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Dithered LOD Transition on grass drops frame rate

I'm trying to improve frame rate by culling my grass. Checking "Dithered LOD Transition" in the grass's static mesh drops the frame rate.

Here, you can see it's high 30s (on the right) without Dithered LOD Transition.

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Now I check the Dithered LOD Transition.

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Now, you can see the grass is culled, and the frame rate has dropped to low 30s.

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You can even see the polys weren't in the map when the shaders were compiling.

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Why is this dropping frame rate? Is this a bug? How can grass be culled properly to improve fps?

Product Version: UE 4.17
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asked Sep 19 '17 at 07:46 AM in Using UE4

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Nerdballer Games
26 4 13 15

avatar image Nerdballer Games Sep 19 '17 at 07:58 AM

I forgot to mention, with no grass, the frame rate is in the 90s.

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2 answers: sort voted first

Found the solution. I stopped using dithering LOD transition as that wasn't helping. I went into the foliage settings and selected the proper foliage type.

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answered Oct 10 '17 at 01:21 PM

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Nerdballer Games
26 4 13 15

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Dithered LOD transition is expected to reduce framerate, because overdraw in transition regions is significantly increased.

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answered Sep 19 '17 at 10:08 AM

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Deathrey
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avatar image Nerdballer Games Sep 19 '17 at 04:17 PM

That's good but know, but then what's the solution?? What's the proper way to save frame rate by culling grass?

avatar image DP Studio Oct 10 '17 at 07:53 PM

Using proper LOD levels that minimise pop and triangle count, billboards, decreasing foliage density, layering multiple grass types that have their own separate cull distances.

To correctly enable 'per instance fade' https://i.gyazo.com/7e562e1a8f3604bb86bf2358719019ca.png https://i.gyazo.com/433006d24b7893691ce9bcd2186d8ea6.png

As you can see here, I have 2 foliage types, one that is shown at the distance that inherently has a small tris count and its density is set quite low as to look good at distance, while another that has more triangles but isn't rendered until the player is near it https://i.gyazo.com/a424ed3924fed50dbbf1051a195ccc3c.png

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