法线贴图光照效果因方向而异

Question

我正在尝试使用法线贴图代替顶点法线，但我无法弄清楚哪一步出错了。我想将光线方向转换为切线空间，并从那里进行计算。 首先，我将向量法线和切线转换为视图空间。

vec3 norm_viewsp = mat3(view) * normalize(norm);
vec3 tangent_viewsp = mat3(view) * normalize(tangent);
vec3 bitangent_viewsp = cross(tangent_viewsp, norm_viewsp);

接下来，我构建矩阵，该矩阵应该执行从视图空间到切线空间的转换，并使用它来计算在切线空间中到光源的距离。

mat3 tbn = transpose(mat3(tangent_viewsp, bitangent_viewsp, norm_viewsp));
vec3 light_dir = light_pos - pos.xyz;
vec3 light_dir_viewsp = mat3(view) * light_dir;

v_light_dir_tansp = tbn * light_dir_viewsp;

在片元着色器中，我从法线贴图中采样法线，并将其与光线方向相乘。

vec3 norm = texture(normal_map, v_tex_pos).rgb * 2.0 - 1.0;
float diffuse = dot(normalize(norm), normalize(v_light_dir_tansp));

法线贴图肯定加载正确。

在结果中，左上角太暗，左下角太亮。 我认为问题出在光线方向上，但我找不出错误。

请注意，上述图片中的值介于-1和1之间，这就是为什么例如法线贴图看起来太暗的原因。

完整的着色器代码

编辑：光源位于模型的中心。如果使用顶点法线，则照明效果良好。在视图空间而不是切线空间中进行计算没有任何区别。

- Sogomn

---

这只是将双切线乘以-1。这使得左下角成为暗角。 - Sogomn

Answer 1

首先，您需要计算切空间矩阵，在右手系统中可以这样完成:

vec3 norm_viewsp      = mat3(view) * normalize(norm);
vec3 tangent_viewsp   = mat3(view) * normalize(tangent);
vec3 bitangent_viewsp = cross(norm_viewsp, tangent_viewsp);
mat3 tbn              = mat3(tangent_viewsp, bitangent_viewsp, norm_viewsp));

当然，您需要从切线空间中的法线图中获取法向量以及从视图空间中到光源的向量：

vec3 norm_map_tbn     = normalize(texture(normal_map, v_tex_pos).xyz * 2.0 - 1.0);
vec3 light_dir_viewsp = normalize(mat3(view) * (light_pos - pos.xyz));

接下来有两种可能性。由于法线贴图中的法向量在切线空间中，光矢量也可以转换到切线空间，并且可以在切线空间中进行光计算。为此，需要将光矢量通过逆切线空间矩阵进行转换。逆矩阵可以通过GLSL函数inverse计算，而不能通过transpose计算（参见什么是“矩阵求逆”和“矩阵转置”的区别？）。

vec3 light_dir_tbn    = inverse(tbn) * light_dir_viewsp;
float diffuse         = max(0.0, dot(norm_map_tbn, light_dir_tbn);

但你也可以用另一种方式实现。法线图中的法线向量可以转换到视图空间，并且可以在视图空间进行光照计算。为此，需要通过切线空间矩阵将法线向量进行转换。这样可以避免昂贵的inverse操作。 将法线向量替换为tbn[2](切线空间矩阵的Z轴)，以可视化效果而不受法线贴图影响。

vec3 norm_map_viewsp  = tbn * norm_map_tbn;
float diffuse         = max(0.0, dot(norm_map_viewsp, light_dir_viewsp);

注意，Lambertian漫反射光模型通常是这样计算的：

f_lambertian = max( 0.0, dot(N, L ))

