From 4756f47d587eaf8db5b54118d0ed7cbdadad403d Mon Sep 17 00:00:00 2001
From: chai <chaifix@163.com>
Date: Wed, 12 May 2021 14:06:59 +0800
Subject: +model tangent normal viwer

---
 UnityCollection/Assets/Tools/ModelTBNShow.cs | 89 ++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 UnityCollection/Assets/Tools/ModelTBNShow.cs

(limited to 'UnityCollection/Assets/Tools/ModelTBNShow.cs')

diff --git a/UnityCollection/Assets/Tools/ModelTBNShow.cs b/UnityCollection/Assets/Tools/ModelTBNShow.cs
new file mode 100644
index 0000000..a1f431c
--- /dev/null
+++ b/UnityCollection/Assets/Tools/ModelTBNShow.cs
@@ -0,0 +1,89 @@
+// 显示模型的normal, tangnent, binormal
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class ModelTBNShow : MonoBehaviour
+{
+    [Range(0f, 10f)]
+    public float tbnLen = 0.1f;
+    [Range(0, 1000)]
+    public int maxShowNum = 100;
+    public bool showNormal = true;
+    public bool showTangent = true;
+    public bool showBiTangent = true;
+
+    MeshFilter meshFilter;
+    Mesh sharedMesh;
+
+    Matrix4x4 localToWorld;
+    Matrix4x4 localToWorldInverseTranspose;
+
+    private void OnDrawGizmos()
+    {
+        meshFilter = GetComponent<MeshFilter>();
+        sharedMesh = meshFilter.sharedMesh;
+
+        localToWorld = meshFilter.transform.localToWorldMatrix;
+        localToWorldInverseTranspose = localToWorld.inverse.transpose;
+
+        Vector3[] vertices = sharedMesh.vertices;
+        Vector3[] normals = sharedMesh.normals;
+        Vector4[] tangents = sharedMesh.tangents;
+
+        int tangentsLen = (tangents != null ? tangents.Length : 0);
+        Vector3[] biTangents = new Vector3[tangentsLen];
+        Vector3[] tangentsData = new Vector3[tangentsLen];
+        for (int i = 0; i < tangentsLen; i++)
+        {
+            //切向量数据 Vector4 转 Vector3
+            tangentsData[i].x = tangents[i].x;
+            tangentsData[i].y = tangents[i].y;
+            tangentsData[i].z = tangents[i].z;
+            //计算副切线 cross(法向量，切向量)*坐标系方向参数
+            biTangents[i] = Vector3.Cross(normals[i], tangentsData[i]) * tangents[i].w;
+        }
+
+        /*
+         * localToWorld 将 顶点位置 从模型坐标系转到世界坐标系矩阵
+         * localToWorldInverseTranspose 将 向量 从模型坐标系转到世界坐标系矩阵
+         *      1、切向量t和副切向量b 由于方向与纹理坐标系一致 使用localToWorld和localToWorldInverseTranspose矩阵转换到世界坐标系 结果相同
+         *      2、normal 由于模型有非等比缩放的情况，缩放后顶点的法向量使用localToWorld矩阵转换的结果不正确
+         *      设矩阵M为切向量t的转换矩阵,矩阵G为法向量n的转换矩阵,
+         *      转换后的切向量且t2 = M*t， 转换后的法向量n2 = G*n，同时要求 n2 * t2 = 0
+         *      所以  (G*n)' * (M*t) = 0  =>  n'*G'*M*t = 0  (n'表示向量n的转置, G'表示矩阵G的转置)
+         *      已知 n'*t = 0(法向量和切向量垂直)， 此时如果令 G'*M = I(单位矩阵)
+         *      则有 n'*G'*M*t = n'*I*t = n'*t = 0 成立
+         *      可得 G'*M = I => G = (inverse(M))'
+         */
+        if (showNormal) DrawVectors(vertices, normals, ref localToWorld, ref localToWorldInverseTranspose, Color.red, tbnLen);
+        if (showTangent) DrawVectors(vertices, tangentsData, ref localToWorld, ref localToWorld, Color.green, tbnLen);
+        if (showBiTangent) DrawVectors(vertices, biTangents, ref localToWorld, ref localToWorld, Color.blue, tbnLen);
+    }
+
+    /*显示向量
+     * vertexs 向量初始位置
+     * vectors 向量方向
+     * vertexMatrix 向量初始位置从模型坐标系转到世界坐标系矩阵
+     * vectorMatrix 向量方向从模型坐标系转到世界坐标系矩阵
+     * color 向量颜色
+     * */
+    void DrawVectors(Vector3[] vertexs, Vector3[] vectors, ref Matrix4x4 vertexMatrix, ref Matrix4x4 vectorMatrix, Color color, float vectorLen)
+    {
+        Gizmos.color = color;
+        int len = (vertexs == null || vectors == null ? 0 : vertexs.Length);
+        len = Mathf.Min(len, maxShowNum);
+        if (vertexs.Length != vectors.Length)
+        {
+            Debug.LogError("vertexs lenght not equal vectors length!!!");
+            return;
+        }
+        for (int i = 0; i < len; i++)
+        {
+            Vector3 vertexData = vertexMatrix.MultiplyPoint(vertexs[i]);
+            Vector3 vectorData = vectorMatrix.MultiplyVector(vectors[i]);
+            vectorData.Normalize();
+            Gizmos.DrawLine(vertexData, vertexData + vectorData * vectorLen);
+        }
+    }
+}
-- 
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