Difference between revisions of "GLAPI/glDrawElementsBaseVertex"

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m (Bot: Adding better formatting.)
(Better indices specification.)
 
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: Specifies the type of the values in indices. Must be one of {{enum|GL_UNSIGNED_BYTE}}, {{enum|GL_UNSIGNED_SHORT}}, or {{enum|GL_UNSIGNED_INT}}.
 
: Specifies the type of the values in indices. Must be one of {{enum|GL_UNSIGNED_BYTE}}, {{enum|GL_UNSIGNED_SHORT}}, or {{enum|GL_UNSIGNED_INT}}.
 
; indices
 
; indices
: Specifies a pointer to the location where the indices are stored.
+
: Specifies a byte offset (cast to a pointer type) into the buffer bound to {{enum|GL_ELEMENT_ARRAY_BUFFER}} to start reading indices from.
 
; basevertex
 
; basevertex
 
: Specifies a constant that should be added to each element of {{param|indices}} when chosing elements from the enabled vertex arrays.
 
: Specifies a constant that should be added to each element of {{param|indices}} when chosing elements from the enabled vertex arrays.
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== Description ==
 
== Description ==
  
'''glDrawElementsBaseVertex''' behaves identically to {{apifunc|glDrawElements}} except that the ''i''th element transferred by the corresponding draw call will be taken from element {{param|indices}}[i] + {{param|basevertex}} of each enabled array. If the resulting value is larger than the maximum value representable by {{param|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.
+
'''glDrawElementsBaseVertex''' behaves identically to {{apifunc|glDrawElements}} except that each index fetched from {{enum|GL_ELEMENT_ARRAY_BUFFER}} (starting from the byte offset {{param|indices}} in bytesbytes) will have {{param|basevertex}} added to it before fetching that index from the vertex arrays. If the resulting index is larger than the maximum value representable by {{param|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.
  
== Notes ==
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The {{code|gl_VertexID}} passed to the [[Vertex Shader]] will be the index after being offset by {{param|basevertex}}, not the index fetched from the buffer.
  
'''glDrawElementsBaseVertex'''{{code|ARB_draw_elements_base_vertex}}== Errors ==
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== Errors ==
  
 
{{enum|GL_INVALID_ENUM}} is generated if {{param|mode}} is not an accepted value.
 
{{enum|GL_INVALID_ENUM}} is generated if {{param|mode}} is not an accepted value.

Latest revision as of 00:19, 31 July 2013

glDrawElementsBaseVertex
Core in version 4.5
Core since version 3.2
Core ARB extension ARB_draw_elements_base_vertex


glDrawElementsBaseVertex: render primitives from array data with a per-element offset

Function Definition

 void glDrawElementsBaseVertex(GLenum mode​, GLsizei count​, GLenum type​, GLvoid *indices​, GLint basevertex​);
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.
basevertex
Specifies a constant that should be added to each element of indices​ when chosing elements from the enabled vertex arrays.

Description

glDrawElementsBaseVertex behaves identically to glDrawElements except that each index fetched from GL_ELEMENT_ARRAY_BUFFER (starting from the byte offset indices​ in bytesbytes) will have basevertex​ added to it before fetching that index from the vertex arrays. If the resulting index 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.

The gl_VertexID​ passed to the Vertex Shader will be the index after being offset by basevertex​, not the index fetched from the buffer.

Errors

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

GL_INVALID_VALUE is generated if count​ 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, glDrawElements, glDrawElementsIndirect, glDrawElementsInstanced, 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/.