如果光源非常靠近物体，则光向量和面法线向量之间的角度在左上角和右下角之间可能会有很大差异。这将导致亮度不均匀，因为Lambertian漫反射光模型在其角度的余弦线性依赖。
用tbn[2]（切线空间矩阵的Z轴）替换法线向量，以可视化效果而不受法线贴图影响。
注意，必须确保所有法线向量指向相同方向，并且切线指向相同方向。请参见以下示例，演示如果其中一个法线向量被反转会发生什么：

glArrayType = typeof Float32Array !="undefined" ? Float32Array : ( typeof WebGLFloatArray != "undefined" ? WebGLFloatArray : Array );

function IdentityMat44() {
  var m = new glArrayType(16);
  m[0]  = 1; m[1]  = 0; m[2]  = 0; m[3]  = 0;
  m[4]  = 0; m[5]  = 1; m[6]  = 0; m[7]  = 0;
  m[8]  = 0; m[9]  = 0; m[10] = 1; m[11] = 0;
  m[12] = 0; m[13] = 0; m[14] = 0; m[15] = 1;
  return m;
};

function RotateAxis(matA, angRad, axis) {
    var aMap = [ [1, 2], [2, 0], [0, 1] ];
    var a0 = aMap[axis][0], a1 = aMap[axis][1]; 
    var sinAng = Math.sin(angRad), cosAng = Math.cos(angRad);
    var matB = new glArrayType(16);
    for ( var i = 0; i < 16; ++ i ) matB[i] = matA[i];
    for ( var i = 0; i < 3; ++ i ) {
        matB[a0*4+i] = matA[a0*4+i] * cosAng + matA[a1*4+i] * sinAng;
        matB[a1*4+i] = matA[a0*4+i] * -sinAng + matA[a1*4+i] * cosAng;
    }
    return matB;
}

function Cross( a, b ) { return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0], 0.0 ]; }
function Dot( a, b ) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }
function Normalize( v ) {
    var len = Math.sqrt( v[0] * v[0] + v[1] * v[1] + v[2] * v[2] );
    return [ v[0] / len, v[1] / len, v[2] / len ];
}

var Camera = {};
Camera.create = function() {
    this.pos    = [0, 1.5, 0.0];
    this.target = [0, 0, 0];
    this.up     = [0, 0, 1];
    this.fov_y  = 90;
    this.vp     = [800, 600];
    this.near   = 0.5;
    this.far    = 100.0;
}
Camera.Perspective = function() {
    var fn = this.far + this.near;
    var f_n = this.far - this.near;
    var r = this.vp[0] / this.vp[1];
    var t = 1 / Math.tan( Math.PI * this.fov_y / 360 );
    var m = IdentityMat44();
    m[0]  = t/r; m[1]  = 0; m[2]  =  0;                              m[3]  = 0;
    m[4]  = 0;   m[5]  = t; m[6]  =  0;                              m[7]  = 0;
    m[8]  = 0;   m[9]  = 0; m[10] = -fn / f_n;                       m[11] = -1;
    m[12] = 0;   m[13] = 0; m[14] = -2 * this.far * this.near / f_n; m[15] =  0;
    return m;
}
Camera.LookAt = function() {
    var mz = Normalize( [ this.pos[0]-this.target[0], this.pos[1]-this.target[1], this.pos[2]-this.target[2] ] );
    var mx = Normalize( Cross( this.up, mz ) );
    var my = Normalize( Cross( mz, mx ) );
    var tx = Dot( mx, this.pos );
    var ty = Dot( my, this.pos );
    var tz = Dot( [-mz[0], -mz[1], -mz[2]], this.pos ); 
    var m = IdentityMat44();
    m[0]  = mx[0]; m[1]  = my[0]; m[2]  = mz[0]; m[3]  = 0;
    m[4]  = mx[1]; m[5]  = my[1]; m[6]  = mz[1]; m[7]  = 0;
    m[8]  = mx[2]; m[9]  = my[2]; m[10] = mz[2]; m[11] = 0;
    m[12] = tx;    m[13] = ty;    m[14] = tz;    m[15] = 1; 
    return m;
} 

