glDrawElements function

Artikkel
12/11/2020

The glDrawElements function renders primitives from array data.

Syntax

void WINAPI glDrawElements(
         GLenum  mode,
         GLsizei count,
         GLenum  type,
   const GLvoid  *indices
);

Parameters

mode: The kind of primitives to render. It can assume one of the following symbolic values: GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES, GL_QUAD_STRIP, GL_QUADS, and GL_POLYGON.
count: The number of elements to be rendered.
type: The type of the values in indices. Must be one of GL_UNSIGNED_BYTE, GL_UNSIGNED_SHORT, or GL_UNSIGNED_INT.
indices: A pointer to the location where the indices are stored.

Return value

This function does not return a value.

Error codes

The following error codes can be retrieved by the glGetError function.

Name	Meaning
GL_INVALID_ENUM	mode was not an accepted value.
GL_INVALID_VALUE	count was a negative value.
GL_INVALID_OPERATION	The function was called between a call to glBegin and the corresponding call to glEnd.

Remarks

The glDrawElements function enables you to specify multiple geometric primitives with very few function calls. Instead of calling an OpenGL function to pass each individual vertex, normal, or color, you can specify separate arrays of vertices, normals, and colors beforehand and use them to define a sequence of primitives (all of the same type) with a single call to glDrawElements.

When you call the glDrawElements function, it uses count sequential elements from indices to construct a sequence of geometric primitives. The mode parameter specifies what kind of primitives are constructed, and how the array elements are used to construct these primitives. If GL_VERTEX_ARRAY is not enabled, no geometric primitives are generated.

Vertex attributes that are modified by glDrawElements have an unspecified value after glDrawElements returns. For example, if GL_COLOR_ARRAY is enabled, the value of the current color is undefined after glDrawElements executes. Attributes that aren't modified remain unchanged.

You can include the glDrawElements function in display lists. When glDrawElements is included in a display list, the necessary array data (determined by the array pointers and enables) is also entered into the display list. Because the array pointers and enables are client-side state variables, their values affect display lists when the lists are created, not when the lists are executed.

Note

The glDrawElements function is only available in OpenGL version 1.1 or later.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Gl.h
Library	Opengl32.lib
DLL	Opengl32.dll

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