Phong 和 Gouraud 着色 WebGL
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【中文标题】Phong 和 Gouraud 着色 WebGL【英文标题】：Phong and Gouraud Shading WebGL 【发布时间】：2018-04-22 13:08:29 【问题描述】：我在 Gouraud 着色中读到，片段的颜色是在顶点着色器中计算的。而在 Phong Shading 中，片段的颜色是在片段着色器中计算的。
在这个实现中，我们使用了哪些？
我不明白它们之间的确切区别。 谁能帮助我？谢谢
<button id = "ButtonX">Rotate X</button>
<button id = "ButtonY">Rotate Y</button>
<button id = "ButtonZ">Rotate Z</button>
<button id = "ButtonT">Toggle Rotation</button>
<button id="Direction">Change Direction</button>
<button id="OrthoPersp">Change Ortho/Persp</button>
<div>Traslation on X <input id="slideX" type="range"
min="-1" max="1" step="0.1" value="0" />
</div>
<div>Traslation on Y <input id="slideY" type="range"
min="-1" max="1" step="0.1" value="0" />
</div>
<div>Traslation on Z <input id="slideZ" type="range"
min="-1" max="1" step="0.1" value="0" />
</div>
<div>Scaling on X <input id="ScalingX" type="range"
min="0" max="1" step="0.1" value="0" />
</div>
<div>Scaling on Y <input id="ScalingY" type="range"
min="0" max="1" step="0.1" value="0" />
</div>
<div>Scaling on Z <input id="ScalingZ" type="range"
min="0" max="1" step="0.1" value="0" />
</div>
<div>
zNear Min<input id="zNearSlider" type="range" min="0.00" max="2.8" step="0.1" value="0.3">
Max
</div>
<div>
zFar Min<input id="zFarSlider" type="range" min="3" max="10" step="3.0" value="3">
Max
</div>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
//uniform vec3 theta;
// Point 2 -> Move the matrices
// Per spostare le matrici le abbiamo dovuto dichiarare nel file GLSL come uniform
// le matrici rx ry e rz sono rispettivamente le matrici di rotazione sugli assi
uniform mat4 rx;
uniform mat4 ry;
uniform mat4 rz;
// Points 3 -> Traslation Matrix
uniform mat4 traslation;
// Points 3 -> Scaling Matrix
uniform mat4 scaling;
//Point 4 -> MV and P matrices
uniform mat4 modelView;
uniform mat4 projection;
//Poinit 6 -> Light Source
attribute vec4 vNormal;
uniform vec4 ambientProduct, diffuseProduct, specularProduct;
uniform vec4 lightPosition;
uniform float shininess;
void main()
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
//vec3 angles = radians( theta );
//vec3 c = cos( angles );
//vec3 s = sin( angles );
// Remember: the matrices are column-major
/*
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
*/
//fColor = vColor;
// ORDINE : scaling -> rotazione -> traslation
//gl_Position = projection*modelView*scaling *rz * ry * rx * traslation *vPosition ;
//gl_Position.z = -gl_Position.z;
//Point 6
vec3 pos = -(modelView * vPosition).xyz;
vec3 light = lightPosition.xyz;
vec3 L = normalize( light - pos );
vec3 E = normalize( -pos );
vec3 H = normalize( L + E );
vec3 N = normalize( (modelView*vNormal).xyz);
vec4 ambient = ambientProduct;
float Kd = max( dot(L, N), 0.0 );
vec4 diffuse = Kd*diffuseProduct;
float Ks = pow( max(dot(N, H), 0.0), shininess );
vec4 specular = Ks * specularProduct;
if( dot(L, N) < 0.0 )
specular = vec4(0.0, 0.0, 0.0, 1.0);
fColor = ambient + diffuse + specular;
fColor.a = 1.0;
gl_Position = projection*modelView*scaling *rz * ry * rx * traslation *vPosition ;
gl_Position.z = -gl_Position.z;
// *******************
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
gl_FragColor = fColor;
</script>
<script type="text/javascript" src="../Common/webgl-utils.js"></script>
<script type="text/javascript" src="../Common/initShaders.js"></script>