var ShaderProgram = {};
ShaderProgram.Create = function( shaderList ) {
    var shaderObjs = [];
    for ( var i_sh = 0; i_sh < shaderList.length; ++ i_sh ) {
        var shderObj = this.CompileShader( shaderList[i_sh].source, shaderList[i_sh].stage );
        if ( shderObj == 0 )
            return 0;
        shaderObjs.push( shderObj );
    }
    var progObj = this.LinkProgram( shaderObjs )
    if ( progObj != 0 ) {
        progObj.attribIndex = {};
        var noOfAttributes = gl.getProgramParameter( progObj, gl.ACTIVE_ATTRIBUTES );
        for ( var i_n = 0; i_n < noOfAttributes; ++ i_n ) {
            var name = gl.getActiveAttrib( progObj, i_n ).name;
            progObj.attribIndex[name] = gl.getAttribLocation( progObj, name );
        }
        progObj.unifomLocation = {};
        var noOfUniforms = gl.getProgramParameter( progObj, gl.ACTIVE_UNIFORMS );
        for ( var i_n = 0; i_n < noOfUniforms; ++ i_n ) {
            var name = gl.getActiveUniform( progObj, i_n ).name;
            progObj.unifomLocation[name] = gl.getUniformLocation( progObj, name );
        }
    }
    return progObj;
}
ShaderProgram.AttributeIndex = function( progObj, name ) { return progObj.attribIndex[name]; } 
ShaderProgram.UniformLocation = function( progObj, name ) { return progObj.unifomLocation[name]; } 
ShaderProgram.Use = function( progObj ) { gl.useProgram( progObj ); } 
ShaderProgram.SetUniformI1  = function( progObj, name, val ) { if(progObj.unifomLocation[name]) gl.uniform1i( progObj.unifomLocation[name], val ); }
ShaderProgram.SetUniformF1  = function( progObj, name, val ) { if(progObj.unifomLocation[name]) gl.uniform1f( progObj.unifomLocation[name], val ); }
ShaderProgram.SetUniformF2  = function( progObj, name, arr ) { if(progObj.unifomLocation[name]) gl.uniform2fv( progObj.unifomLocation[name], arr ); }
ShaderProgram.SetUniformF3  = function( progObj, name, arr ) { if(progObj.unifomLocation[name]) gl.uniform3fv( progObj.unifomLocation[name], arr ); }
ShaderProgram.SetUniformF4  = function( progObj, name, arr ) { if(progObj.unifomLocation[name]) gl.uniform4fv( progObj.unifomLocation[name], arr ); }
ShaderProgram.SetUniformM33 = function( progObj, name, mat ) { if(progObj.unifomLocation[name]) gl.uniformMatrix3fv( progObj.unifomLocation[name], false, mat ); }
ShaderProgram.SetUniformM44 = function( progObj, name, mat ) { if(progObj.unifomLocation[name]) gl.uniformMatrix4fv( progObj.unifomLocation[name], false, mat ); }
ShaderProgram.CompileShader = function( source, shaderStage ) {
    var shaderScript = document.getElementById(source);
    if (shaderScript) {
      source = "";
      var node = shaderScript.firstChild;
      while (node) {
        if (node.nodeType == 3) source += node.textContent;
        node = node.nextSibling;
      }
    }
    var shaderObj = gl.createShader( shaderStage );
    gl.shaderSource( shaderObj, source );
    gl.compileShader( shaderObj );
    var status = gl.getShaderParameter( shaderObj, gl.COMPILE_STATUS );
    if ( !status ) alert(gl.getShaderInfoLog(shaderObj));
    return status ? shaderObj : 0;
} 
ShaderProgram.LinkProgram = function( shaderObjs ) {
    var prog = gl.createProgram();
    for ( var i_sh = 0; i_sh < shaderObjs.length; ++ i_sh )
        gl.attachShader( prog, shaderObjs[i_sh] );
    gl.linkProgram( prog );
    status = gl.getProgramParameter( prog, gl.LINK_STATUS );
    if ( !status ) alert("Could not initialise shaders");
    gl.useProgram( null );
    return status ? prog : 0;
}

