glTransformFeedbackVaryings

glTransformFeedbackVaryings: man3/glTransformFeedbackVaryings.xml

The names of the vertex or geometry shader outputs to be recorded in transform feedback mode are specified using glTransformFeedbackVaryings. When a geometry shader is active, transform feedback records the values of selected geometry shader output variables from the emitted vertices. Otherwise, the values of the selected vertex shader outputs are recorded. The state set by glTranformFeedbackVaryings is stored and takes effect next time glLinkProgram is called on program. When glLinkProgram is called, program is linked so that the values of the specified varying variables for the vertices of each primitive generated by the GL are written to a single buffer object if bufferMode is GL_INTERLEAVED_ATTRIBS or multiple buffer objects if bufferMode is GL_SEPARATE_ATTRIBS. In addition to the errors generated by glTransformFeedbackVaryings, the program program will fail to link if:

1. The count specified by glTransformFeedbackVaryings is non-zero, but the program object has no vertex or geometry shader.
2. Any variable name specified in the varyings array is not declared as an output in the vertex shader (or the geometry shader, if active).
3. Any two entries in the varyings array specify the same varying variable.
4. The total number of components to capture in any varying variable in varyings is greater than the constant GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS and the buffer mode is GL_SEPARATE_ATTRIBS.
5. The total number of components to capture is greater than the constant GL_MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS and the buffer mode is GL_INTERLEAVED_ATTRIBS.

glGetTransformFeedbackVarying is available only if the GL version is 3.0 or greater.