WEBGL_multi_draw.multiDrawElementsInstancedWEBGL()

The WEBGL_multi_draw.multiDrawElementsWEBGL() method of the WebGL API renders multiple primitives from array data. It is identical to multiple calls to the gl.drawElementsInstanced() method.

Syntax

void ext.multiDrawElementsInstancedWEBGL(mode,
    countsList, countsOffset,
    type,
    firstsList, firstsOffset,
    instanceCountsList, instanceCountsOffset,
    drawCount);

Parameters

mode

A GLenum specifying the type primitive to render. Possible values are:

• gl.POINTS: Draws a single dot.
• gl.LINE_STRIP: Draws a straight line to the next vertex.
• gl.LINE_LOOP: Draws a straight line to the next vertex, and connects the last vertex back to the first.
• gl.LINES: Draws a line between a pair of vertices.
• gl.TRIANGLE_STRIP
• gl.TRIANGLE_FAN
• gl.TRIANGLES: Draws a triangle for a group of three vertices.

countsList

An Int32Array or Array (of GLint) specifying a list of numbers of indices to be rendered.

countsOffset

A GLUint defining the starting point into the countsList array.

type

A GLenum specifying the type of the values in the element array buffer. Possible values are:

• gl.UNSIGNED_BYTE
• gl.UNSIGNED_SHORT
• When using the OES_element_index_uint extension:
  • gl.UNSIGNED_INT

offsetsList

An Int32Array or Array (of GLsizei) specifying a list of starting indices for the arrays of vector points.

offsetsOffset

A GLuint defining the starting point into the offsetsList array.

instanceCountsList

An Int32Array or Array (of GLsizei) specifying a list of number sof instances of the range of elements to execute.

instanceCountsOffset

A GLuint defining the starting point into the instanceCountsList array.

drawCount

A GLsizei specifying the number of instances of the range of elements to execute.

Return value

None.

Exceptions

• If mode is not one of the accepted values, a gl.INVALID_ENUM error is thrown.
• If drawCount or items in countsList, offsetsList, or instanceCountsList are negative, a gl.INVALID_VALUE error is thrown.

Examples

// let counts = new Int32Array(...);
// let offsets = new Int32Array(...);
// let instanceCounts = new Int32Array(...);
ext.multiDrawElementsInstancedWEBGL(
    gl.TRIANGLES, counts, 0, gl.UNSIGNED_SHORT, offsets, 0, instanceCounts, 0,
    counts.length);
}

Specifications

Browser compatibility

See also

• WebGLRenderingContext.drawElements()
• WebGL2RenderingContext.drawElementsInstanced()