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Perspective - Orthogonal Projection WebGL

user13444
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user13444 Published in July 21, 2018, 11:26 am

I need to complete a task where it is asked to me to build a rotating cube and to add it some functions. I had no problem to rotate , translate and scale it. Then I had to to apply a orthogonal projection and that's ok , it works.

Now the next task is to add a button that switches orthogonal/perspective projection and to use the same slider to che modify near and far plane both in perspective and orthogonal view. I start the program with orthogonal projection and it works , the problem is that if I switch to perspective the field of view is too big and using the slider I can see only a part of the rotating cube.

Probably I'm using not appropriate parameters. Here is the code :

HTML

<!DOCTYPE html>
<html>

<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 -1 <input id="slideX" type="range"
    min="-1" max="1" step="0.1" value="0" />
    1 </div>

<div>Traslation on Y -1 <input id="slideY" type="range"
    min="-1" max="1" step="0.1" value="0" />
    1 </div>

<div>Traslation on Z -1 <input id="slideZ" type="range"
    min="-1" max="1" step="0.1" value="0" />
    1 </div>

<div>Scaling on X -1 <input id="ScalingX" type="range"
    min="0" max="1" step="0.1" value="0" />
    1 </div>
<div>Scaling on Y -1 <input id="ScalingY" type="range"
    min="0" max="1" step="0.1" value="0" />
    1 </div>
<div>Scaling on Z -1 <input id="ScalingZ" type="range"
    min="0" max="1" step="0.1" value="0" />
    1 </div>
<div>
    Ortho Increase
    <input id="depthSlider" type="range"
    min="0.5" max="10" step="0.1" value ="2" />
    Decrease
</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;

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;
    //gl_Position = scaling *rz * ry * rx * traslation * vPosition ;  // ORDINE : scaling -> rotazione -> traslation

    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" width="1024" height="1024">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
</body>
</html>

JS

"use strict";

var canvas;
var gl;

var numVertices  = 36;

var numChecks = 8;

var program;

var c;

var flag = true;

var direction = true;

var rx;
var ry;
var rz;
var traslation_loc;
var tx = 0 ;
var ty = 0;
var tz = 0;
var scaling_loc;
var sx = 1.0;
var sy = 1.0;
var sz = 1.0;

var pointsArray = [];
var colorsArray = [];


//Point 4
var near = -1;
var far = 1;
var radius = 1.0;
var theta  = 0.0;
var phi    = 0.0;
var dr = 5.0 * Math.PI/180.0;

var left = -1.0;
var right = 1.0;
var ytop = 1.0;
var bottom = -1.0;

var mvMatrix, pMatrix;
var modelView, projection;
var eye;

const at = vec3(0.0, 0.0, 0.0);
const up = vec3(0.0, 1.0, 0.0);

var eye = vec3(0.02, 0.02, 0.02);
//

//Point 5
var fovy = 45.0;
var aspect;
var orthoBool = true;
//


var vertices = [
    vec4( -0.5, -0.5,  0.5, 1.0 ),
    vec4( -0.5,  0.5,  0.5, 1.0 ),
    vec4( 0.5,  0.5,  0.5, 1.0 ),
    vec4( 0.5, -0.5,  0.5, 1.0 ),
    vec4( -0.5, -0.5, -0.5, 1.0 ),
    vec4( -0.5,  0.5, -0.5, 1.0 ),
    vec4( 0.5,  0.5, -0.5, 1.0 ),
    vec4( 0.5, -0.5, -0.5, 1.0 )
];

var vertexColors = [
    vec4( 0.0, 0.0, 0.0, 1.0 ),  // black
    vec4( 1.0, 0.0, 0.0, 1.0 ),  // red
    vec4( 1.0, 1.0, 0.0, 1.0 ),  // yellow
    vec4( 0.0, 1.0, 0.0, 1.0 ),  // green
    vec4( 0.0, 0.0, 1.0, 1.0 ),  // blue
    vec4( 1.0, 0.0, 1.0, 1.0 ),  // magenta
    vec4( 0.0, 1.0, 1.0, 1.0 ),  // white
    vec4( 0.0, 1.0, 1.0, 1.0 )   // cyan
];

var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = xAxis;

var theta = [45.0, 45.0, 45.0];

