get zero data from RGBCamera

[wzjscut]

          how about the raisim example `sensors`? Do you also see black images only?

Originally posted by @jhwangbo in #448 (comment)

I follow the answer above. I use the example file in https://github.com/raisimTech/raisimLib/blob/master/examples/src/server/sensors.cpp
and I use the API std::vector img = rgbCamera1->getImageBuffer(); to get data

but all the data i get is zero. why?

[jhwangbo]

Did you run raisimUnreal?

[wzjscut]

Did you run raisimUnreal?

I just run the raisimUnity. Does this API only run in raisimUnreal?

[wzjscut]

It do successfully get the image data in raisimUnreal