使用 GL.points 在 WebGL 中绘制单个像素

我正在学习Tavares WebGL教程，并陷入泥潭。

我想使用 GL.points 绘制单个像素。我的阵列显然有问题。请参阅FF或Chrome Canary：

http://codepen.io/anon/pen/EPJVjK

/**
 * Creates a program, attaches shaders, links the program.
 * @param {WebGLShader[]} shaders. The shaders to attach.
 */
var createGLProgram = function( gl, shaders ) {
    var program = gl.createProgram();
    for ( var i = 0; i < shaders.length; i += 1 ) {
        gl.attachShader( program, shaders[ i ] );
    }
    gl.linkProgram( program );
    // Check the link status
    var linked = gl.getProgramParameter( program, gl.LINK_STATUS );
    if ( !linked ) {
        // Something went wrong with the link
        var lastError = gl.getProgramInfoLog( program );
        window.console.error( "Error in program linking: " + lastError );
        gl.deleteProgram( program );
        return null;
    }
    return program;
};
var myCreateShader = function( gl, shaderScriptText, shaderType ) {
    // Create the shader object
  var shader = gl.createShader( shaderType );
  // Load the shader source
  gl.shaderSource( shader, shaderScriptText );
  // Compile the shader
  gl.compileShader( shader );
  return shader;
};
// Get A WebGL context.
var canvas = document.getElementById( "canvas" );
var gl = canvas.getContext( "webgl", { antialias: false } )
var vertexShader = myCreateShader( gl,
    `attribute vec2 a_position;
    uniform vec2 u_resolution;
    void main() {
    // convert the rectangle from pixels to 0.0 to 1.0
        vec2 zeroToOne = a_position / u_resolution;
        // convert from 0 -> 1 to 0 -> 2
        vec2 zeroToTwo = zeroToOne * 2.0;
        // convert from 0 -> 2 to -1 -> +1 (clipspace)
        vec2 clipSpace = zeroToTwo - 1.0;
        // Flip 0,0 from bottom left to conventional 2D top left.
        gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
    }`, gl.VERTEX_SHADER );
var fragmentShader = myCreateShader( gl,
    `precision mediump float;
    uniform vec4 u_color;
    void main() {
    gl_FragColor = u_color;
    }`, gl.FRAGMENT_SHADER );
var program = createGLProgram( gl, [ vertexShader, fragmentShader ] );
gl.useProgram( program );
// Store color location.
var colorLocation = gl.getUniformLocation( program, "u_color" );
// Look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation( program, "a_position" );
// Set the resolution.
var resolutionLocation = gl.getUniformLocation( program, "u_resolution");
gl.uniform2f( resolutionLocation, canvas.width, canvas.height);
// Create a buffer.
var buffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, buffer );
gl.enableVertexAttribArray( positionLocation );
// Send the vertex data to the shader program.
gl.vertexAttribPointer( positionLocation, 2, gl.FLOAT, false, 0, 0 );
// Set color to black.
gl.uniform4f( colorLocation, 0, 0, 0, 1);
function drawOneBlackPixel( gl, x, y ) {
    // Fills the buffer with a single point?
    gl.bufferData( gl.ARRAY_BUFFER, new Float32Array([
      x,     y,
            0,     y,
            x,     0,
            x,     0,
            0,     y,
            0,     0]), gl.STATIC_DRAW );
    // Draw one point.
    gl.drawArrays( gl.POINTS, 0, 1 );
}

// These tests are supposed to be x,y coordinates from top left.
drawOneBlackPixel( gl, 0, 0 );
drawOneBlackPixel( gl, 1, 1 );
drawOneBlackPixel( gl, 2, 2 );
drawOneBlackPixel( gl, 3, 3 );
drawOneBlackPixel( gl, 4, 4 );
drawOneBlackPixel( gl, 5, 5 );
drawOneBlackPixel( gl, 6, 6 );
drawOneBlackPixel( gl, 7, 7 );
drawOneBlackPixel( gl, 10, 5 );
drawOneBlackPixel( gl, 15, 5 );
drawOneBlackPixel( gl, 20, 5 );
drawOneBlackPixel( gl, 12, 34 );
drawOneBlackPixel( gl, 42, 42 );

问题是像素渲染得不到位。(0,0( 不会在左上角绘制。而应该是像素的对角线反而被"阶梯"成两个像素的块。一个工作的代码笔将是理想的。

作为第二个"奖励"问题，我接下来希望能够在单个drawArrays调用上批处理多个像素，在requestAnimationFrame上调用。关于如何最好地做到这一点的建议将不胜感激。

附言我读过：

如何使用 WebGL 在画布上设置像素的颜色？

但我的错误似乎比这低一些。请不要建议我使用canvas2D。我想要webGL的性能，我正在尝试从头开始学习:)