This is my first experiment in WebGL: I am trying to add a cube, octahedron and tetrahedron to a single canvas. I programmed each shape separately and tested them: they each work when living inside their own canvases. When I tried adding them together, that's when things go wrong. At present I only see the octahedron spinning about (no, it is not obscuring the other shapes, I have checked). When I comment the octahedron out, I see the cube and tetrahedron spinning around, but their colour buffers have been mixed up and are not what I wanted (when I try to separate their colour buffers, nothing renders to the screen). I realise there are inconsistencies in how I coded these, but the present configuration was the only way I could get both those two objects to show. Now the recent addition of the octahedron made the previous two disappear.
I sense the issue relates to vertex and colour buffers, but I don’t have enough experience and background to know what to amend. Do I instantiate a colour buffer for each of these? That would make sense. I tried and this but it did not go well for the first two shapes, hence the mixing of colour buffers.
Would be much appreciated if anyone could advise / help me out on this. Have been spending countless hours trying to get to grips with this problem.
var canvas;
var gl;
var NumVertices = 36;
var points = [];
var colors = [];
var pointsT = [];
var colorsT = [];
var pointsO = [];
var colorsO = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL is not available" ); }
// --------------- Cube --------------------------
colorCube();
// --------------- Tetrahedron -------------------
colorTetra();
// --------------- Octohedron --------------------
colorOcto();
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 0.1, 0.1, 0.1, 1.0 );
gl.enable(gl.DEPTH_TEST);
// --------------- Load shaders and initialize attribute buffers
// --------------- Cube --------------------------
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), 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(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
// --------------- Tetrahedron -------------------
var tcBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, tcBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var tvColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( tvColor, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( tvColor );
var tvBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, tvBuffer);
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var tvPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( tvPosition, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( tvPosition );
// --------------- Octohedron --------------------
var ocBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, ocBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colorsO), gl.STATIC_DRAW );
var ovColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( ovColor, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( ovColor );
var ovBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, ovBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(pointsO), gl.STATIC_DRAW );
var ovPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( ovPosition, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( ovPosition );
render();
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
theta[axis] += 2.0;
gl.uniform3fv(thetaLoc, theta);
// Render cube
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
// Render tetrahedron
gl.drawArrays( gl.TRIANGLES, 0, points.length );
// Render sphere
gl.drawArrays( gl.TRIANGLES, 0, pointsO.length );
requestAnimFrame( render );
}
// DEFINE CUBE
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 );
}
function quad(a, b, c, d)
{
var vertices = [
vec3( -0.25, -0.25, 0.25 ),
vec3( -0.25, 0.25, 0.25 ),
vec3( 0.25, 0.25, 0.25 ),
vec3( 0.25, -0.25, 0.25 ),
vec3( -0.25, -0.25, -0.25 ),
vec3( -0.25, 0.25, -0.25 ),
vec3( 0.25, 0.25, -0.25 ),
vec3( 0.25, -0.25, -0.25 )
];
var vertexColors = [
[ 0.9, 0.9, 0.2, 1.0 ], // oarnge
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ], // green
[ 0.0, 0.0, 1.0, 1.0 ], // blue
[ 1.0, 0.0, 1.0, 1.0 ], // magenta
[ 1.0, 1.0, 1.0, 1.0 ], // white
[ 0.0, 1.0, 1.0, 1.0 ] // cyan
];
// Partion the quad into two triangles in order for
// WebGL to be able to render it.
// vertex color assigned by the index of the vertex
var indices = [ a, b, c, a, c, d ];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
colors.push( vertexColors[indices[i]] );
//for solid colored faces use
//colors.push(vertexColors[a]);
}
}
// DEFINE TETRAHEDRON
function colorTetra(){
var verticesT = [
vec3( 0.0000, 0.0000, -0.3500 ),
vec3( 0.0000, 0.3500, 0.1500 ),
vec3( -0.3500, -0.1500, 0.1500 ),
vec3( 0.3500, -0.1500, 0.1500 )
];
tetra(verticesT[0], verticesT[1], verticesT[2], verticesT[3]);
}
function makeTetra( a, b, c, color )
{
// add colors and vertices for one triangle
var baseColors = [
vec3(0.7, 0.7, 0.9, 1.0),
vec3(0.6, 0.8, 0.9, 1.0),
vec3(0.5, 0.6, 0.9, 1.0),
vec3(1.0, 1.0, 0.2, 1.0)
];
colors.push( baseColors[color] );
points.push( a );
colors.push( baseColors[color] );
points.push( b );
colors.push( baseColors[color] );
points.push( c );
}
function tetra( p, q, r, s )
{
// tetrahedron with each side using
// a different color
makeTetra( p, r, q, 0 );
makeTetra( p, r, s, 1 );
makeTetra( p, q, s, 2 );
makeTetra( q, r, s, 3 );
}
// DEFINE OCTOHEDRON
function colorOcto(){
var verticesO = [
vec3( 0.4000, 0.0000, 0.0000 ),
vec3( 0.0000, 0.0000, 0.0000 ),
vec3( 0.0000, 0.4000, 0.0000 ),
vec3( 0.4000, 0.4000, 0.0000 ),
vec3( 0.2000, 0.2000, 0.3000 ),
vec3( 0.2000, 0.2000, -0.3000 )
];
octo(verticesO[0], verticesO[1], verticesO[2], verticesO[3], verticesO[4], verticesO[5]);
}
function makeOcto( a, b, c, color )
{
// add colors and vertices for one triangle
var baseColors = [
vec3(0.6, 0.6, 0.6, 1.0),
vec3(0.3, 0.4, 0.9, 1.0),
vec3(0.9, 0.9, 0.9, 1.0),
];
colorsO.push( baseColors[color] );
pointsO.push( a );
colorsO.push( baseColors[color] );
pointsO.push( b );
colorsO.push( baseColors[color] );
pointsO.push( c );
}
function octo( a, b, c, d , e, f)
{
// tetrahedron with each side using
// a different color
makeOcto( a, d, e, 0 );
makeOcto( a, b, e, 1 );
makeOcto( b, c, e, 0 );
makeOcto( c, d, e, 1 );
makeOcto( a, d, f, 1 );
makeOcto( a, b, f, 2 );
makeOcto( b, c, f, 1 );
makeOcto( c, d, f, 2 );
}
I uploaded the complete code structure here:
https://gist.github.com/Carla-de-Beer/10ad7c7309fad48d94df
See Question&Answers more detail:
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