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WebGL2RenderingContext: vertexAttribIPointer() method

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.

Return value

None (undefined).

Description

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>

Specifications

Specification
WebGL 2.0 Specification # 3.7.8

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`vertexAttribIPointer`	56	79	51	No	43	15	58	58	51	43	15	7.0