[hzqst]

the best way to do player semiclip is to Rebuild pmove->physent array in pm_shared.c in server dll.
if you want traceline semiclip, you have to

give engine your pfnShouldCollide function:
pFunctionTable->pfnShouldCollide = gNewDLLFunctions.pfnShouldCollide;

in :
int GetNewDLLFunctions(NEW_DLL_FUNCTIONS *pFunctionTable, int *interfaceVersion)