This function will add 2D position data to the vertex currently being defined for the custom primitive. You supply the buffer to write the data into as well as the x and y position for drawing.
vertex_position(buffer, x, y);
|buffer||The buffer to write the information to.|
|x||The x position.|
|y||The y position.|
vertex_position(buff, x - 100, y - 125);
The above code will set the position of the vertex being defined.