Fix missing gamma correction in MPI mode
Fix missing gamma correction in MPI mode

MengjiaoH/ospray,MengjiaoH/ospray,wilsonCernWq/ospray,MengjiaoH/ospray,ospray/OSPRay,Twinklebear/OSPRay,MengjiaoH/ospray,ospray/OSPRay,wilsonCernWq/ospray,MengjiaoH/ospray,Twinklebear/OSPRay,Twinklebear/OSPRay,wilsonCernWq/ospray,Twinklebear/OSPRay,ospray/OSPRay,ospray/OSPRay