glDrawElements

Name

glDrawElements — render primitives from array data

C Specification

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

Parameters

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_QUAD_STRIP, GL_QUADS, and GL_POLYGON 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.  diffrent type diffrent size of array size;

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. If GL_VERTEX_ARRAY is not enabled, no geometric primitives are constructed.

　　Vertex attributes that are modified by glDrawElements have an unspecified value after glDrawElements returns. For example, ifGL_COLOR_ARRAY is enabled, the value of the current color is undefined after glDrawElements executes. Attributes that aren't modified maintain their previous values.

Notes

　　glDrawElements is available only if the GL version is 1.1 or greater.

　　glDrawElements is included in display lists. If glDrawElements is entered into 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, their values affect display lists when the lists are created, not when the lists are executed.

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 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.

　　GL_INVALID_OPERATION is generated if glDrawElements is executed between the execution of glBegin and the corresponding glEnd.