Qfyilyi

I am trying to create two objects an octagon and a pyramid on the canvas. The octagon is appearing without any problem but the pyramid is not. I am attaching the code of the pyramid.

pyramidPositionBuffer = gl.createBuffer();

gl.bindBuffer(gl.ARRAY_BUFFER, pyramidPositionBuffer);



let pyramidVerts = [

       0.0,  0.5,  0.0, //0

      -0.5,  0.0, -0.5, //1

       0.5,  0.0, -0.5, //2

       0.5,  0.0,  0.5, //3

      -0.5,  0.0,  0.5 //4

      ];



pyramidPositionBuffer.itemSize = 3;

pyramidPositionBuffer.numItems = 5;

gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(pyramidVerts), gl.STATIC_DRAW);



pyramidColorBuffer = gl.createBuffer();

gl.bindBuffer(gl.ARRAY_BUFFER, pyramidColorBuffer);



let pyramidColors = [

        1.0, 1.0, 1.0, 1.0,

        1.0, 0.0, 0.0, 1.0,

        1.0, 1.0, 0.0, 1.0,

        0.0, 1.0, 0.0, 1.0,

        0.0, 0.0, 1.0, 1.0

        ];



pyramidColorBuffer.itemSize = 4;

pyramidColorBuffer.numItems = 5;

gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(pyramidColorBuffer),gl.STATIC_DRAWS);



pyramidIndexBuffer = gl.createBuffer();

gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, pyramidIndexBuffer);



let pyramidIndeces = [

        0, 1, 2,

        0, 2, 3,

        0, 3, 4,

        0, 4, 1

];



pyramidIndexBuffer.itemSize = 1;

pyramidIndexBuffer.numItems = 12;

gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(pyramidIndeces), gl.STATIC_DRAW);



}



function drawScene() {

    gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);



    mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);



    mat4.identity(mvMatrix);



    mat4.translate(mvMatrix, [-1.5, 0.0, -6.5]); // We store a translation to our matrix, so when the first object is drawn it will be in that position.



    // Connect the attributes with the shaders and draw...

    gl.bindBuffer(gl.ARRAY_BUFFER,octagonPositionBuffer);

    gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, octagonPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ARRAY_BUFFER, octagonColorBuffer);

    gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, octagonColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, octagonIndexBuffer);



        setMatrixUniforms();

    gl.drawElements(gl.TRIANGLES, octagonIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);



    mat4.translate(mvMatrix, [2.8, 0.0, 0.0]);

    gl.bindBuffer(gl.ARRAY_BUFFER,pyramidPositionBuffer);

    gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, pyramidPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ARRAY_BUFFER, pyramidColorBuffer);

    gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, pyramidColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, pyramidIndexBuffer);



        setMatrixUniforms();

    gl.drawElements(gl.TRIANGLES, pyramidIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);

}

I created the pyramid with the same way I created the octagon but for some reason it is not appearing. If I try to draw the octagon two times it has no problem.

There are 2 issues in the line

gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(pyramidColorBuffer),gl.STATIC_DRAWS);

STATIC_DRAWS is not a valid enumeration constant, the correct name is STATIC_DRAW. In this case you should get an INVALID_ENUM error.

pyramidColorBuffer is the buffer object (pyramidColorBuffer = gl.createBuffer()), but not the array for the generic vertex attributes data. The name of the array is pyramidColors. In this case you should get an INVALID_OPERATION error.

Change the line to

gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(pyramidColors), gl.STATIC_DRAW);

to solve the issue.

Enable of the generic vertex attribute arrays is missing in your code:

gl.enableVertexAttribArray( shaderProgram.vertexPositionAttribute );

gl.enableVertexAttribArray( shaderProgram.vertexColorAttribute );

But possibly this is only missing in the code snippet which you have posted in your question.