//var thetaLoc;






function quad(a, b, c, d) {
     pointsArray.push(vertices[a]);
     colorsArray.push(vertexColors[a]);

     pointsArray.push(vertices[b]);
     colorsArray.push(vertexColors[a]);

     pointsArray.push(vertices[c]);
     colorsArray.push(vertexColors[a]);

     pointsArray.push(vertices[a]);
     colorsArray.push(vertexColors[a]);

     pointsArray.push(vertices[c]);
     colorsArray.push(vertexColors[a]);

     pointsArray.push(vertices[d]);
     colorsArray.push(vertexColors[a]);
}

function colorCube()
{
    quad( 1, 0, 3, 2 );
    quad( 2, 3, 7, 6 );
    quad( 3, 0, 4, 7 );
    quad( 6, 5, 1, 2 );
    quad( 4, 5, 6, 7 );
    quad( 5, 4, 0, 1 );
}


window.onload = function init() {

    canvas = document.getElementById( "gl-canvas" );

    gl = WebGLUtils.setupWebGL( canvas );
    if ( !gl ) { alert( "WebGL isn't available" ); }

    gl.viewport( 0, 0, canvas.width, canvas.height );

    // Point 5 -> define aspect
    aspect =  canvas.width/canvas.height;


    gl.clearColor( 1.0, 1.0, 1.0, 1.0 );

    gl.enable(gl.DEPTH_TEST);

    //
    //  Load shaders and initialize attribute buffers
    //
    program = initShaders( gl, "vertex-shader", "fragment-shader" );


    gl.useProgram( program );

    colorCube();




    var cBuffer = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
    gl.bufferData( gl.ARRAY_BUFFER, flatten(colorsArray), gl.STATIC_DRAW );

    var vColor = gl.getAttribLocation( program, "vColor" );
    gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
    gl.enableVertexAttribArray( vColor );

    var vBuffer = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer);
    gl.bufferData( gl.ARRAY_BUFFER, flatten(pointsArray), gl.STATIC_DRAW );

    var vPosition = gl.getAttribLocation( program, "vPosition" );
    gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
    gl.enableVertexAttribArray( vPosition );

    // Possiamo commentare quello che riguarda il theta per il punto 2
    //thetaLoc = gl.getUniformLocation(program, "theta");

    // Point 2 - Rotation

    //X AXIS

    rx = gl.getUniformLocation(program, "rx");


    //Y AXIS

    ry = gl.getUniformLocation(program, "ry");



    //Z AXIS

     rz = gl.getUniformLocation(program, "rz");


    // Traslation Matrix

    traslation_loc = gl.getUniformLocation(program , "traslation");

    // Scaling Matrix

    scaling_loc = gl.getUniformLocation(program , "scaling");

    // Projection and Model matrix
    modelView = gl.getUniformLocation( program, "modelView" );
    projection = gl.getUniformLocation( program, "projection" );





    //**************


 document.getElementById("ButtonX").onclick = function(){axis = xAxis;};
 document.getElementById("ButtonY").onclick = function(){axis = yAxis;};
 document.getElementById("ButtonZ").onclick = function(){axis = zAxis;};
 document.getElementById("ButtonT").onclick = function(){flag = !flag;};
 document.getElementById("Direction").onclick = function() { direction = !direction;};
 document.getElementById( "slideX" ).oninput = function(){ tx = parseFloat(event.target.value,10); };
 document.getElementById( "slideY" ).oninput = function(){ ty = parseFloat(event.target.value,10); };
 document.getElementById( "slideZ" ).oninput = function(){ tz = parseFloat(event.target.value,10); };
 document.getElementById( "ScalingX" ).oninput = function(){ sx = parseFloat(event.target.value,10); };
 document.getElementById( "ScalingY" ).oninput = function(){ sy = parseFloat(event.target.value,10); };
 document.getElementById( "ScalingZ" ).oninput = function(){ sz = parseFloat(event.target.value,10); };
 // Point 5
 document.getElementById("OrthoPersp").onclick = function(){orthoBool = !orthoBool;};

