Length;
            int idx = m_frameNum * NUM_VERTICES;

            m_vertices[idx + 0] = basePos;
            m_vertices[idx + 1] = tipPos;

            int tidx = m_triNum * 6;
 
            int v2 = (idx - 2);
            int v3 = (idx - 1);
            if (v2 < 0) v2 += numV;
            if (v3 < 0) v3 += numV;
                
            m_triangles[tidx + 0] = idx + 0;
            m_triangles[tidx + 1] = idx + 1;
            m_triangles[tidx + 2] = v2;
            m_triangles[tidx + 3] = v2;
            m_triangles[tidx + 4] = v3;
            m_triangles[tidx + 5] = idx + 1;
                
            m_frameNum++;
            m_frameNum %= m_numFrames;
            m_triNum++;
            m_triNum %= (m_numFrames - 1);
        }
        void FixedUpdate()
        {
            bool shouldPlay = PlayConditions() || m_alwaysPlay;
            
            m_renderer.enabled = shouldPlay;
            var basePos = m_base.transform.position;
            var tipPos = m_tip.transform.position;
 
            
            if (!shouldPlay)
            {
                if (Player.Instance.ActiveWeaponTrail == this)
                {
                    Player.Instance.ActiveWeaponTrail = null;
                }
                
                for (int i = 0; i < NUM_PREV_POINTS; i++)
                {
                    m_prevBase[i] = basePos;
                    m_prevTip[i] = tipPos;
                }
                AddStrip(basePos, tipPos);
                return;
            }
            else
            {
                Player.Instance.ActiveWeaponTrail = this;
                //Debug.Log("Attack!");
            }
            
            
            int numV = m_vertices.Length;

            int idx = m_frameNum * NUM_VERTICES;
            if (m_maxDivisions > 1)
            {
                float bdist = Vector3.Distance(m_prevBase[0], basePos);
                float tdist = Vector3.Distance(m_prevTip[0], tipPos);
                float dist = Mathf.Max(bdist, tdist);
                int div = Mathf.CeilToInt(dist / m_stripLength);
                div = Math.Min(div, m_maxDivisions);
                //Debug.Log("Divisions: "+div);
                for (int d = 0; d < div; d++ )
                {
                    float t = (float) d / (float) div;
                    //var bp = CatmullRom(m_prevBase[1], m_prevBase[0], basePos, basePos, t);
                    //var tp = CatmullRom(m_prevTip[1], m_prevTip[0], tipPos, tipPos, t);
                    var bp = CatmullRom(m_prevBase[2], m_prevBase[1], m_prevBase[0], basePos, t);
                    var tp = CatmullRom(m_prevTip[2], m_prevTip[1], m_prevTip[0], tipPos, t);
                    AddStrip(bp, tp);
                   
                }
            }
            else
            {

                AddStrip(basePos, tipPos);
            }

            //fill colours
            Color colour = m_colorMultiplier;
            for (int i = 0; i < m_numFrames; i++)
            {
                //colour.a = (float) (i) / ((float) m_numFrames);
                colour.a = (float) (m_numFrames - i) / ((float) m_numFrames);
                int cnum = (m_frameNum - i-1) % m_numFrames;
                if (cnum < 0) cnum += m_numFrames;
                int cid = (cnum * NUM_VERTICES);
                for (int j = 0; j < NUM_VERTICES; j++)
                {
                    m_colours[cid + j] = colour;
                }
            }
            

            m_mesh.vertices = m_vertices;
            m_mesh.colors = m_colours;
            //m_mesh.
            m_mesh.triangles = m_triangles;
            m_mesh.RecalculateBounds();

            for (int i = 0; i < NUM_PREV_POINTS - 1; i++)
            {
                m_prevTip[i + 1] = m_prevTip[i];
                m_prevBase[i + 1] = m_prevBase[i];
            }
            m_prevTip[0] = tipPos;
            m_prevBase[0] = basePos;
            
        }
    }
}