Add support for normal maps, metallic-roughness maps, and emissive maps to clustered decals. #22039
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to clustered decals. This commit expands the number of textures associated with each clustered decal from 1 to 4. The additional 3 textures apply normal maps, metallic-roughness maps, and emissive maps respectively to the surfaces onto which decals are projected. Normal maps are combined using the [*Whiteout* blending method] from SIGGRAPH 2007. This approach was chosen because, subjectively, it appeared better than the more complex [*reoriented normal mapping* (RNM)] approach. Additionally, *Whiteout* normal map blending is commutative and associative, unlike RNM, which is a useful property for our decals, which are currently applied in an unspecified order. (The fact that the order in which our decals are applied is unspecified is unfortunate, but is a long-standing issue and should probably be fixed in a followup.) In particular, commutativity is desirable because otherwise one must specify which normal map is the *base* normal map and which normal map is the *detail* normal map, but that's not a policy decision that Bevy can unconditionally make, as decals aren't necessary more detailed than the base normal map. (For instance, consider a bullet hole decal embedded in a wall with a subtle rough texture; one might reasonably argue that the base material's normal map is the detail map and the bullet hole is the base map, even though the bullet hole's normal map comes from a decal.) Note that, with a custom material shader, it's possible for application code to use the decal images for arbitrary other purposes. For example, with a custom shader an application might use the metallic-roughness map as a clearcoat map instead if it has no need for a metallic-roughness map on a decal. And, of course, a custom material shader could adopt RNM blending for decals if it wishes. A new example, `clustered_decal_maps`, has been added. This example demonstrates the new maps by spawning clustered decals with maps randomly over time and projecting them onto a wall.
pcwalton
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Could you consider moving the assets to https://github.com/bevyengine/bevy_asset_files and loading them via the http asset loader? :) See https://github.com/bevyengine/bevy/blob/main/examples/asset/web_asset.rs
IceSentry
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Very minor nits.
The assets should be removed from the PR before merging and once they are available in the bevy_asset_file repo.
Other than that LGTM
alice-i-cecile
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I would really love a usage example focused on the use of this feature for mirrors, but won't insist that it goes in this PR :) |
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For maintainers: I'll retract my requested changes when the files are no longer in this PR, which is presumably when bevyengine/bevy_asset_files#6 is merged |
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@alice-i-cecile Did you mean for that comment to go in #13797? (I mistakenly linked this PR in Discord instead of that one when talking about mirrors) |
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This commit expands the number of textures associated with each clustered decal from 1 to 4. The additional 3 textures apply normal maps, metallic-roughness maps, and emissive maps respectively to the surfaces onto which decals are projected.
Normal maps are combined using the [Whiteout blending method] from SIGGRAPH 2007. This approach was chosen because, subjectively, it appeared better than the more complex [reoriented normal mapping (RNM)] approach. Additionally, Whiteout normal map blending is commutative and associative, unlike RNM, which is a useful property for our decals, which are currently applied in an unspecified order. (The fact that the order in which our decals are applied is unspecified is unfortunate, but is a long-standing issue and should probably be fixed in a followup.) In particular, commutativity is desirable because otherwise one must specify which normal map is the base normal map and which normal map is the detail normal map, but that's not a policy decision that Bevy can unconditionally make, as decals aren't necessary more detailed than the base normal map. (For instance, consider a bullet hole decal embedded in a wall with a subtle rough texture; one might reasonably argue that the base material's normal map is the detail map and the bullet hole is the base map, even though the bullet hole's normal map comes from a decal.)
Note that, with a custom material shader, it's possible for application code to use the decal images for arbitrary other purposes. For example, with a custom shader an application might use the metallic-roughness map as a clearcoat map instead if it has no need for a metallic-roughness map on a decal. And, of course, a custom material shader could adopt RNM blending for decals if it wishes.
A new example,
clustered_decal_maps, has been added. This example demonstrates the new maps by spawning clustered decals with maps randomly over time and projecting them onto a wall.