point-with-gl-pointcoord-in-fragment-shader.html

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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL Point with gl_PointCoord in Fragment Shader Test</title>
<link rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../js/js-test-pre.js"></script>
<script src="../../js/webgl-test-utils.js"></script>
</head>
<body>
<div id="description"></div>
<canvas id="canvas" width="64" height="64"> </canvas>
<div id="console"></div>
<script id="vs" type="x-shader/x-vertex">
varying vec4 v_color;

// The X and Y coordinates of the center of the point.
attribute vec2 a_vertex;

uniform float u_pointSize;

void main(void) {
  gl_PointSize = u_pointSize;
  gl_Position = vec4(a_vertex, 0.0, 1.0);

  // The color of the point.
  v_color = vec4(0.0, 1.0, 0.0, 1.0);
}

</script>
<script id="fs" type="x-shader/x-fragment">
precision mediump float;

varying vec4 v_color;

void main(void) {
  // It seems as long as this mathematical expression references
  // gl_PointCoord, the fragment's color is incorrect.
  vec2 diff = gl_PointCoord - vec2(.5, .5);
  if (length(diff) > 0.5)
    discard;

  // The point should be a solid color.
  gl_FragColor = v_color;
}
</script>
<script>
"use strict";
// Radar 13239314
description("This is a regression test for a graphics driver bug affecting end caps on roads in MapsGL.");

debug("");

var wtu = WebGLTestUtils;
var canvas = document.getElementById("canvas");
var canvasWidth = canvas.width;
var canvasHeight = canvas.height;
var output = document.getElementById("console");
var gl = wtu.create3DContext(canvas);

function runTest() {
  var pointSizeRange = gl.getParameter(gl.ALIASED_POINT_SIZE_RANGE);
  // This test can't really run without a maximum point size of at least 2
  if (pointSizeRange[1] < 2.0) {
    debug("This test needs a maximum ALIASED_POINT_SIZE_RANGE of at least 2");
    return;
  }

  var vs = wtu.loadShaderFromScript(gl, "vs", gl.VERTEX_SHADER);
  var fs = wtu.loadShaderFromScript(gl, "fs", gl.FRAGMENT_SHADER);
  if (!vs || !fs) {
    testFailed("Loading shaders failed");
    return;
  }

  var program = wtu.setupProgram(gl, [vs, fs], ['a_vertex']);
  if (!program) {
    testFailed("Loading program failed");
    return;
  }

  gl.useProgram(program);
  gl.clearColor(0, 0, 0, 1.0);
  gl.disable(gl.DEPTH_TEST);
  gl.clear(gl.COLOR_BUFFER_BIT);

  // uniform float u_pointSize;
  var uni = gl.getUniformLocation(program, 'u_pointSize');
  gl.uniform1f(uni, Math.min(20.0, pointSizeRange[1]));

  // vertex
  var buffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
  var vertexData = new Float32Array([
    0, 0,
  ]);
  gl.bufferData(gl.ARRAY_BUFFER, vertexData, gl.STATIC_DRAW);
  gl.enableVertexAttribArray(0);
  gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);

  gl.drawArrays(gl.POINTS, 0, 1);
  wtu.checkCanvasRect(gl, canvasWidth / 2, canvasHeight / 2, 1, 1,
      [0, 255, 0, 255], "Center pixel should be green", 2);
}

runTest();

debug("");
var successfullyParsed = true;
</script>
<script src="../../js/js-test-post.js"></script>
</body>
</html>