# Very high ShadowDepths cost with CSM despite aggressive shadow optimization (UE 5.5.4)

**URL:** <https://forums.unrealengine.com/t/very-high-shadowdepths-cost-with-csm-despite-aggressive-shadow-optimization-ue-5-5-4/2735050>\
**Category:** Rendering\
**Tags:** Optimization, unreal-engine, Blueprint, question\
**Created:** [July 11, 2026, 5:21pm UTC](https://forums.unrealengine.com/t/very-high-shadowdepths-cost-with-csm-despite-aggressive-shadow-optimization-ue-5-5-4/2735050 "2026-07-11T17:21:30Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![BioFrost.in](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@BioFrost.in](https://forums.unrealengine.com/u/BioFrost.in)\
**Post date:** [July 11, 2026, 5:21pm UTC](https://forums.unrealengine.com/t/very-high-shadowdepths-cost-with-csm-despite-aggressive-shadow-optimization-ue-5-5-4/2735050/1 "2026-07-11T17:21:30Z")

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Hi everyone,

I’m trying to track down an unusually high **ShadowDepths** cost in UE 5.5.4 and I’m running out of ideas.

My project is an open world using:

- Unreal Engine 5.5.4
- Cascaded Shadow Maps (NOT Virtual Shadow Maps)
- Lumen disabled
- One Movable Directional Light (Ultra Dynamic Sky)
- Nanite enabled on some of static meshes
- World Partition

I’ve already tried the following:

- Reduced Dynamic Shadow Distance to a very low value.
- Reduced the number of cascades.
- Lowered shadow resolution.
- Disabled WPO/PDO on foliage where possible.
- Verified that only one Directional Light exists.
- Tested with Far Shadow disabled.
- Optimized foliage materials.
- Tested with foliage hidden.
- Tested different shadow settings.

Despite all this, **ShadowDepths consistently costs around 8-10 ms** , while the rest of the frame looks fairly reasonable.

Typical GPU timings:

```auto

```

```auto
ShadowDepths ~8-10 ms
Nanite VisBuffer ~3-4 ms
BasePass ~2-3 ms
PrePass ~1-2 ms

```

What confuses me is that lowering shadow quality often just shifts GPU time into another pass instead of significantly reducing total frame time.

I also noticed that disabling landscape shadow casting removes almost all visible shadows, which suggests the landscape is heavily involved in the shadow pass, but I wouldn’t expect such a high ShadowDepths cost with the current settings.

Has anyone experienced something similar in UE 5.5?

Is there anything specific that commonly causes ShadowDepths to remain this expensive even after reducing:

- Shadow distance
- Cascade count
- Shadow resolution
- WPO/PDO
- Foliage shadow complexity

At this point I’m wondering if this is related to Landscape, World Partition, or perhaps a regression in UE 5.5’s shadow rendering.

Any ideas or profiling suggestions would be greatly appreciated.

Thanks!

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<div class="post-metadata">

**Author:** ![Arkiras](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/arkiras/32/1008648_2.png) [@Arkiras](https://forums.unrealengine.com/u/Arkiras)\
**Post date:** [July 12, 2026, 2:08am UTC](https://forums.unrealengine.com/t/very-high-shadowdepths-cost-with-csm-despite-aggressive-shadow-optimization-ue-5-5-4/2735050/2 "2026-07-12T02:08:06Z")

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I don’t have a solution, but in my experience this is an issue specific to using regular Shadowmaps with Nanite. Simple way to test is to just disable it with `r.Nanite 0` and see if it improves.

My test scene (in 5.8) has abysmal performance when trying to use Nanite + Shadowmaps:

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/d/f/e/dfeb5bf2a2df08b232dbfe4890c98a62a4ebdac8.png)

Same scene/camera with `r.Nanite 0`:

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/6/2/7623b4f28e575b963d3899b2ec7dfbcae217ed57.png)

Unfortunately I don’t know of any way to fix it other than either disabling Nanite, or using a different shadow method.