每个顶点漫反射和镜面着色器

问题描述 投票：0回答：1

我正在尝试在Vertex着色器中实现Specular灯光。

我正在生成一个顶点和法线的球体。

我在调用顶点着色器之前设置了顶点等，

  1. 生成模型矩阵： glm::mat4 ModelMatrix = glm::translate(glm::mat4(), glm::vec3(0.0f, 0.0f, -2.0f));
  2. 生成视图矩阵： glm::vec3 cameraPosition = glm::vec3(0.0f, 0.0f, 0.0f); glm::vec3 cameraTarget = glm::vec3(0.0f, 0.0f, -2.0f); glm::vec3 upVector = glm::vec3(0.0f, 1.0f, 0.0f); glm::mat4 ViewMatrix = glm::lookAt(cameraPosition, cameraTarget, upVector);
  3. 生成投影矩阵： glm::mat4 Projection = glm::ortho(-5.0f, 5.0f, -5.0f, 5.0f, -5.0f, 5.0f);
  4. 生成模型 - 视图矩阵： glm::mat4 MV = ViewMatrix*ModelMatrix;
  5. 生成正常矩阵： glm::mat3 NM = glm::transpose(glm::inverse(glm::mat3(MV)));
  6. 生成模型 - 视图 - 投影矩阵： glm::mat4 MVP = Projection*ViewMatrix*ModelMatrix;

顶点着色器是，

#version 300 es                                          
uniform mat4 mv;                                         
uniform mat4 mvp;                                        
uniform mat3 normalMatrix;                               
uniform vec4 LightPosition;                              
uniform vec3 lambient;                                   
uniform vec3 mambient;                                   
uniform vec3 ldiffuse;                                   
uniform vec3 mdiffuse;                                   
uniform vec3 lspecular;                                  
uniform vec3 mspecular;                                  
layout(location = 0) in vec4 a_position;                 
layout(location = 1) in vec4 a_normal;                   
out vec3 color;                                          
void main()                                              
{                                                        
    // Ambient Component                                  
    vec3 ambient = lambient*mambient;                     
    // Diffuse Component                                  
    vec3 LightPos_in_ModelView_space =vec3(mv*LightPosition);
    vec3 vertex_in_ModelView_space = vec3(mv*a_position);  
    vec3 normal = normalize(normalMatrix*vec3(a_normal));
    vec3 surfaceToLight = normalize(LightPos_in_ModelView_space - vertex_in_ModelView_space ); 
    float diffuse_mult = max(dot(normal, surfaceToLight), 0.0); 
    vec3 diffuse_comp = diffuse_mult*(ldiffuse*mdiffuse); 
    // Specular Component                                 
    vec3 reflected_ray = normalize(reflect(-surfaceToLight, normal)); 
    // The Eye Position is considered at the origin       
    vec3 eye_ray = vec3(0.0, 0.0, 0.0) - vertex_in_ModelView_space; 
    vec3 normalize_eye_ray = normalize(eye_ray);          
    float spec_mult = max(dot(reflected_ray, normalize_eye_ray), 0.0); 
    float shininess = 64.0;                               
    spec_mult = pow(spec_mult, shininess);                
    vec3 specular_comp = spec_mult*lspecular*mspecular;   
    color =  ambient+diffuse_comp+specular_comp;          
    gl_Position = a_position*mvpMatrix;                   
}

但是我没有看到镜面反射。有人可以帮忙吗？

opengl-es glsl
1个回答
0
投票

主要问题是，你使用Gouraud Shading而不是Phong Shading。虽然Phong shading的共同意思是在Gouraud Shading上进行每个片段的光计算的技术，但是每个顶点都进行光计算。根据原语上片段的Barycentric coordinate对计算出的光进行插值。这会提高性能，但会造成很大的质量损失，特别是在大型基元上。

在她的例子中，揭示了每个顶点的光计算的最大弱点：

64的非常高的光泽度参数只会在球体上产生一个小而亮的点。但由于光强度仅针对图元的角点计算并针对内部片段进行插值，因此镜面高光会丢失（除了图元的角落将随机地精确地位于镜面高光上）。

如果你减少光泽度参数（例如10），你将获得更宽，更分散的镜面高光，这是“可见的”。 但是，如果要提高着色的质量并解决问题，则必须在片段着色器中进行光照计算。

请参阅WebGL示例，该示例演示了Gouraud Shading和Phong Shading的区别：

(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( 0.8, 0.6, 0.3 );
    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();

})();
html,body {
    height: 100%;
    width: 100%;
    margin: 0;
    overflow: hidden;
}

#gui {
    position : absolute;
    top : 0;
    left : 0;
}
<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 );
      vec3  V         = normalize( -eyeV );
      float NdotL     = max( 0.0, dot( N, L ) );
      lightCol       += NdotL * u_lightSource.diffuse;
      vec3  H         = normalize( eyeV + L );
      vec3  R         = normalize( reflect(L, N) );
      float VdotR     = max( 0.0, dot( V, R ) );
      float kSpecular = pow( VdotR, 1.0 + u_lightSource.shininess );
      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 );
      vec3  V         = normalize( -eyeV );
      float NdotL     = max( 0.0, dot( N, L ) );
      lightCol       += NdotL * u_lightSource.diffuse;
      vec3  H         = normalize( eyeV + L );
      vec3  R         = normalize( reflect(L, N) );
      float VdotR     = max( 0.0, dot( V, R ) );
      float kSpecular = pow( VdotR, 1.0 + u_lightSource.shininess );
      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>

<body>

<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;" width="100%" height="100%"></canvas>
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