var VertexBuffer = {};
VertexBuffer.Create = function( attributes, indices ) {
    var buffer = {};
    buffer.buf = [];
    buffer.attr = []
    for ( var i = 0; i < attributes.length; ++ i ) {
        buffer.buf.push( gl.createBuffer() );
        buffer.attr.push( { size : attributes[i].attrSize, loc : attributes[i].attrLoc } );
        gl.bindBuffer( gl.ARRAY_BUFFER, buffer.buf[i] );
        gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( attributes[i].data ), gl.STATIC_DRAW );
    }
    buffer.inx = gl.createBuffer();
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, buffer.inx );
    gl.bufferData( gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( indices ), gl.STATIC_DRAW );
    buffer.inxLen = indices.length;
    gl.bindBuffer( gl.ARRAY_BUFFER, null );
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
    return buffer;
}
VertexBuffer.Draw = function( bufObj ) {
  for ( var i = 0; i < bufObj.buf.length; ++ i ) {
        gl.bindBuffer( gl.ARRAY_BUFFER, bufObj.buf[i] );
        gl.vertexAttribPointer( bufObj.attr[i].loc, bufObj.attr[i].size, gl.FLOAT, false, 0, 0 );
        gl.enableVertexAttribArray( bufObj.attr[i].loc );
    }
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufObj.inx );
    gl.drawElements( gl.TRIANGLES, bufObj.inxLen, gl.UNSIGNED_SHORT, 0 );
    for ( var i = 0; i < bufObj.buf.length; ++ i )
       gl.disableVertexAttribArray( bufObj.attr[i].loc );
    gl.bindBuffer( gl.ARRAY_BUFFER, null );
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
}
        
function drawScene(){

    var canvas = document.getElementById( "camera-canvas" );
    Camera.create();
    Camera.vp = [canvas.width, canvas.height];
    var currentTime = Date.now();   
    var deltaMS = currentTime - startTime;

    var texUnit = 0;
    gl.activeTexture( gl.TEXTURE0 + texUnit );
    gl.bindTexture( gl.TEXTURE_2D, textureObj );

    var mapUnit = 1;
    gl.activeTexture( gl.TEXTURE0 + mapUnit );
    gl.bindTexture( gl.TEXTURE_2D, normalMapObj );

    gl.viewport( 0, 0, canvas.width, canvas.height );
    gl.enable( gl.DEPTH_TEST );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
    
    // set up draw shader
    ShaderProgram.Use( progDraw );
    ShaderProgram.SetUniformM44( progDraw, "u_projectionMat44", Camera.Perspective() );
    ShaderProgram.SetUniformM44( progDraw, "u_viewMat44", Camera.LookAt() );
    var modelMat = IdentityMat44()
    modelMat = RotateAxis( modelMat, 105.0 * Math.PI / 180.0, 0 );    
    ShaderProgram.SetUniformM44( progDraw, "u_modelMat44", modelMat );
    ShaderProgram.SetUniformI1( progDraw, "tex", texUnit );
    ShaderProgram.SetUniformI1( progDraw, "normal_map", mapUnit );
    
    // draw scene
    var chg_tang = document.getElementById( "change_tangent" ).checked;
    if ( chg_tang )
      VertexBuffer.Draw( bufPlane2 );
    else
      VertexBuffer.Draw( bufPlane );
}

var Texture = {};
Texture.HandleLoadedTexture2D = function( image, texture, flipY ) {
    gl.activeTexture( gl.TEXTURE0 );
    gl.bindTexture( gl.TEXTURE_2D, texture );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image );
    if ( flipY != undefined && flipY == true )
      gl.pixelStorei( gl.UNPACK_FLIP_Y_WEBGL, true );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT );
   gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT );
    gl.bindTexture( gl.TEXTURE_2D, null );
    return texture;
}
Texture.LoadTexture2D = function( name ) {
    var texture = gl.createTexture();
    texture.image = new Image();
    texture.image.setAttribute('crossorigin', 'anonymous');
    texture.image.onload = function () {
        Texture.HandleLoadedTexture2D( texture.image, texture, true )
    }
    texture.image.src = name;
    return texture;
}

var gl;
var progDraw;
var bufCube = {};
var bufTorus = {};
function sceneStart() {

    var canvas = document.getElementById( "camera-canvas");
    var vp = [canvas.width, canvas.height];
    gl = canvas.getContext( "experimental-webgl" );
    if ( !gl )
      return;

    progDraw = ShaderProgram.Create( 
      [ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );
    progDraw.inPos = gl.getAttribLocation( progDraw, "pos" );
    progDraw.inNV  = gl.getAttribLocation( progDraw, "norm" );
    progDraw.inTV  = gl.getAttribLocation( progDraw, "tangent" );
    progDraw.inTex = gl.getAttribLocation( progDraw, "tex_pos" );
    if ( progDraw == 0 )
        return;

