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 had been 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 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:
glRenderModesets 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 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 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
glRenderModeis determined by the render mode at the timeglRenderModeis 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 glSelectBuffer and glFeedbackBuffer reference pages for more details concerning selection and feedback operation.