Parsing object instance mask about unrealcv

[marioyc]

If I understood correctly the execution order is (probably with other things in the middle that I wasn't able to follow):

1. FCameraCommandHandler::GetObjectInstanceMask
2. FCommandDispatcher::Exec
3. FPlayerViewMode::Object
4. PaintObjects

and then PaintObjects calls FObjectPainter::Get().PaintRandomColors() which makes it seem like an object wouldn't have the same color across time.

[qiuwch]

Yes, the color is constant through time. See here. This code is a bit messy and needs to be cleaned up.

Getting colors for objects only needs to be executed once, so the speed does not matter much. Getting object mask needs to be executed every frame. All the performance bottleneck should be in here.

The execution order and the logic behind is: Every UnrealCV command will be executed by FCommandDispatcher. CommandDispatcher will decide which CommandHandler to use. For vget /camera/[id]/object_mask, the FCameraCommandHandler will be used. If this is still unclear, I can point to the specific location in the code. I should write a development page in unrealcv.github.io to document this.

PaintObjects happen when the game is initialized. PaintRandomColors means iterating over all objects in the scene and assign it a color. If the scene is the same (no object is deleted or added), the color will be the same, no matter running the game how many times. PaintRandomColors might not be a very good name.