    var planPosData = [-1.0, -1.0, 0.0,     1.0, -1.0, 0.0,     1.0,  1.0,  0.0,    -1.0, 1.0, 0.0];
    var planNVData  = [ 0.0,  0.0, 1.0,     0.0,  0.0, 1.0,     0.0,  0.0,  1.0,     0.0, 0.0, 1.0];
    var planTVData  = [ 1.0,  0.0, 0.0,     1.0,  0.0, 0.0,     1.0,  0.0,  0.0,     1.0, 0.0, 0.0];
    var planTexData = [ 0.0,  0.0,          0.0,  1.0,          1.0,  1.0,           1.0, 0.0     ];
    var planInxData = [0,1,2,0,2,3];
    bufPlane = VertexBuffer.Create(
    [ { data : planPosData, attrSize : 3, attrLoc : progDraw.inPos },
      { data : planNVData,  attrSize : 3, attrLoc : progDraw.inNV },
      { data : planTVData,  attrSize : 3, attrLoc : progDraw.inTV },
      { data : planTexData, attrSize : 2, attrLoc : progDraw.inTex } ],
      planInxData );

    var planPosData2 = [-1.0, -1.0, 0.0,     1.0, -1.0, 0.0,     1.0,  1.0,  0.0,    -1.0, 1.0, 0.0];
    var planNVData2  = [ 0.0,  0.0, 1.0,     0.0,  0.0, 1.0,     0.0,  0.0,  -1.0,     0.0, 0.0, 1.0];
    //var planTVData2  = [ 1.0,  0.0, 0.0,     1.0,  0.0, 0.0,     1.0,  0.0,  0.0,     1.0, 0.0, 0.0];
    var planTVData2  = [ 1.0,  0.0, 0.0,     1.0,  0.0, 0.0,     1.0,  0.0,  0.0,     1.0, 0.0, 0.0];
    var planTexData2 = [ 0.0,  0.0,          0.0,  1.0,          1.0,  1.0,           1.0, 0.0     ];
    var planInxData2 = [0,1,2,0,2,3];
    bufPlane2 = VertexBuffer.Create(
    [ { data : planPosData2, attrSize : 3, attrLoc : progDraw.inPos },
      { data : planNVData2,  attrSize : 3, attrLoc : progDraw.inNV },
      { data : planTVData2,  attrSize : 3, attrLoc : progDraw.inTV },
      { data : planTexData2, attrSize : 2, attrLoc : progDraw.inTex } ],
      planInxData2 );  

    textureObj = Texture.LoadTexture2D( "https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/Gominolas.png" );
    normalMapObj = Texture.LoadTexture2D( "https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/GominolasBump.png" );  

    startTime = Date.now();
    setInterval(drawScene, 50);
}

<script id="draw-shader-vs" type="x-shader/x-vertex">
precision mediump float;

attribute vec4 pos;
attribute vec3 norm;
attribute vec3 tangent;
attribute vec2 tex_pos;

varying vec2 v_tex_pos;
varying vec3 v_light_dir_tansp;

// ADDED -----
varying vec3 v_tangent_vsp;
varying vec3 v_binoraml_vsp;
varying vec3 v_norm_vsp;
// ADDED -----

//uniform mat4 view;
//uniform mat4 view_projection;
// ADDED -----
uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;
// ADDED -----

//const vec3 light_pos = vec3(50.0, 25.0, 50.0);

// ADDED -----
const vec3 light_pos = vec3(0.0, 0.0, 0.25);
// ADDED -----

// ADDED -----
mat3 transpose(mat3 m)
{
    mat3 tm = m;
    for(int i = 0; i < 3; ++i)
    {
       for(int j = 0; j < 3; ++j)
           tm[j][i]=m[i][j];
    }
    return tm;
}
// ADDED -----

void main() {
    // ADDED -----
    mat4 view = u_viewMat44 * u_modelMat44; 
    mat4 view_projection = u_projectionMat44 * view;
    // ADDED -----

 vec3 norm_viewsp = mat3(view) * normalize(norm);
 vec3 tangent_viewsp = mat3(view) * normalize(tangent);
 vec3 bitangent_viewsp = cross(tangent_viewsp, norm_viewsp);
 mat3 tbn = transpose(mat3(tangent_viewsp, bitangent_viewsp, norm_viewsp));
 vec3 light_dir = light_pos - pos.xyz;
 vec3 light_dir_viewsp = mat3(view) * light_dir;
 
 v_tex_pos = tex_pos;
 v_light_dir_tansp = tbn * light_dir_viewsp;
 
 gl_Position = view_projection * pos;

