WebGL - Problems Loading a Texture

Question

I am trying to create a texture (just grey everywhere) and render it to a canvas using WebGL.

I have attempted here:

function tryToDraw() {
  vertexShaderCode = `#version 100
      precision mediump float;
      attribute vec2 vertex_attrib;

      void main (void)
      {
          gl_Position = vec4 (vertex_attrib, 0.0, 1.0) ;
      }
  `;

  fragmentShaderCode = `#version 100
      precision mediump float;

      uniform sampler2D myTexture;

      void main (void) {
          vec2 texcoord = gl_FragCoord.xy / 1024.0;
          gl_FragColor = vec4(texture2D (myTexture, texcoord).rgb, 1.0);
      }
  `;

  var canvas = document.getElementById('waves_canvas');
  var gl = canvas.getContext('webgl');
  var program = gl.createProgram();

  var textureArr = new Uint8Array(1024 * 1024 * 3).fill(128);

  var vertexShader = gl.createShader(gl.VERTEX_SHADER);
  gl.shaderSource(vertexShader, vertexShaderCode);
  gl.compileShader(vertexShader);
  gl.attachShader(program, vertexShader);

  var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
  gl.shaderSource(fragmentShader, fragmentShaderCode);
  gl.compileShader(fragmentShader);
  gl.attachShader(program, fragmentShader);

  gl.linkProgram(program);
  gl.validateProgram(program);
  console.log(gl.getProgramParameter(program, gl.VALIDATE_STATUS));
  gl.useProgram(program);

  var location = gl.getUniformLocation(program, 'myTexture');
  gl.uniform1i(location, 0);
  var texture = gl.createTexture();
  gl.activeTexture(gl.TEXTURE0);
  gl.bindTexture(gl.TEXTURE_2D, texture);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, 1024, 1024, 0, gl.RGB, gl.UNSIGNED_BYTE, textureArr);

  var vertexPositions = new Float32Array([-1.0, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0]);
  var vertexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, vertexPositions, gl.STATIC_DRAW);

  var vPosAttrLoc = gl.getAttribLocation(program, 'vertex_attrib');
  gl.enableVertexAttribArray(vPosAttrLoc);
  gl.vertexAttribPointer(vPosAttrLoc, 2, gl.FLOAT, false, 2 * vertexPositions.BYTES_PER_ELEMENT, null);
  gl.drawArrays(gl.TRIANGLES, 0, 6);
}

tryToDraw();

<canvas id="waves_canvas"></canvas>

My understanding of loading textures in WebGL is that we load textures according to the following procedure:

• We specify which texture unit we use for our uniform sampler2D by using gl.uniform1i(gl.getUniformLocation(program, 'myTexture'), 0).
• We create a texture using gl.createTexture().
• We then choose which texture unit we want to load onto using GL.activeTexture.
• We bind the texture we just created to the texture unit by using GL.bindTexture.
• We load the texture using GL.texImage2D.

I've tried to implement it in the JSFiddle above, but I don't think the texture is loading correctly. I'm expecting to see a grey screen (128,128,128) which should be the texture I loaded, however all I see is a black screen.

Does anyone know if I am loading the texture correctly?

Answer 1

When I run your code in Chrome I get this warning in the JavaScript console

[.WebGL-0x7f9d4101ce00]RENDER WARNING: texture bound to texture unit 0 is not renderable. It might be non-power-of-2 or have incompatible texture filtering (maybe)?

Your texture has no mips so you either need to create mips by calling gl.generateMipmap(gl.TEXTURE_2D) or you need to set the filtering so mips are not needed by calling gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)

See this

function tryToDraw() {
  vertexShaderCode = `#version 100
      precision mediump float;
      attribute vec2 vertex_attrib;

      void main (void)
      {
          gl_Position = vec4 (vertex_attrib, 0.0, 1.0) ;
      }
  `;

  fragmentShaderCode = `#version 100
      precision mediump float;

      uniform sampler2D myTexture;

      void main (void) {
          vec2 texcoord = gl_FragCoord.xy / 1024.0;
          gl_FragColor = vec4(texture2D (myTexture, texcoord).rgb, 1.0);
      }
  `;

  var canvas = document.getElementById('waves_canvas');
  var gl = canvas.getContext('webgl');
  var program = gl.createProgram();

  var textureArr = new Uint8Array(1024 * 1024 * 3).fill(128);

  var vertexShader = gl.createShader(gl.VERTEX_SHADER);
  gl.shaderSource(vertexShader, vertexShaderCode);
  gl.compileShader(vertexShader);
  gl.attachShader(program, vertexShader);

  var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
  gl.shaderSource(fragmentShader, fragmentShaderCode);
  gl.compileShader(fragmentShader);
  gl.attachShader(program, fragmentShader);

  gl.linkProgram(program);
  gl.validateProgram(program);
  console.log(gl.getProgramParameter(program, gl.VALIDATE_STATUS));
  gl.useProgram(program);

  var location = gl.getUniformLocation(program, 'myTexture');
  gl.uniform1i(location, 0);
  var texture = gl.createTexture();
  gl.activeTexture(gl.TEXTURE0);
  gl.bindTexture(gl.TEXTURE_2D, texture);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, 1024, 1024, 0, gl.RGB, gl.UNSIGNED_BYTE, textureArr);

  var vertexPositions = new Float32Array([-1.0, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0]);
  var vertexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, vertexPositions, gl.STATIC_DRAW);

  var vPosAttrLoc = gl.getAttribLocation(program, 'vertex_attrib');
  gl.enableVertexAttribArray(vPosAttrLoc);
  gl.vertexAttribPointer(vPosAttrLoc, 2, gl.FLOAT, false, 2 * vertexPositions.BYTES_PER_ELEMENT, null);
  gl.drawArrays(gl.TRIANGLES, 0, 6);
}

tryToDraw();

<canvas id="waves_canvas"></canvas>

Please use a snippet next time.