GLAPI/glDrawElementsInstanced

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glDrawElementsInstanced
Core in version 4.4
Core since version 3.1

glDrawElementsInstanced: draw multiple instances of a set of elements

Function Definition

 void glDrawElementsInstanced(GLenum mode​, GLsizei count​, GLenum type​, const void * indices​, GLsizei primcount​);
mode
Specifies what kind of primitives to render. Symbolic constants GL_POINTS​, GL_LINE_STRIP​, GL_LINE_LOOP​, GL_LINES​, GL_LINE_STRIP_ADJACENCY​, GL_LINES_ADJACENCY​, GL_TRIANGLE_STRIP​, GL_TRIANGLE_FAN​, GL_TRIANGLES​, GL_TRIANGLE_STRIP_ADJACENCY​, GL_TRIANGLES_ADJACENCY​ and GL_PATCHES​ are accepted.
count
Specifies the number of elements to be rendered.
type
Specifies the type of the values in indices​. Must be one of GL_UNSIGNED_BYTE​, GL_UNSIGNED_SHORT​, or GL_UNSIGNED_INT​.
indices
Specifies a byte offset (cast to a pointer type) into the buffer bound to GL_ELEMENT_ARRAY_BUFFER​ to start reading indices from.
primcount
Specifies the number of instances of the specified range of indices to be rendered.

Description

glDrawElementsInstanced behaves identically to glDrawElements except that primcount​ instances of the set of elements are executed and the value of the internal counter instanceID​ advances for each iteration. instanceID​ is an internal 32-bit integer counter that may be read by a vertex shader as gl_InstanceID​.

glDrawElementsInstanced has the same effect as:

    if (mode, count, or type is invalid )
        generate appropriate error
    else {
        for (int i = 0; i < primcount ; i++) {
            instanceID = i;
            glDrawElements(mode, count, type, indices);
        }
        instanceID = 0;
    }

Notes

glDrawElementsInstanced is available only if the GL version is 3.1 or greater.

GL_LINE_STRIP_ADJACENCY​, GL_LINES_ADJACENCY​, GL_TRIANGLE_STRIP_ADJACENCY​ and GL_TRIANGLES_ADJACENCY​ are available only if the GL version is 3.2 or greater.

Errors

GL_INVALID_ENUM​ is generated if mode​ is not one of GL_POINTS​, GL_LINE_STRIP​, GL_LINE_LOOP​, GL_LINES​, GL_TRIANGLE_STRIP​, GL_TRIANGLE_FAN​, or GL_TRIANGLES​.

GL_INVALID_VALUE​ is generated if count​ or primcount​ are negative.

GL_INVALID_OPERATION​ is generated if a geometry shader is active and mode​ is incompatible with the input primitive type of the geometry shader in the currently installed program object.

GL_INVALID_OPERATION​ is generated if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped.

See Also

glBindVertexArray, glDrawArraysInstanced, glDrawElements, glDrawElementsBaseVertex, glDrawElementsIndirect, glDrawElementsInstancedBaseInstance, glDrawElementsInstancedBaseVertex, glDrawElementsInstancedBaseVertexBaseInstance, glDrawRangeElements, glDrawRangeElementsBaseVertex, glMultiDrawElements, glMultiDrawElementsBaseVertex, glMultiDrawElementsIndirect

Copyright

Copyright © 2010 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.