    // ADDED -----
    v_tangent_vsp = tangent_viewsp;
    v_binoraml_vsp = bitangent_viewsp;
    v_norm_vsp = norm_viewsp;
    // ADDED -----
}
</script>

<script id="draw-shader-fs" type="x-shader/x-fragment">
precision mediump float;

varying vec2 v_tex_pos;
varying vec3 v_light_dir_tansp;

// ADDED -----
varying vec3 v_tangent_vsp;
varying vec3 v_binoraml_vsp;
varying vec3 v_norm_vsp;
// ADDED -----

uniform sampler2D tex;
uniform sampler2D normal_map;

void main() {
 vec3 norm = texture2D(normal_map, v_tex_pos).rgb * 2.0 - 1.0;
 float diffuse = dot(normalize(norm), normalize(v_light_dir_tansp));
 diffuse = clamp(diffuse, 0.0, 1.0);

    gl_FragColor = texture2D(tex, v_tex_pos) * diffuse;
 
    // ADDED -----
 vec4 texColor = texture2D(tex, v_tex_pos);
    gl_FragColor = vec4( texColor.rgb * diffuse * 2.0, 1.0 );
    //gl_FragColor = vec4(abs(v_tangent_vsp), 1.0);
    //gl_FragColor = vec4(abs(v_binoraml_vsp), 1.0);
    //gl_FragColor = vec4(abs(v_norm_vsp), 1.0);
    //gl_FragColor = vec4(texture2D(tex, v_tex_pos).rgb, 1.0);
    //gl_FragColor = vec4(texture2D(normal_map, v_tex_pos).rgb, 1.0);
    // ADDED -----
}
</script>

<body onload="sceneStart();">
    <div style="margin-left: 520px;">
        <div style="float: right; width: 100%; background-color: #CCF;">
            <form name="inputs">
                <table>
                    <tr> <td> change tangent </td>
                        <td> <input type="checkbox" id="change_tangent"/>  
                    </td> </tr>
                </table>
            </form>
        </div>
        <div style="float: right; width: 520px; margin-left: -520px;">
            <canvas id="camera-canvas" style="border: none;" width="512" height="512"></canvas>
        </div>
        <div style="clear: both;"></div>
    </div>
</body>

- Rabbid76

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由于法线和切线是正交的，所以转置矩阵应该与逆矩阵相同。我仍然得到了更暗和更亮的角落。 - Sogomn

这就是为什么我感到如此困惑。我只是找不到问题，一切似乎都是正确的。这些是视图空间中的法线、切线和副切线：https://imgur.com/a/YFt1k。看起来它们是垂直的，所以矩阵也应该是正确的。如果我在视图空间而不是切线空间进行计算，结果也是相同的。谢谢你帮我解决这个问题！ - Sogomn

让我们在聊天中继续这个讨论。点击此处进入聊天室。 - Sogomn

但是这与我遵循的任何指南都不一样。为什么一侧如此暗淡，而另一侧如此明亮？即使我改变灯光的高度也没有任何区别。 - Sogomn

是的，它是。该对象在x和z方向上有100个单位，而光源位于50 x和50 z。 - Sogomn

Answer 2

我认为没有必要使用矩阵巫术：

v_light_dir_tansp = vec3(
  dot(tangent_viewsp, light_dir_viewsp),
  dot(bitangent_viewsp, light_dir_viewsp),
  dot(norm_viewsp, light_dir_viewsp)
);

顺便提一下，你的v_light_dir_tansp由于被插值而不准确。

- game development germ

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这正是矩阵乘法的工作原理。在片段着色器中计算光线方向也没有任何区别。 - Sogomn

矩阵和向量的乘积不过是计算点积，但代码更简洁。 - Rabbid76