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[Manta] Re: Re: Re: Re: transactions in manta - setting camera


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  • From: Carson Brownlee < >
  • To:
  • Subject: [Manta] Re: Re: Re: Re: transactions in manta - setting camera
  • Date: Tue, 9 Dec 2008 16:20:22 -0700
That would be an interesting system but it seems like if you had to make all of those functions private and callable from a friended transactions class it would be adding a lot to code complexity and unnecessary if just creating a scene. If I'm understanding what you're saying right I'm not sure it would work if it requires putting calls into their own transactions, as you need to do a lot of calls in serial. You could just do something at runtime that checks if the system is rendering and spits out a warning to the user that their code is bad, but that would require keeping track of or passing in a manta_interface* to everything and unnecessary branching.
Carson


On Dec 9, 2008, at 3:49 PM, Roni Choudhury wrote:

I mentioned something like this a while back after it bit me in the donkey. I thought it would be good to somehow make these functions "transaction-safe only" by doing something clever with private/ protected subclassing from a function-object type and then use friendliness to ensure that they can only be used from certain places, but I guess it would be a major overhaul to do that.

roni

J. Davison de St. Germain wrote:
Why does setBasicCameraData() exist (or at least why is it visible) if it 'really' shouldn't be used? If it is necessary, perhaps it should be renamed to "setBasicCameraData_notThreadSafe()" or some such?
 Thanks,
       Dav
Carson Brownlee wrote:
the difference is that the transaction will be called when manta isn't rendering. the transaction is "safer" incase you have a shader that is referencing camera data in parallel to the gui code setting it. This is unlikely but possible, all calls like that should be done in a transaction. It wouldn't be a major loss in this case though as memory isn't being remapped, I don't think setBasicCameraData deletes the old cameraData.
Carson


On Dec 9, 2008, at 3:37 PM, J. Davison de St. Germain wrote:

Hi,

What is the difference between:

 data = manta_new(BasicCameraData(eye,lookat,up,fov,fov))
 engine.getCamera(0).setBasicCameraData(data)

And creating a transaction to do the same thing?

 Thanks,
       Dav



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