GLAPI/glDrawElementsInstancedBaseVertexBaseInstance

From OpenGL.org
Jump to: navigation, search
glDrawElementsInstancedBaseVertexBaseInstance
Core in version 4.4
Core since version 4.2
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/.