<script type="text/javascript" src="../Common/MV.js"></script>
<script type="text/javascript" src="Homework1.js"></script>
<body>
<canvas id="gl-canvas" >
Oops ... your browser doesn't support the html5 canvas element
</canvas>
</body>
</html>
【问题讨论】：
【参考方案1】：我不明白它们之间的确切区别。谁能帮助我？
问题代码sn-p中使用的技术是Gouraud Shading。
通常Phong shading 表示该技术，它对每个片段进行光计算，相比之下Gouraud Shading，光计算是按顶点完成的。
这意味着在Phong shading 处，光照计算是在片段着色器中完成的（不要与Phong reflection model 混淆）。
Phong 底纹：
在Gouraud Shading，光照计算在顶点着色器中完成，用于图元的角（三角形的角）。根据Barycentric coordinate，计算的光（以透视正确方式或线性方式）为基元覆盖的所有片段进行插值。这会提高性能，但会大大降低质量，尤其是在大型基元和强镜面高光上。
Gouraud 着色：
请注意，光线在表面上不是线性分布的。如果仅针对某些样本计算光并在它们之间进行插值，则会导致平面污点。
查看示例，比较两种技术：
(function loadscene()
var resize, gl, gouraudDraw, phongDraw, vp_size;
var bufSphere = ;
function render(delteMS)
var shading = document.getElementById( "shading" ).value;
var shininess = document.getElementById( "shininess" ).value;
var ambientCol = [0.2, 0.2, 0.2];
var diffuseCol = [0.6, 0.6, 0.6];
var specularCol = [0.8, 0.8, 0.8];
Camera.create();
Camera.vp = vp_size;
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 );
gl.enable(gl.CULL_FACE);
gl.cullFace(gl.BACK);
//gl.frontFace(gl.CW);
gl.frontFace(gl.CCW);
var progDraw = shading == 0 ? gouraudDraw : phongDraw;;
// set up draw shader
ShaderProgram.Use( progDraw.prog );
ShaderProgram.SetUniformM44( progDraw.prog, "u_projectionMat44", Camera.Perspective() );
ShaderProgram.SetUniformM44( progDraw.prog, "u_viewMat44", Camera.LookAt() );
ShaderProgram.SetUniformF3( progDraw.prog, "u_lightSource.lightDir", [-1.0, -0.5, -2.0] )
ShaderProgram.SetUniformF3( progDraw.prog, "u_lightSource.ambient", ambientCol )
ShaderProgram.SetUniformF3( progDraw.prog, "u_lightSource.diffuse", diffuseCol )
ShaderProgram.SetUniformF3( progDraw.prog, "u_lightSource.specular", specularCol )
ShaderProgram.SetUniformF1( progDraw.prog, "u_lightSource.shininess", shininess )
var modelMat = IdentityMat44()
modelMat = RotateAxis( modelMat, CalcAng( delteMS, 13.0 ), 0 );
modelMat = RotateAxis( modelMat, CalcAng( delteMS, 17.0 ), 1 );
ShaderProgram.SetUniformM44( progDraw.prog, "u_modelMat44", modelMat );
// draw scene
VertexBuffer.Draw( bufSphere );
requestAnimationFrame(render);
function resize()
//vp_size = [gl.drawingBufferWidth, gl.drawingBufferHeight];
vp_size = [window.innerWidth, window.innerHeight]
canvas.width = vp_size[0];
canvas.height = vp_size[1];
gl.viewport( 0, 0, vp_size[0], vp_size[1] );
function initScene()
canvas = document.getElementById( "canvas");
gl = canvas.getContext( "experimental-webgl" );
if ( !gl )
return null;
gouraudDraw =
gouraudDraw.prog = ShaderProgram.Create(
[ source : "gouraud-shader-vs", stage : gl.VERTEX_SHADER ,
source : "gouraud-shader-fs", stage : gl.FRAGMENT_SHADER
],
[ "u_projectionMat44", "u_viewMat44", "u_modelMat44",
"u_lightSource.lightDir", "u_lightSource.ambient", "u_lightSource.diffuse", "u_lightSource.specular", "u_lightSource.shininess", ] );
if ( gouraudDraw.prog == 0 )
return;
gouraudDraw.inPos = gl.getAttribLocation( gouraudDraw.prog, "inPos" );
gouraudDraw.inNV = gl.getAttribLocation( gouraudDraw.prog, "inNV" );
gouraudDraw.inCol = gl.getAttribLocation( gouraudDraw.prog, "inCol" );
phongDraw =
phongDraw.prog = ShaderProgram.Create(
[ source : "phong-shader-vs", stage : gl.VERTEX_SHADER ,
source : "phong-shader-fs", stage : gl.FRAGMENT_SHADER
