WebGL2RenderingContext: vertexAttribIPointer() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨September 2021⁩.

Note: This feature is available in Web Workers.

The WebGL2RenderingContext.vertexAttribIPointer() method of the WebGL 2 API specifies integer data formats and locations of vertex attributes in a vertex attributes array.

Syntax

vertexAttribIPointer(index, size, type, stride, offset)

Parameters

index: A GLuint specifying the index of the vertex attribute that is to be modified.
size: A GLint specifying the number of components per vertex attribute. Must be 1, 2, 3, or 4.
type: A GLenum specifying the data type of each component in the array. Must be one of: gl.BYTE, gl.UNSIGNED_BYTE, gl.SHORT, gl.UNSIGNED_SHORT, gl.INT, or gl.UNSIGNED_INT.
stride: A GLsizei specifying the offset in bytes between the beginning of consecutive vertex attributes.
offset: A GLintptr specifying an offset in bytes of the first component in the vertex attribute array. Must be a multiple of type.

Very similar to WebGLRenderingContext.vertexAttribPointer(). The main difference is that while values specified by vertexAttribPointer are always interpreted as floating-point values in the shader (even if they were originally specified as integers in the buffer), this method allows specifying values which are interpreted as integers in the shader.

Examples

Linear Blend Skinning

// Describe the layout of the buffer:
// 1. position
gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 20, 0);
gl.enableVertexAttribArray(0);
// 2. bone weights, normalized to [0, 1]
gl.vertexAttribPointer(1, 4, gl.UNSIGNED_BYTE, true, 20, 12);
gl.enableVertexAttribArray(1);
// 3. bone indices, interpreted as integer
gl.vertexAttribIPointer(2, 4, gl.UNSIGNED_BYTE, 20, 16);
gl.enableVertexAttribArray(2);

// Connect to attributes from the vertex shader
gl.bindAttribLocation(shaderProgram, 0, "position");
gl.bindAttribLocation(shaderProgram, 1, "boneWeights");
gl.bindAttribLocation(shaderProgram, 2, "boneIndices");

html

<script id="shader-vs" type="x-shader/x-vertex">
  #version 300 es

  uniform mat4 mvMatrix;
  uniform mat4 bones[120];

  in vec3 position;
  in vec4 boneWeights;
  in uvec4 boneIndices;//read as 4-component unsigned integer

  void main() {
      vec4 skinnedPosition =
          bones[boneIndices.s] * vec4(position, 1.0) * boneWeights.s +
          bones[boneIndices.t] * vec4(position, 1.0) * boneWeights.t +
          bones[boneIndices.p] * vec4(position, 1.0) * boneWeights.p +
          bones[boneIndices.q] * vec4(position, 1.0) * boneWeights.q;
      gl_Position = mvMatrix * skinnedPosition;
  }
</script>