Fix to render depth or depth/normal of waving grass

[Seongdae]

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Purpose of this PR

Fix to render depth of waving grass in depth prepass

• In opaque pass billboard offset was applied
• But, those offset wasn't added to depth and depth/normal prepass
• In case of billboard grass, the vertex result was not the same between opaque and prepasses

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Testing status

Add new terrain
Add detail billboard grass
Bush detail where you want to check

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Comments to reviewers

It wasn't working to draw depth of waving billboard grass to depth texture

[ellioman]

I'm not 100% sure what the bug is that this PR is trying to fix. Would be nice to get that info in the description.

With a PR that got introduced today, we now have a WavingGrassDepthNormalsPass.hlsl file with the DepthNormals passes, which also need to be looked at.

In the same PR, four test scenes were added in the Terrain Project to test depth & normals (Forward & Deferred). Can we expand on that and include some testing for this in order to avoid any breakages in the future?

[Seongdae]

@ellioman Thanks for letting me know about WavingGrassDepthNormalsPass.hlsl added, I updated and merged from master to my branch.

In case of detail checked as billboard, depth prepass of waving grass didn't work and I tried frame debugger to check if the prepass worked. the prepass was called but depth didn't appear in depth texture.(depth normal is also the same)

TerrainBillboardGrass(v.vertex, v.tangent.xy) was applied in opaque pass before but depth prepasses didn't have it.
So I added TerrainBillboardGrass(v.vertex, v.tangent.xy) to vertex stage of depth and depth/normal pass then the result appeared in the frame debugger and the those work well in screen space features(ambient occlusion and shadow)

here are the comparison

[before adding TerrainBillboardGrass(v.vertex, v.tangent.xy)]

[after adding TerrainBillboardGrass(v.vertex, v.tangent.xy)]

[phi-lira]

Adding @russoh for terrain review

[russoh]

I'll loop in terrain team for a review, would be good to have somebody from the team, look over this.

[spaceburp]

would it be possible to cover what Elvar brought up regarding tests?

In the same PR, four test scenes were added in the Terrain Project to test depth & normals (Forward & Deferred). Can we expand on that and include some testing for this in order to avoid any breakages in the future?

[russoh]

The changes logically look sane to me, but I agree with other sentiments that we should probably add a test that would fail an image comparison if those changes were subsequently stripped out again. Also, do we have any larger terrain + grass demos that can be used to validate against?

[phi-lira]

@Seongdae please ping reviewers for another look.

[Seongdae]

Should I handle the tests of terrain and does it allow me to add scenes for comparing with detail shadows?

[phi-lira]

@Seongdae yes, please add tests, ping @ellioman or @russoh for help.

[ellioman]

What's the status on this PR @Seongdae ?
Regarding the test discussion, there are now two tests scenes, in the Terrain Project, for DepthNormals that you can check and verify:

• 201_DepthNormalsDeferred
• 201_DepthNormalsForward

And then we also have two other test scenes for Depth, I believe 200.

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[Seongdae]

@ellioman this is to fix depth/normals of billboard grass, but there is no billboard grass in the test scenes you told me. Should I add billboard grass to the scenes?

[ellioman]

@ellioman this is to fix depth/normals of billboard grass, but there is no billboard grass in the test scenes you told me. Should I add billboard grass to the scenes?

@Seongdae
Yes, I think that's a good idea. Those scenes should be testing as much as possible Terrain related. So if you can structure the scene with the billboards as well, then that's perfect. 👍

[Seongdae]

Checked it in the terrain test scenes @ellioman told me, and also update the reference images now. I'm waiting for Yamato, but there seem to be an issues in the current test environment.

[Seongdae]

The tests related to Terrain were passed now.