Name
gl.ArrayElement -- render a vertex using the specified vertex array element
Synopsis
gl.ArrayElement(i)
Function
gl.ArrayElement() commands are used within gl.Begin() / gl.End() pairs to specify vertex and attribute data for point, line, and polygon primitives. If #GL_VERTEX_ARRAY is enabled when gl.ArrayElement() is called, a single vertex is drawn, using vertex and attribute data taken from location i of the enabled arrays. If #GL_VERTEX_ARRAY is not enabled, no drawing occurs but the attributes corresponding to the enabled arrays are modified.

Use gl.ArrayElement() to construct primitives by indexing vertex data, rather than by streaming through arrays of data in first-to-last order. Because each call specifies only a single vertex, it is possible to explicitly specify per-primitive attributes such as a single normal for each triangle.

Changes made to array data between the execution of gl.Begin() and the corresponding execution of gl.End() may affect calls to gl.ArrayElement() that are made within the same gl.Begin() / gl.End() period in nonsequential ways. That is, a call to gl.ArrayElement() that precedes a change to array data may access the changed data, and a call that follows a change to array data may access original data.

gl.ArrayElement() is included in display lists. If gl.ArrayElement() is entered into a display list, the necessary array data (determined by the array pointers and enables) is also entered into the display list. Because the array pointers and enables are client-side state, their values affect display lists when the lists are created, not when the lists are executed.

Please consult an OpenGL reference manual for more information.

Inputs
i
specifies an index into the enabled vertex data arrays
Errors
#GL_INVALID_VALUE may be generated if i is negative.

#GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped.


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