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glTransformFeedbackVaryings — specify values to record in transform feedback buffers

C Specification

void glTransformFeedbackVaryings( GLuint program,
  GLsizei count,
  const char ** varyings,
  GLenum bufferMode);



The name of the target program object.


The number of varying variables used for transform feedback.


An array of count zero-terminated strings specifying the names of the varying variables to use for transform feedback.


Identifies the mode used to capture the varying variables when transform feedback is active. bufferMode must be GL_INTERLEAVED_ATTRIBS or GL_SEPARATE_ATTRIBS.


The names of the vertex shader outputs to be recorded in transform feedback mode are specified using glTransformFeedbackVaryings .Transform feedback records the values of the selected vertex shader outputs.

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:

  • Any variable name specified in the varyings array is not declared as an output in the vertex shader.

  • Any two entries in the varyings array specify the same varying variable.

  • 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.

  • 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.


GL_INVALID_VALUE is generated if program is not the name of a program object.

GL_INVALID_VALUE is generated if bufferMode is GL_SEPARATE_ATTRIBS and count is greater than the implementation-dependent limit GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS.


API Version Support

OpenGL ES API Version
Function Name 2.0 3.0 3.1
glTransformFeedbackVaryings -
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