OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Floating-Point Pack and Unpack Functions

These functions do not operate component-wise, rather, as described in each case.

uint packUnorm2x16(vec2 v);uint packSnorm2x16(vec2 v);uint packUnorm4x8(vec4 v);uint packSnorm4x8(vec4 v);

First, converts each component of the normalized floating-point value v into 8- or 16-bit integer values. Then, the results are packed into the returned 32-bit unsigned integer. The conversion for component c of v to fixed point is done as follows:

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packUnorm2x16: round(clamp(c,  0, +1) * 65535.0)packSnorm2x16: round(clamp(c, -1, +1) * 32767.0)packUnorm4x8:  round(clamp(c,  0, +1) * 255.0)packSnorm4x8:  round(clamp(c, -1, +1) * 127.0)

The first component of the vector will be written to ...