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DylanM

Some further info on the shadow settings from LM

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A couple things to bear in mind about the changes to shadow settings:

- In v2.0 and v2.1 there was one shadow cast/draw distance which was tucked away in the Prepar3D.cfg. I believe it ranged from 3km to 12km, though I'm not sure of the exact number.

- Shadow cascade count was also tucked away in the cfg and ranged from 3 to 12 cascades. (each one is 2048x2048 rendering of a portion of the scene from the perspective of the sun, which is why shadows can be so hard on the GPU). Autogen and most scenery objects you would care about are within 12km of the camera anyway so there wasn't much point in going beyond that, but it did make terrain shadows less usable at high altitudes where you might want to see them far off in the distance.

- Cloud shadows similarly aren't very usable if you limit them to 12km (and that was the distance for ultra), so we added more options.

- If you set cloud draw distance higher than 0 you are turning on cloud shadow cast which was not available in v2.0 and 2.1

- If you set terrain cast distance above zero, you are turning on terrain shadow casting which you really need a beefy GPU to handle. If you set terrain draw distance above 10km, you are now drawing the terrain into the shadow maps out to much greater distances than were allowed in v2.1 without manually tweaking values in the cfg.

- On many of the GPUs we tested, large cloud cast distances were not nearly has hard on the GPU as large terrain cast distances, so we created two separate sliders to help users tune the GPU workload for shadows.

- We've always said terrain shadow casting is expensive, and with even larger draw distances, it is that much more expensive.

 

So to summarize, if you want to do a relatively fair performance comparison to 2.1:

- Set cloud cast distance to 0

- Set terrain cast to 0 if you had casting off in 2.1 and don't ever set it above 10km

 

 

Beau Hollis

Rendering System Lead - Prepar3D® Team

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Interesting. I wonder if they might consider adding back the non-realtime (FSX) terrain shadowing system in P3D. Those were calculated by the CPU and only updated once in a while – you can see the shadows being re-calculated if you change the time of day by a few minutes at dusk or dawn.

 

Realtime shadows are indeed extremely expensive, and not really needed for the actual terraain. The move too slowly over time.

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This is excellent foresight from the LM team.  Sure, it is expensive now, but end of this year/and next year onward - all the new hardware will be able to start taking advantage of these features.

 

I have Terrian Cast Distance set to 0, and still the Sim is amazing and I am running with 6970 Eyefinity (I can't wait for the P3D crossfire features in the upcoming revisions).

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For now I have set both sliders to the first notch along which is fine for GA flying and looks fantastic.

When I get time for an A320 flight I will fine tune.

 

To Beau and the rest of the LM team, congratulations on a fine update, you guys rock! :)

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Yup. You definitely want to be careful with these 2 settings. Pushing them to the right might lead to a stroke for your gpu! I made that mistake and my 6950 had a glimpse of the future...... And it wasn't in it!

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Last comment killed me :lol:

 

It is amazing how transparent the team is with sharing the nitty gritty on the work they're doing - is really is a such a fundamental change from what we were used to in the past.

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I have terrain cast on and cloud shadows too, both at 10.000. Shadows quality at Low. I don't really notice a difference in performance. I have fps locked at 34: maybe I would notice a difference if I used inlimited fps. But on my humble PC those two options certainly aren't the killers everyone seems to be talking about.

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