GLAPI/glDrawElements: Difference between revisions
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== Function Definition == | == Function Definition == | ||
void '''glDrawElements'''(GLenum | void '''glDrawElements'''(GLenum {{param|mode}}, GLsizei {{param|count}}, GLenum {{param|type}}, const GLvoid * {{param|indices}}); | ||
; mode | ; mode | ||
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: Specifies the number of elements to be rendered. | : Specifies the number of elements to be rendered. | ||
; type | ; type | ||
: Specifies the type of the values in | : Specifies the type of the values in {{param|indices}}. Must be one of {{code|GL_UNSIGNED_BYTE}}, {{code|GL_UNSIGNED_SHORT}}, or {{code|GL_UNSIGNED_INT}}. | ||
; indices | ; indices | ||
: Specifies a pointer to the location where the indices are stored. | : Specifies a pointer to the location where the indices are stored. | ||
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'''glDrawElements''' specifies multiple geometric primitives with very few subroutine calls. Instead of calling a GL function to pass each individual vertex, normal, texture coordinate, edge flag, or color, you can prespecify separate arrays of vertices, normals, and so on, and use them to construct a sequence of primitives with a single call to '''glDrawElements'''. | '''glDrawElements''' specifies multiple geometric primitives with very few subroutine calls. Instead of calling a GL function to pass each individual vertex, normal, texture coordinate, edge flag, or color, you can prespecify separate arrays of vertices, normals, and so on, and use them to construct a sequence of primitives with a single call to '''glDrawElements'''. | ||
When '''glDrawElements''' is called, it uses | When '''glDrawElements''' is called, it uses {{param|count}} sequential elements from an enabled array, starting at {{param|indices}} to construct a sequence of geometric primitives. {{param|mode}} specifies what kind of primitives are constructed and how the array elements construct these primitives. If more than one array is enabled, each is used. | ||
Vertex attributes that are modified by '''glDrawElements''' have an unspecified value after '''glDrawElements''' returns. Attributes that aren't modified maintain their previous values. | Vertex attributes that are modified by '''glDrawElements''' have an unspecified value after '''glDrawElements''' returns. Attributes that aren't modified maintain their previous values. | ||
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== Errors == | == Errors == | ||
{{code|GL_INVALID_ENUM}} is generated if | {{code|GL_INVALID_ENUM}} is generated if {{param|mode}} is not an accepted value. | ||
{{code|GL_INVALID_VALUE}} is generated if | {{code|GL_INVALID_VALUE}} is generated if {{param|count}} is negative. | ||
{{code|GL_INVALID_OPERATION}} is generated if a geometry shader is active and | {{code|GL_INVALID_OPERATION}} is generated if a geometry shader is active and {{param|mode}} is incompatible with the input primitive type of the geometry shader in the currently installed program object. | ||
{{code|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. | {{code|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. | ||
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== See Also == | == See Also == | ||
{{apifunc|glDrawArrays}}, {{apifunc|glDrawElementsInstanced}}, {{apifunc|glDrawElementsBaseVertex}}, {{apifunc|glDrawRangeElements}} | |||
== Copyright == | == Copyright == | ||
Revision as of 01:17, 29 April 2012
| Core in version | 4.6 | |
|---|---|---|
| Core since version | 1.1 | |
glDrawElements: render primitives from array data
Function Definition
void glDrawElements(GLenum mode, GLsizei count, GLenum type, const GLvoid * indices);
- 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 pointer to the location where the indices are stored.
Description
glDrawElements specifies multiple geometric primitives with very few subroutine calls. Instead of calling a GL function to pass each individual vertex, normal, texture coordinate, edge flag, or color, you can prespecify separate arrays of vertices, normals, and so on, and use them to construct a sequence of primitives with a single call to glDrawElements.
When glDrawElements is called, it uses count sequential elements from an enabled array, starting at indices to construct a sequence of geometric primitives. mode specifies what kind of primitives are constructed and how the array elements construct these primitives. If more than one array is enabled, each is used.
Vertex attributes that are modified by glDrawElements have an unspecified value after glDrawElements returns. Attributes that aren't modified maintain their previous values.
Notes
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 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
glDrawArrays, glDrawElementsInstanced, glDrawElementsBaseVertex, glDrawRangeElements
Copyright
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.