 // Point 4

    // per documentazine leggi la parte sotto il codice a pag 244 con spiegazione sul clip out
    // occhio che qua accorcia sia il piano vicino che quello lontano , se commentassi riga 225 o 226 , e accorcerei solo uno


    document.getElementById("depthSlider").onchange = function() {
        far = event.srcElement.value/2;
        near = -event.srcElement.value/2;
    };

    render();
}








var render = function() {
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);


    // Point 4
    //*************************************
    //eye = vec3(radius*Math.sin(phi), radius*Math.sin(theta),
              // radius*Math.cos(phi)); RIMANE COMMENTATO

    //mvMatrix = lookAt(eye, at , up);
    //pMatrix = ortho(left, right, bottom, ytop, near, far);

    //gl.uniformMatrix4fv( modelView, false, flatten(mvMatrix) );
    //gl.uniformMatrix4fv( projection, false, flatten(pMatrix) );


    //*************************************



    //Point 5
    //*************************************
    mvMatrix = lookAt(eye, at , up);

    if (orthoBool) {
        pMatrix = ortho(left, right, bottom, ytop, near, far); }
    else {

        pMatrix=perspective(fovy , aspect , near , far); }

    gl.uniformMatrix4fv( modelView, false, flatten(mvMatrix) );
    gl.uniformMatrix4fv( projection, false, flatten(pMatrix) );


    //*************************************


    // Point 3 -> Scaling

    var scaling = [sx , 0.0 , 0.0 , 0.0,
                   0.0  , sy, 0.0 , 0.0,
                   0.0 , 0.0 , sz , 0.0,
                   0.0 , 0.0 , 0.0 , 1];
    gl.uniformMatrix4fv(scaling_loc,false,scaling);


    // ****************************************
    //X AXIS - Point 2
    var theta_x_degree  = theta[0];
    var theta_x_radians = theta_x_degree * Math.PI / 180;
    var s_x = Math.sin(theta_x_radians);
    var c_x = Math.cos(theta_x_radians);
    var rx_loc = [ 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 ];
    gl.uniformMatrix4fv(rx, false, rx_loc);

    //Y AXIS - Point 2
    var theta_y_degree  = theta[1];
    var theta_y_radians = theta_y_degree * Math.PI / 180;
    var s_y = Math.sin(theta_y_radians);
    var c_y = Math.cos(theta_y_radians);
    var ry_loc = [ 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 ];
    gl.uniformMatrix4fv(ry, false, ry_loc);


    //Z AXIS - Point 2
    var theta_z_degree  = theta[2];
    var theta_z_radians = theta_z_degree * Math.PI / 180;
    var s_z = Math.sin(theta_z_radians);
    var c_z = Math.cos(theta_z_radians);
    var rz_loc = [ 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  ];
    gl.uniformMatrix4fv(rz, false, rz_loc);

    // ****************************************

    // Point 3 -> Traslation

    var traslation = [1.0 , 0.0 , 0.0 , 0.0,
                      0.0 , 1.0 , 0.0 , 0.0,
                      0.0 , 0.0 , 1.0 , 0.0,
                       tx , ty , tz , 1.0];

    gl.uniformMatrix4fv(traslation_loc,false,traslation);


    // ****************************************




    // ****************************************

    // Point 1 --> Change and Toggle Rotation
    if((direction)&&(!flag)) theta[axis] += -2.0;
    if((!direction)&&(!flag)) theta[axis] += +2.0;

    if(!direction) {theta[axis] += -2.0; }
    if(direction) {theta[axis] += 2.0 ; }

    // ****************************************

    //gl.uniform3fv(thetaLoc, theta);
    gl.drawArrays( gl.TRIANGLES, 0, numVertices );
    requestAnimFrame(render);
}
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