],
[ "u_projectionMat44", "u_viewMat44", "u_modelMat44",
"u_lightSource.lightDir", "u_lightSource.ambient", "u_lightSource.diffuse", "u_lightSource.specular", "u_lightSource.shininess", ] );
if ( phongDraw.prog == 0 )
return;
phongDraw.inPos = gl.getAttribLocation( phongDraw.prog, "inPos" );
phongDraw.inNV = gl.getAttribLocation( phongDraw.prog, "inNV" );
phongDraw.inCol = gl.getAttribLocation( phongDraw.prog, "inCol" );
// create cube
var layer_size = 16, circum_size = 32;
var rad_circum = 1.0;
var rad_tube = 0.5;
var sphere_pts = [];
var sphere_nv = [];
var sphere_col = [];
sphere_pts.push( 0.0, 0.0, -2.0 );
sphere_nv.push( 0.0, 0.0, -1.0 );
sphere_col.push( 0.8, 0.6, 0.3 );
for ( var i_l = 1; i_l < layer_size; ++ i_l )
var angH = (1.0 - i_l / layer_size) * Math.PI;
var h = Math.cos( angH );
var r = Math.sin( angH );
for ( var i_c = 0; i_c < circum_size; ++ i_c )
var circumX = Math.cos(2 * Math.PI * i_c / circum_size);
var circumY = Math.sin(2 * Math.PI * i_c / circum_size);
sphere_pts.push( r * circumX * 2.0, r * circumY * 2.0, h * 2.0 );
sphere_nv.push( r * circumX, r * circumY, h );
sphere_col.push( 0.8, 0.6, 0.3 );
sphere_pts.push( 0.0, 0.0, 2.0 );
sphere_nv.push( 0.0, 0.0, 1.0 );
sphere_col.push( 0.75, 0.75, 0.75 );
var sphere_inx = [];
for ( var i_c = 0; i_c < circum_size; ++ i_c )
sphere_inx.push( i_c+1, 0, (i_c+1) % circum_size + 1 )
for ( var i_l = 0; i_l < layer_size-2; ++ i_l )
var l1 = i_l * circum_size + 1;
var l2 = (i_l+1) * circum_size + 1
for ( var i_c = 0; i_c < circum_size; ++ i_c )
var i_n = (i_c+1) % circum_size;
sphere_inx.push( l1+i_c, l1+i_n, l2+i_c, l1+i_n, l2+i_n, l2+i_c );
for ( var i_c = 0; i_c < circum_size; ++ i_c )
var i_start = 1 + (layer_size-2) * circum_size;
var i_n = (i_c+1) % circum_size;
sphere_inx.push( i_start + i_c, i_start + i_n, sphere_pts.length/3-1 );
bufSphere = VertexBuffer.Create(
[ data : sphere_pts, attrSize : 3, attrLoc : gouraudDraw.inPos ,
data : sphere_nv, attrSize : 3, attrLoc : gouraudDraw.inNV ,
data : sphere_col, attrSize : 3, attrLoc : gouraudDraw.inCol ],
sphere_inx );
window.onresize = resize;
resize();
requestAnimationFrame(render);
function Fract( val )
return val - Math.trunc( val );
function CalcAng( deltaTime, intervall )
return Fract( deltaTime / (1000*intervall) ) * 2.0 * Math.PI;
function CalcMove( deltaTime, intervall, range )
var pos = self.Fract( deltaTime / (1000*intervall) ) * 2.0
var pos = pos < 1.0 ? pos : (2.0-pos)
return range[0] + (range[1] - range[0]) * pos;
function EllipticalPosition( a, b, angRag )
var a_b = a * a - b * b
var ea = (a_b <= 0) ? 0 : Math.sqrt( a_b );
var eb = (a_b >= 0) ? 0 : Math.sqrt( -a_b );
return [ a * Math.sin( angRag ) - ea, b * Math.cos( angRag ) - eb, 0 ];
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, 3, 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 = shaderScript.text;
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 : null;
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 : null;
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 );
initScene();
)();<style>
html,body
height: 100%;
width: 100%;
margin: 0;
overflow: hidden;
#gui
position : absolute;
top : 0;
left : 0;
</style><script id="gouraud-shader-vs" type="x-shader/x-vertex">
precision mediump float;
attribute vec3 inPos;
attribute vec3 inNV;
attribute vec3 inCol;
varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;
