NAME¶
gl_Position - contains the position of the current vertex
DECLARATION¶
gl_Position is a member of the
gl_PerVertex named block:
out gl_PerVertex {
vec4 gl_Position;
float gl_PointSize;
float gl_ClipDistance[];
};
DESCRIPTION¶
In the vertex, tessellation evaluation and geometry languages, a single global
instance of the
gl_PerVertex named block is available and its
gl_Position member is an output that receives the homogeneous vertex
position. It may be written at any time during shader execution. The value
written to
gl_Position will be used by primitive assembly, clipping,
culling and other fixed functionality operations, if present, that operate on
primitives after vertex processing has occurred.
In the tessellation control language, the
gl_PerVertex named block is
used to construct an array,
gl_out[], whose
gl_Position members
hold the homogeneous control point position, which become available as inputs
to the subsequent tessellation evaluation shader.
The value of
gl_Position (or the
gl_Position member of the
gl_out[] array, in the case of the tessellation control shader) is
undefined after the vertex, tessellation control, and tessellation evaluation
shading stages if the corresponding shader executable does not write to
gl_Position. It is also undefined after the geometry processing stage if the
geometry shader executable calls
EmitVertex() without having written
gl_Position since the last call to
EmitVertex() (or hasn't
written it at all).
In the tessellation control, tessellation evaluation and geometry languages, the
gl_PerVertex named block is used to construct an array,
gl_in[]
of per-vertex or per-control point inputs whose content represents the
corresponding outputs written by the previous stage.
VERSION SUPPORT¶
|
OpenGL Shading Language Version |
|
|
|
|
|
|
|
|
|
|
|
Function Name |
1.10 |
1.20 |
1.30 |
1.40 |
1.50 |
3.30 |
4.00 |
4.10 |
4.20 |
4.30 |
4.40 |
4.50 |
gl_Position |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
✔ |
Versions 1.10 to 1.40 - vertex shader only.
Versions 1.50 to 3.30 - vertex and geometry shaders only.
SEE ALSO¶
gl_PointSize(),
gl_ClipDistance()
COPYRIGHT¶
Copyright © 2011-2014 Khronos Group. This material may be distributed
subject to the terms and conditions set forth in the Open Publication License,
v 1.0, 8 June 1999.
http://opencontent.org/openpub/.
COPYRIGHT¶
Copyright © 2011-2014 Khronos Group