glBeginTransformFeedback — start transform feedback operation
void glBeginTransformFeedback(
|
GLenum primitiveMode) ; |
void glEndTransformFeedback(
|
void) ; |
glBeginTransformFeedback
primitiveMode
Specify the output type of the primitives that will be recorded into the buffer objects that are bound for transform feedback.
Transform feedback mode captures the values of varying variables written by the vertex shader (or, if active, the geometry shader).
Transform feedback is said to be active after a call to glBeginTransformFeedback
until a subsequent call to glEndTransformFeedback
.
Transform feedback commands must be paired. An implicit glResumeTransformFeedback
is performed by glEndTransformFeedback
if the transform feedback is paused.
Transform feedback is restricted to non-indexed GL_POINTS
, GL_LINES
, and
GL_TRIANGLES
.
If no geometry shader is present, while transform feedback is active the mode
parameter to
glDrawArrays and other drawing commands must match those specified
in the following table:
Transform Feedback primitiveMode
|
Allowed Render Primitive modes
|
---|---|
GL_POINTS |
GL_POINTS |
GL_LINES |
GL_LINES ,
GL_LINE_LOOP ,
GL_LINE_STRIP ,
GL_LINES_ADJACENCY ,
GL_LINE_STRIP_ADJACENCY
|
GL_TRIANGLES
|
GL_TRIANGLES ,
GL_TRIANGLE_STRIP ,
GL_TRIANGLE_FAN ,
GL_TRIANGLES_ADJACENCY ,
GL_TRIANGLE_STRIP_ADJACENCY
|
If a geometry shader is present, the output primitive type from the geometry shader must match those provided in the following table:
Transform Feedback primitiveMode
|
Allowed Geometry Shader Output Primitive Type |
---|---|
GL_POINTS |
points |
GL_LINES |
line_strip |
GL_TRIANGLES |
triangle_strip |
Geometry shaders, and the GL_TRIANGLES_ADJACENCY
, GL_TRIANGLE_STRIP_ADJACENCY
,
GL_LINES_ADJACENCY
and GL_LINE_STRIP_ADJACENCY
primtive modes are available
only if the GL ES version is 3.2 or greater.
GL_INVALID_OPERATION
is generated if glBeginTransformFeedback
is executed
while transform feedback is active.
GL_INVALID_ENUM
is generated by glBeginTransformFeedback
if primitiveMode
is not one of GL_POINTS
, GL_LINES
, or GL_TRIANGLES
.
GL_INVALID_OPERATION
is generated if glEndTransformFeedback
is executed
while transform feedback is not active.
GL_INVALID_OPERATION
is generated by glDrawArrays
and other drawing commands if transform feedback is active
and mode
is not compatible with primitiveMode
as described above.
GL_INVALID_OPERATION
is generated by glBeginTransformFeedback
if any binding
point used in transform feedback mode does not have a buffer object bound. In interleaved mode, only the first buffer
object binding point is ever written to.
GL_INVALID_OPERATION
is generated by glBeginTransformFeedback
if no binding
points would be used, either because no program object is active of because the active program object has specified
no varying variables to record.
OpenGL ES API Version | ||||
---|---|---|---|---|
Function Name | 2.0 | 3.0 | 3.1 | 3.2 |
glBeginTransformFeedback
|
- | ✔ | ✔ | ✔ |
glEndTransformFeedback
|
- | ✔ | ✔ | ✔ |
Copyright © 2010-2015 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. https://opencontent.org/openpub/.