OpenGL unit vs natural measuring

Is there any algorithm/formula that can help me to figure out natural dim开发者_如何学运维ensions of a drawn object on OpenGL scene by using orthogonal projection. ? For examle: 3 Units = 3milimeters.

Thank you in advance.

The units can be anything and different people will have a different design approach. Some will definitely use metric while others use imperial units, and on top of that there will be many arbitrary ones. You just have to guess from each application separately, what they might be using.

Ask the operating system for its copy of your monitor's EDID information. That should contain the display width and height in centimeters.