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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 initial 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 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:

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.

Notes

If an error is generated, glRenderMode returns 0 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 executed between the execution of glBegin and the corresponding execution of glEnd.

Associated Gets

glGet with argument GL_RENDER_MODE

Tutorials

See Also

glFeedbackBuffer, glInitNames, glLoadName, glPassThrough, glPushName, glSelectBuffer

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