fglRenderMode(3G) OpenGL Reference fglRenderMode(3G)NAMEfglRenderMode - set rasterization mode
FORTRAN SPECIFICATION
INTEGER*4 fglRenderMode( INTEGER*4 mode )
PARAMETERS
mode Specifies the rasterization mode. Three values are accepted:
GL_RENDER, GL_SELECT, and GL_FEEDBACK. The initial value is
GL_RENDER.
DESCRIPTIONfglRenderMode 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 had been GL_RENDER is returned
in a select buffer, which must be created (see
fglSelectBuffer) 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 if the render mode had been GL_RENDER is
returned in a feedback buffer, which must be created (see
fglFeedbackBuffer) before feedback mode is entered.
The return value of fglRenderMode is determined by the render mode at the
time fglRenderMode is called, rather than by mode. The values returned
for the three render modes are as follows:
GL_RENDER 0.
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.
See the fglSelectBuffer and fglFeedbackBuffer reference pages for more
details concerning selection and feedback operation.
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fglRenderMode(3G) OpenGL Reference fglRenderMode(3G)NOTES
If an error is generated, fglRenderMode returns 0 regardless of the
current render mode.
One particularly surprising error condition occurs when the selection or
feedback buffer is too large for the implementation to handle. The
problem might not be detected until fglRenderMode is executed, because
buffer memory might not be allocated or locked down until that time. In
such a case, it is possible that the only indication of the error is that
fglRenderMode will return zero. Thus it is especially important to check
the return value.
ERRORS
GL_INVALID_ENUM is generated if mode is not one of the three accepted
values.
GL_INVALID_OPERATION is generated if fglSelectBuffer is called while the
render mode is GL_SELECT, or if fglRenderMode is called with argument
GL_SELECT before fglSelectBuffer is called at least once.
GL_INVALID_OPERATION is generated if fglFeedbackBuffer is called while
the render mode is GL_FEEDBACK, or if fglRenderMode is called with
argument GL_FEEDBACK before fglFeedbackBuffer is called at least once.
GL_INVALID_OPERATION is generated if fglRenderMode is executed between
the execution of fglBegin and the corresponding execution of fglEnd.
ASSOCIATED GETS
fglGet with argument GL_RENDER_MODE
SEE ALSO
fglFeedbackBuffer, fglInitNames, fglLoadName, fglPassThrough,
fglPushName, fglSelectBuffer
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