纹理平面上的OpenGL Lighting无法正常工作

问题描述 投票:1回答:1

我想点亮纹理平面,但这不起作用。实心球上的光很好,但纹理平面不轻。

Whole Image

实心球上的照明效果很好。

但是,纹理平面上的照明不起作用。 (GL_DECAL,GL_REPLACE;我也试过GL_MODULATE)

这是我的渲染代码的片段。 (Whole code on GitHub

加载纹理。

  sf::Image image;

  if (!image.loadFromFile(path))
    return false;
  glGenTextures(1, &id);
  glBindTexture(GL_TEXTURE_2D, id);

  glTexImage2D(
    GL_TEXTURE_2D, 0, GL_RGBA,
    image.getSize().x, image.getSize().y, 0,
    GL_RGBA, GL_UNSIGNED_BYTE,
    image.getPixelsPtr()
  );

  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

初始化

  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
  glClearDepth(1.0f);
  glEnable(GL_DEPTH_TEST);
  glDepthFunc(GL_LEQUAL);
  glShadeModel(GL_SMOOTH);
  //glEnable(GL_CULL_FACE);
  glFrontFace(GL_CCW);
  glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
  glutSetCursor(GLUT_CURSOR_NONE);
  light.Init();

  camera.SetPin((GLfloat)width / 2, (GLfloat)height/2);

显示回调

  adjustPerspective();

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glEnable(GL_LIGHTING);

  glPushMatrix();
  camera.SetLookAt();
  light.On();

  // TODO: dsiplay processing
  for (auto& obj : display_objs)
  {
    glPushMatrix();
    obj->Draw();
    glPopMatrix();
  }
  glPopMatrix();

  // print fps and swap buffers

光初始化功能

  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
  glEnable(GL_COLOR_MATERIAL);

  // Set lighting intensity and color
  glLightfv(GL_LIGHT0, GL_AMBIENT, qaAmbientLight);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, qaDiffuseLight);
  glLightfv(GL_LIGHT0, GL_POSITION, qaLightPosition);
  glLightfv(GL_LIGHT0, GL_SPECULAR, qaSpecularLight);
  ////////////////////////////////////////////////

  glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 80.0);// set cutoff angle
  glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, dirVector0);
  glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, 10.0); // set focusing strength

Light.On()函数

  glPushMatrix();
  glTranslatef(2.0, 10.0, 2.0);
  //glRotatef(90, 1, 0, 0);
  glLightfv(GL_LIGHT0, GL_POSITION, qaLightPosition);
  glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, dirVector0);
  glPopMatrix();

  glPushMatrix();
  glDisable(GL_LIGHTING);
  glTranslatef(2.0, 0.0, 2.0);
  glRotatef(-90.0, 1.0, 0.0, 0.0);
  glutWireCone(tan(80.0 / 180.0 * 3.14159265),10.0,20,20);
  glEnable(GL_LIGHTING);
  glPopMatrix();

这是纹理平面绘制功能。

  float tile_x = 0.125;

  glTranslatef(x, y, z);

  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glEnable(GL_TEXTURE_2D);
  glBindTexture(GL_TEXTURE_2D, tex.GetId());
  glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

  glBegin(GL_QUADS);
    // Both of the following cases not work.
    glNormal3f(0, -1, 0);
    glNormal3f(0, 1, 0);
    glTexCoord2f(0.0, 0.0); glVertex3f(0, 0, 0);
    glTexCoord2f(height*tile_x, 0.0); glVertex3f(0, 0, width);
    glTexCoord2f(height*tile_x, width*tile_x); glVertex3f(height, 0, width);
    glTexCoord2f(0.0, width*tile_x); glVertex3f(height, 0, 0);
  glEnd();

  glDisable(GL_TEXTURE_2D);
  glDisable(GL_BLEND);

我更改了向量方向,更改了glTexEnvf属性,更改了代码的顺序,但没有修复错误。我认为我的代码存在根本性错误,但我找不到它。为什么会发生这种情况,我该如何解决?

c++ opengl textures lighting opengl-compat
1个回答
3
投票

我想点亮纹理平面,但这不起作用。实心球上的光很好,但纹理平面不轻。

这是由OpenGLs标准灯光模型的Gouraud Shading模型引起的问题。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。

这意味着在您的情况下,计算地面四边形角的光。对如此计算的光进行插值以对其间的所有片段进行插值。在光矢量的角落处的法向矢量的角度倾向于90°。因此,整个地面四边形看起来几乎没有光。

由于每个顶点计算光,因此计算的光比四边形的4个角更多的位置,并且质量增加。请注意,球体上的光看起来几乎是完美的,因为球体围绕其形状包含许多顶点。

尝试以下代码,将四元组拆分为tile:

int   tiles = 5;
float u_max = height*tile_x;
float v_max = width*tile_x

glBegin(GL_QUADS);
glNormal3f(0, 1, 0);

for (int x=0; x < tiles; ++x)
{
    for (int y=0; y < tiles; ++y)
    {
        x0 = (float)x/(float)tiles;
        x1 = (float)(x+1)/(float)tiles;
        y0 = (float)y/(float)tiles;
        y1 = (float)(y+1)/(float)tiles;

        glTexCoord2f(u_max*x0, v_max*y0);  glVertex3f(height*x0, 0, widht*y0);
        glTexCoord2f(u_max*x1, v_max*y0);  glVertex3f(height*x0, 0, widht*y1);
        glTexCoord2f(u_max*x1, v_max*y1);  glVertex3f(height*x1, 0, widht*y1);
        glTexCoord2f(u_max*x0, v_max*y1);  glVertex3f(height*x1, 0, widht*y0);
    }
}
glEnd();

当然,您也可以编写自己的着色器并实现每个片段照明。但是不推荐使用的固定功能管道OpenGL标准光模型不支持每个片段照明。

查看WebGL示例中的差异:

(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.disable(gl.CULL_FACE);
    
    
    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.lightPos", [0.0, 0.0, 0.25] )
    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, -1.5, 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 = [-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 sphere_nv  = [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 sphere_col = [0.8, 0.6, 0.3, 0.8, 0.6, 0.3, 0.8, 0.6, 0.3, 0.8, 0.6, 0.3];
    var sphere_inx = [0, 1, 2, 0, 2, 3];
    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, 2, 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  lightPos;
      vec3  ambient;
      vec3  diffuse;
      vec3  specular;
      float shininess;
  };

  uniform TLightSource u_lightSource;
  
  vec3 Light( vec3 eyeV, vec3 N, vec3 P )
  {
      vec3  lightCol  = u_lightSource.ambient;
      vec3  L         = normalize( u_lightSource.lightPos-P );
      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 ) * sign(vertNV.z);
      vertCol       = inCol * Light( eyeV, normalV, vertPos );
      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  lightPos;
  vec3  ambient;
  vec3  diffuse;
  vec3  specular;
  float shininess;
};

uniform TLightSource u_lightSource;

vec3 Light( vec3 eyeV, vec3 N, vec3 P )
{
  vec3  lightCol  = u_lightSource.ambient;
  vec3  L         = normalize( u_lightSource.lightPos - P );
  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 ) * sign(vertNV.z);
  vec3 color   = vertCol * Light( eyeV, normalV, vertPos );
  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="10"/></td>
</tr></table></form>
<canvas id="canvas" style="border: none;" width="100%" height="100%"></canvas>
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