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QB64-PE/internal/help/_glDrawArrays.txt
2016-03-18 08:36:04 -03:00

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'''_glDrawArrays:''' render primitives from array data
{{PageSyntax}}
:: SUB _glDrawArrays (BYVAL mode AS _UNSIGNED LONG, BYVAL first AS LONG, BYVAL count AS LONG)
:: void '''_glDrawArrays'''(GLenum {{Parameter|mode}}, GLint {{Parameter|first}}, GLsizei {{Parameter|count}});
; mode
: Specifies what kind of primitives to render. Symbolic constants {{KW|_GL_POINTS}}, {{KW|_GL_LINE_STRIP}}, {{KW|_GL_LINE_LOOP}}, {{KW|_GL_LINES}}, {{KW|_GL_LINE_STRIP_ADJACENCY}}, {{KW|_GL_LINES_ADJACENCY}}, {{KW|_GL_TRIANGLE_STRIP}}, {{KW|_GL_TRIANGLE_FAN}}, {{KW|_GL_TRIANGLES}}, {{KW|_GL_TRIANGLE_STRIP_ADJACENCY}}, {{KW|_GL_TRIANGLES_ADJACENCY}} and {{KW|_GL_PATCHES}} are accepted.
; first
: Specifies the starting index in the enabled arrays.
; count
: Specifies the number of indices to be rendered.
{{PageDescription}}
'''_glDrawArrays''' specifies 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 vertices, normals, and colors and use them to construct a sequence of primitives with a single call to '''_glDrawArrays'''.
When '''_glDrawArrays''' is called, it uses {{Parameter|count}} sequential elements from each enabled array to construct a sequence of geometric primitives, beginning with element {{Parameter|first}}. {{Parameter|mode}} specifies what kind of primitives are constructed and how the array elements construct those primitives.
Vertex attributes that are modified by '''_glDrawArrays''' have an unspecified value after '''_glDrawArrays''' returns. Attributes that aren't modified remain well defined.
{{PageNotes}}
{{KW|_GL_LINE_STRIP_ADJACENCY}}, {{KW|_GL_LINES_ADJACENCY}}, {{KW|_GL_TRIANGLE_STRIP_ADJACENCY}} and {{KW|_GL_TRIANGLES_ADJACENCY}} are available only if the GL version is 3.2 or greater.
{{PageErrors}}
{{KW|_GL_INVALID_ENUM}} is generated if {{Parameter|mode}} is not an accepted value.
{{KW|_GL_INVALID_VALUE}} is generated if {{Parameter|count}} is negative.
{{KW|_GL_INVALID_OPERATION}} is generated if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped.
{{KW|_GL_INVALID_OPERATION}} is generated if a geometry shader is active and {{Parameter|mode}} is incompatible with the input primitive type of the geometry shader in the currently installed program object.
{{PageSeeAlso}}
{{KW|_GL}}
{{KW|_glBindVertexArray}}, {{KW|_glDrawArraysIndirect}}, {{KW|_glDrawArraysInstanced}}, {{KW|_glDrawArraysInstancedBaseInstance}}, {{KW|_glMultiDrawArrays}}, {{KW|_glMultiDrawArraysIndirect}}
{{PageCopyright}}