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glRenderMode - set rasterization mode
GLenum mode )
sets the rasterization mode. It takes one argument, mode, which can assume
one of three predefined values:
- Specifies the rasterization mode. Three values are accepted:
GL_RENDER, GL_SELECT, and GL_FEEDBACK. The initial value is 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.
- 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 had been GL_RENDER is returned in a select buffer,
which must be created (see glSelectBuffer) before selection mode is entered.
- 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 if the render mode had 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:
- The number of hit records transferred to the select buffer.
- The number of values (not vertices) transferred to the feedback
See the glSelectBuffer and glFeedbackBuffer reference pages for
more details concerning selection and feedback operation.
If an error
is generated, glRenderMode returns 0 regardless of the current render mode.
GL_INVALID_ENUM is generated if mode is not one of the three accepted
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.
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 executed between the execution of glBegin and the corresponding execution
glGet with argument GL_RENDER_MODE
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