GLAPI/glDrawElementsInstancedBaseVertexBaseInstance

glDrawElementsInstancedBaseVertexBaseInstance

Core in version		4.6
Core since version		3.2
Core ARB extension	ARB_base_instance

glDrawElementsInstancedBaseVertexBaseInstance: render multiple instances of a set of primitives from array data with a per-element offset

Function Definition

 void glDrawElementsInstancedBaseVertexBaseInstance(GLenum mode​, GLsizei count​, GLenum type​, GLvoid *indices​, GLsizei primcount​, GLint basevertex​, GLuint baseinstance​);

mode

Specifies what kind of primitives to render. Symbolic constants GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES, GL_LINES_ADJACENCY, GL_LINE_STRIP_ADJACENCY, GL_TRIANGLES_ADJACENCY, GL_TRIANGLE_STRIP_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 indexed geometry that should be drawn.

basevertex

Specifies a constant that should be added to each element of indices​ when chosing elements from the enabled vertex arrays.

baseinstance

Specifies the base instance for use in fetching instanced vertex attributes.

Description

glDrawElementsInstancedBaseVertexBaseInstance behaves identically to glDrawElementsInstanced except that each index fetched from GL_ELEMENT_ARRAY_BUFFER (starting from the byte offset indices​ in bytes) will have basevertex​ added to it before fetching that index from the vertex arrays. If the resulting value is larger than the maximum value representable by type​, it is as if the calculation were upconverted to 32-bit unsigned integers (with wrapping on overflow conditions). The operation is undefined if the sum would be negative.

Specific vertex attributes may be classified as instanced through the use of glVertexAttribDivisor. Instanced vertex attributes supply per-instance vertex data to the vertex shader. The index of the vertex fetched from the enabled instanced vertex attribute arrays is calculated as $ \left\lfloor {\frac {gl\_InstanceID}{divisor}}+baseInstance\right\rfloor $. Note that baseinstance​ does not affect the shader-visible value of gl_InstanceID.

Notes

glDrawElementsInstancedBaseVertexBaseInstance is available only if the GL version is 4.2 or greater.

Errors

GL_INVALID_ENUM is generated if mode​ is not an accepted value.

GL_INVALID_VALUE is generated if count​ or primcount​ is 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 or the element array and the buffer object's data store is currently mapped.

See Also

glBindVertexArray, glDrawArraysInstancedBaseInstance, glDrawElements, glDrawElementsBaseVertex, glDrawElementsIndirect, glDrawElementsInstanced, glDrawElementsInstancedBaseInstance, glDrawElementsInstancedBaseVertex, glDrawRangeElements, glDrawRangeElementsBaseVertex, glMultiDrawElements, glMultiDrawElementsBaseVertex, glMultiDrawElementsIndirect

Copyright

Copyright © 2011 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/.