saving the final gather map in mental ray

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  01 January 2004
saving the final gather map in mental ray

I am rendering with final gather and using hdri also, i am not sure if that matters. I am also using maya5. Well i thought i just had to have the "final gather rebuild" box checked and put a name in the space for the file, then render it and it would save the file out. Then i was under the impresion, I just had to uncheck that same box and re render the scene, and i do have the same settings and all, just a new camera angle, and it would use the previous map from the last render.
Well i cant get it to do that, and when i go to look in the photons folder the file is not even there. any thoughts on what i am doing wrong?

  01 January 2004
there are 3 modes to store FGmap and also PhotoMap in Mental ray.

If you check Rebuild option, Mental ray will calculate Finalgathering every frame.

If you uncheck Rebuild, there are 2 way for MR.
MR will use a map stored that describe FG rays.
In the first way, MR will reuse your map and will add data, if needed. For exemple if you change your camera position ( it s your case ).
The second way, MR will just read the FGmap and do the render. To activate this in maya, the simplest way is Lock your FGmap file in Read-only. But you will get some artifacts due to fact you calculated the Fgmap for one angle.

So how to deal that ?
If you have a big render farm, you can rebuild at every frame.
If you have only one machine, so the best to do is to calculate some angle of your scene. In this way you build and accumulate Fg rays in your maps then you lock your FGmap and voila the render become fast for your scene without any flickering.
  01 January 2004
Thanks alot,

So to save my initial FG map, I uncheck the rebuild box and type a file name in the scpae, and then reder it? And after that is should find that file and use that information. Thanks alot for the help.

  02 February 2004
Quote: If you have only one machine, so the best to do is to calculate some angle of your scene.

Do you mean that you should render an angle that covers your entire scene? If so, would a render from a birds eye view be sufficent?
  02 February 2004
i never tested that. Why not, i will give a try.
With "some angle " i mean, do a orbit with your camera to get a maximum coverage.
Another trick is to calculate some frame ( 1x1 ) of your Camera path in reverse direction of the animation to accumalate Fgrays in your file.
  01 January 2006
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