glRenderMode
NAME
glRenderMode -- set rasterization mode
C SPECIFICATION
GLint glRenderMode(GLenum mode)
PARAMETERS
- mode
-
Specifies the rasterization mode. Three values are accepted:
GL_RENDER, GL_SELECT, and GL_FEEDBACK.
The default value is GL_RENDER.
DESCRIPTION
glRenderMode sets the rasterization mode. It takes one argument,
mode, which can assume one of three predefined values:
- GL_RENDER
-
Render mode. Primitives are rasterized, producing pixel fragments,
which are written into the frame buffer. This is the normal mode
and also the default mode.
- GL_SELECT
-
Selection mode. No pixel fragments are produced, and no change to
the frame buffer contents is made. Instead, a record of the names
of primitives that would have been drawn if the render mode was
GL_RENDER is returned in a select buffer, which must be
created (see
glSelectBuffer)
before selection mode is entered.
- GL_FEEDBACK
-
Feedback mode. No pixel fragments are produced, and no change to
the frame buffer contents is made. Instead, the coordinates and
attributes of vertices that would have been drawn had the render
mode been GL_RENDER is returned in a feedback buffer, which
must be created (see
glFeedbackBuffer)
before feedback mode is entered.
The return value of glRenderMode is determined by the render mode
at the time glRenderMode is called, rather than by mode.
The values returned for the three render modes are as follows:
- GL_RENDER
-
Zero.
- GL_SELECT
-
The number of hit records transferred to the select buffer.
- GL_FEEDBACK
-
The number of values (not vertices) transferred to the feedback buffer.
Refer to the
glSelectBuffer and
glFeedbackBuffer
reference pages for more details concerning selection and feedback operation.
NOTES
If an error is generated, glRenderMode returns zero regardless of the
current render mode.
ERRORS
GL_INVALID_ENUM is generated if mode is not one of the three
accepted values.
GL_INVALID_OPERATION is generated if
glSelectBuffer
is called while the render mode is GL_SELECT, or if glRenderMode
is called with argument GL_SELECT before
glSelectBuffer
is called at least once.
GL_INVALID_OPERATION is generated if
glFeedbackBuffer
is called while the render mode is GL_FEEDBACK, or if
glRenderMode is called with argument GL_FEEDBACK before
glFeedbackBuffer
is called at least once..
GL_INVALID_OPERATION is generated if glRenderMode is called
between a call to glBegin and the
corresponding call to glEnd.
ASSOCIATED GETS
glGet with argument
GL_RENDER_MODE
SEE ALSO
glFeedbackBuffer,
glInitNames,
glLoadName,
glPassThrough,
glPushName,
glSelectBuffer
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© 1995 Uwe Behrens. All rights reserved.