Tuesday, January 24, 2012

72 – WTF LOD case study, part two

Welcome back to part number two!

Let's see what we get if we use LOD switching with my traditional technique from top down view of a quarter map with 22500 chests:

Memory consumption of  85 MiB with 18 FPS. Of course we will get small fluctuation as we scroll around and zooming can have dramatic effect. Still a huge improvement upon no LOD switching. Here is a completely zoomed out view:

Memory use of 29 MiBs, but only 6 FPS. Here is a first person view:

As you can see, there is some gain but not so drastic as with top down.

Now using the new LOD system, we get these results:

Memory consumption has gone down a lot but the FPS barely feels it. With this item density and this weak computer I could work actual miracles and the FPS won't improve that much. I shouldn't give away all my secrets, but here it is:

So after the practical experience of playing around with the new LOD in motion and getting a feel for the distances, I recreate some of the low detail meshes and create four performance profiles. Some of the new meshes are not quite as low as they could be. Rather than getting the best ugly performance available, I instead made sure that things still look good and if performance is not enough, you'll have to use a lower profile. Now, using a good computer, the "high" performance profile and adding back some color we get this:

"Medium" profile:

"Low" profile:

You may be wondering: "These look identical. What gives?". Well as static images there is not a lot of difference. In motion on the other hand, the level of the quality profile controls how much pop-in you will experience. And as object density gets lower, pop-in becomes more and more noticeable because you don't have as many object obstructing you visual path. On "high", pop-in is barely noticeable if you walk at a specific angle relative the bright side of the map.

But what about the fourth quality? Well this one is called "Ultra" and it will burn you up! Well, actually it is still quite tame and far from having zero LOD switching, but it is a huge step up from high both in quality and system requirements. I for one will be using Ultra because my laptop can handle it:

But what about top down mode. Unfortunately, the new LOD switcher does not like top down mode. It is designed for first person. But as you saw in the last post, top down mode is a lot faster, so I'll keep the old LOD switcher for top down and the new one for first person.

The quality profiles are not set in stone yet and I may adjust them. I also need to do intensive CPU profiling to make sure that the new LOD switcher does not over strain the CPU.

But most importantly, I need to get the chest textured and see if it still looks good with the new LOD switcher. UV mapping! This is going to be painful! And ugly!

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