struct TLightSource
vec3 lightDir;
vec3 ambient;
vec3 diffuse;
vec3 specular;
float shininess;
;
uniform TLightSource u_lightSource;
vec3 Light( vec3 eyeV, vec3 N )
vec3 lightCol = u_lightSource.ambient;
vec3 L = normalize( -u_lightSource.lightDir );
float NdotL = max( 0.0, dot( N, L ) );
lightCol += NdotL * u_lightSource.diffuse;
vec3 H = normalize( eyeV + L );
float NdotH = max( 0.0, dot( N, H ) );
float kSpecular = ( u_lightSource.shininess + 2.0 ) * pow( NdotH, u_lightSource.shininess ) / ( 2.0 * 3.14159265 );
lightCol += kSpecular * u_lightSource.specular;
return lightCol;
void main()
vec3 modelNV = mat3( u_modelMat44 ) * normalize( inNV );
vertNV = mat3( u_viewMat44 ) * modelNV;
vec4 modelPos = u_modelMat44 * vec4( inPos, 1.0 );
vec4 viewPos = u_viewMat44 * modelPos;
vertPos = viewPos.xyz / viewPos.w;
vec3 eyeV = normalize( -vertPos );
vec3 normalV = normalize( vertNV );
vertCol = inCol * Light( eyeV, normalV );
gl_Position = u_projectionMat44 * viewPos;
</script>
<script id="gouraud-shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
void main()
gl_FragColor = vec4( vertCol, 1.0 );
</script>
<script id="phong-shader-vs" type="x-shader/x-vertex">
precision mediump float;
attribute vec3 inPos;
attribute vec3 inNV;
attribute vec3 inCol;
varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;
void main()
vec3 modelNV = mat3( u_modelMat44 ) * normalize( inNV );
vertNV = mat3( u_viewMat44 ) * modelNV;
vertCol = inCol;
vec4 modelPos = u_modelMat44 * vec4( inPos, 1.0 );
vec4 viewPos = u_viewMat44 * modelPos;
vertPos = viewPos.xyz / viewPos.w;
gl_Position = u_projectionMat44 * viewPos;
</script>
<script id="phong-shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
struct TLightSource
vec3 lightDir;
vec3 ambient;
vec3 diffuse;
vec3 specular;
float shininess;
;
uniform TLightSource u_lightSource;
vec3 Light( vec3 eyeV, vec3 N )
vec3 lightCol = u_lightSource.ambient;
vec3 L = normalize( -u_lightSource.lightDir );
float NdotL = max( 0.0, dot( N, L ) );
lightCol += NdotL * u_lightSource.diffuse;
vec3 H = normalize( eyeV + L );
float NdotH = max( 0.0, dot( N, H ) );
float kSpecular = ( u_lightSource.shininess + 2.0 ) * pow( NdotH, u_lightSource.shininess ) / ( 2.0 * 3.14159265 );
lightCol += kSpecular * u_lightSource.specular;
return lightCol;
void main()
vec3 eyeV = normalize( -vertPos );
vec3 normalV = normalize( vertNV );
vec3 color = vertCol * Light( eyeV, normalV );
gl_FragColor = vec4( color, 1.0 );
</script>
<form id="gui" name="inputs"><table><tr>
<td><font color= #CCF>Shading:</font></td>
<td><select id="shading">>
<option value="0">Gouraud</option>
<option value="1">Phong</option>
</select></td>
</tr><tr>
<td><font color= #CCF>Shininess:</font></td>
<td><input type="range" id="shininess" min="0" max="100" value="20"/></td>
</tr></table></form>
<canvas id="canvas" style="border: none;" ></canvas>【讨论】：
您链接到的文章说 gouraud 着色在顶点之间使用线性插值，但问题中的代码没有使用线性插值，而是使用透视插值。您必须在顶点着色器中将 gl_Position 除以 w 才能获得线性插值 @gman。你是对的。但关键是，在 gouraud 着色中，光是针对顶点计算的，而不是针对片段进行插值的。 我所做的只是按照您发布的文章进行。如果那篇文章是正确的，那么 gouraud 着色不仅仅是在像素之间进行插值。它以特定的方式进行插值。这种方式不是上面的代码插入和will get different results的方式。 @Rabbid76 感谢您的帮助！因此，如果我想在问题中发布的代码中从 Gouraud 着色切换到 Phong 着色（复制类似于您发布的示例），我必须在片段着色器中移动光的计算，对吗？ @Rabbid76 我做到了，不幸的是，当我切换阴影时，第一个（Gouraud）工作正常，而 Phong 阴影显示我的立方体都是相同的颜色（紫色）以上是关于Phong 和 Gouraud 着色 WebGL的主要内容，如果未能解决你的问题，请参考以下文章