Final Gathering Map Reculculated!

[EdHarriss]

When fgmap rebuid is off, mental ray will open the file and load the fg samples in that file, the loading process should be much faster than fg pre-render process ( computing the map ). During the rendering ( raytracing), if mental ray determines more Fg samples are needed, it will cast it at the end of the render. Then it will add that to the fgmap (which contains what was loaded + the extra samples) In the render process, it really looks like it it computing, but it is loading the file.

Under the "Logged messages" section of the render options, turn on "Progress Reports" This way you will be able to tell if the FG map is being recreated or just added to.

If your render times are still too slow, consider baking your FG with rendermap. Then turn FG off. The scene will look the same but it will render much faster.

You are using 1 machine to render. If not, then that is your problem. FG maps can not be shared by 2 machines.

Are you using an HDR image to create the FG? If so, consider using a smaller version of the same image or using the Get>Light>Light Rig From Image instead. Both solutions will improve your rendertimes.

[tempor_3d]

Thanks for your reply !
Now let me underline the whole idea about calculation of the Final Gathering Map.

1. If the option is checked on then the map is going to be recalculated every signgle frame.
2. If the check box is checked out the Final Gathering Map will be calculated only during first time rendering. That mean that if there are animated object in the scene their animation is not going to be taken into account of Final Gathering effect. As a result there will be kinda "artifacts". When we say "animation" we mean everything:; from skeleton, lattice deformation to simples translation, rotation, scaling animation.
This fact makes it forthless option if you are going to render ANY animation! Then I just don't understand in which accasion that could be used...i mean when you want to uncheck that option? In case if you render the same frame number of times? when you change the texture on some of the obejcts? or tweak some map?
3. In case if you need to render the ANIMATED scene you want to check that check boc CHECKED. By other words - you want to recalculate the map every frame. But I've heard that has some problems. Because the algorithm calculated the FG map at every frame from random point in 3d space. That means that at every frame the FG map is not going to be exactly the same! Even if there are no animated elements in the scene. That unavoidably results to some kinda flickering during playback of the rendered sequence. (you could mimimize the flickering by dialing up the acccuracy settings as weell as min/max radious. But that will bring machine to the long rendering time).
If I've got something wrong please let me know.
Once again thanks for you help

[EdHarriss]

When you do not recalculate the FG map and the camera moves, mental ray only calculates the parts of the scene that were not visible during the previous frames. It takes those new calculations and adds them to the old FG map. This is much faster than calculating a new FG map for every frame.

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