glMultiDrawArraysEXT Subroutine

OpenGL 1.2 for AIX: Reference Manual

glMultiDrawArraysEXT Subroutine

Purpose

Renders multiple primitives from array data.

Library

OpenGL C bindings library: libGL.a

C Syntax

void glMultiDrawArraysEXT(GLenum mode,
                          GLint *first,
                          GLsizei *count,
                          GLsizei primcount)

Description

The glMultiDrawArraysEXT subroutine lets you specify multiple geometric primitives with very few subroutine calls. Instead of calling a GL procedure to pass each individual vertex, normal, texture coordinate, edge flag, or color, you can prespecify separate arrays of vertexes, normals, and colors and use them to construct a sequence of primitives with a single call to glMultiDrawArraysEXT.

When glMultiDrawArraysEXT is called, it uses count sequential elements from each enabled array to construct a sequence of geometric primitives, beginning with element first. The mode parameter specifies what kind of primitives are constructed, and how the array elements construct these primitives. If GL_VERTEX_ARRAY is not enabled, no geometric primitives are generated.

Vertex attributes that are modified by glMultiDrawArraysEXT have an unspecified value after glMultiDrawArraysEXT returns. For example, if GL_COLOR_ARRAY is enabled, the value of the current color is undefined after glMultiDrawArraysEXT executes. Attributes that are not modified remain well defined.

Behaves identically to DrawArrays except that a list of arrays is specified instead. The number of lists is specified in the primcount parameter. It has the same effect as:

        for(i=0; i<primcount; i++) {
           if (*(count+i)>0) DrawArrays(mode, *(first+i), *(count+i));
        }

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.
first	Points to an array of the starting indeces in the enabled arrays.
count	Points to an array of the number of indices to be rendered.
primcount	Specifies the size of first and count.

Notes

The glMultiDrawArraysEXT subroutine is included in display lists. If glMultiDrawArraysEXT 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 glMultiDrawArraysEXT is executed between the execution of glBegin and the corresponding glEnd.

Related Information

The glArrayElement subroutine, glColorPointer subroutine, glMultiDrawElementsEXT subroutine, glEdgeFlagPointer subroutine, glGetPointerv subroutine, glIndexPointer subroutine, glNormalPointer subroutine, glTexCoordPointer subroutine, glVertexPointer subroutine.