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Miscellany: id Tech4 high-level objects are abstract classes, which will make the program look for virtual function address from the virtual function table at run time and cause performance problems. But there is a "trick" to avoid this problem. All objects are instantiated in a static way, as follows: idCommonLocal commonLocal; // Implementation idCommon * common = & commonLocal; // Interface manipulated in the code so that the compiler can determine at compile time the function is called, so as not to find virtual function table.