GPU Pro 5

294 IV Mobile Devices

glVertexAttribPointer ( ATTRIBUTE_STREAM_0 ,...)

glEnableTransformFeedback ()

glDrawArrays (...)

glDisableTransformFeedback()

swap ( vbo [0] , vbo [1])

i = i + k

This technique requires multiple versions of the shader where each version exe-

cutes the summation on incrementally more input attributes up until the maxi-

mum batch size. It is important to note that the maximum number of input at-

tributes available is limited by the API. This value (which must be at least 16) can

be retrieved by querying

glGetIntegerv with the argument GL_MAX_VERTEX_ATTRIBS.

4.4.3 Results

While gathering the data for the graph in Figure 4.3, a maximum