Customizing Material Decal Response (UE5)

[@LookItsCollin]

Alex you are one of the best content creators for Unreal thank you for all your work.

[@TechArtAlex]

Thanks so much!

[@nicocluckers2467]

I've been trying to figure this out for a while. Thanks for explaining it so well!

[@TechArtAlex]

Glad it helped, thanks for watching!

[@SkemeKOS]

Thank you!

[@TechArtAlex]

Thanks for watching!

[@teratronwrx1]

Awesome!

[@TechArtAlex]

Thanks!

[@AlexQuick-s4m]

Very helpful video! Thank you I have been trying to use the DBuffer Color information as an opacity mask, but it doesn't seem to work. Do you know why this might be? Is it simply impossible to use that data for opacity? I had assumed it was just a set of color channels so it could be used as a generic "mask" but that doesn't seem to be the case.

[@TechArtAlex]

The dbuffer unfortunately cannot be used in any way that would alter the depth of a pixel or world position of a vertex, including changing opacity. It has to do with the order in which things are drawn. The decal is mapped into the mesh using world coordinates of a given pixel, but changing the opacity would reveal a different pixel with a different position. Basically it would be a circular dependency if it was allowed.

[@AlexQuick-s4m]

@@TechArtAlex unfortunate, but makes sense!

[@vaillecgart1854]

I have a question regarding the custom response. Is there a way to have this a custom material response, but only answering to specific type of decal ? As for now , the custom material response in the recieving material will treat any decal I project the way I set it up. But is there a way where a material could hanlde both , "regular" decal response, and, a custom decal response, depending if the decal type I use is set to be recognized as such ? I got something kind of working by storing an information like "If specular from projected decal is 0.51 instead of 0,5, use custom material response". This way on a surface, I can have two decals, behaving differently, but the limitations is that I cannot overlap these two without having values mixed up and artifact. I guess there is no way around, but I'm curious if you would know something that could help achieve this ? I hope the way I explained it is not too bad, anyway, thanks again for these amazing video ! :D

[@TechArtAlex]

Right, you would need to use one of the values (like specular) as an index to control which decal logic to apply. Overlapping gets tricky. There is only one dbuffer, so they are both writing their values to the same pixel. Either the top sorted decal wins entirely - or when using opacity, a resulting blend between the two (causing your encoded values to both be wrong). There are other ways of projecting "decals" you could use instead in some cases. For example, using the "StaticMeshDecal_Function" can imitate a decal projection using a translucent mesh. This doesn't use the dbuffer at all, allowing for a second layer. Translucent materials have their own limitations though. You may also be able to achieve something with dithering.

[@vaillecgart1854]

​@@TechArtAlex I forgot about this one ! Going to experiment it aswell. For now, I'm currently trying a "solution" via the metallic, with an IF any value above 0, then its special decal type "treatment". It seems to work, but it mean I cannot project any regular decal with metallic on the material recieiver, otherwise causing artifact like previously. But this way, I can overlap the "Special Decal" and regular decal, without issue. Anyway, thanks for your answer, Its really nice to share with you ! :D

[@TechArtAlex]

@@vaillecgart1854 Sure thing, thanks for watching!

[@qwetry-j2u]

Great feature! I was missing that in UE4. One question: does it work the same way with mesh decals too?

[@TechArtAlex]

I haven't tested it, but I doubt it. This is because I think they don't update the dbuffer until after opaque geometry is drawn, so it would be too late for the mesh to sample it. But I guess it couldn't hurt to give it a shot.

[@JieDu-yj2vd]

The receiver can decide whether or not to display the receiver's normal in decal, but only if decal's Normal slot can't connect anything or it won't work, but why

[@GatyhInteractive]

do you know if you can use normalWorldSpace with a dot product (0.0.1) to get the slope angle on a decal ? Cause i can't find a way to make it work !

[@TechArtAlex]

Yes, the decal will only output its general facing direction if you try to sample its normal. The decal can also sample the world position, which allows normals of the underlying surface to be calculated - however they will not be smooth. What in particular isn't working when you try?

[@Pullow]

Hi Alex. I've been trying to create a blood system that intereacts with surfaces - How can I make the decals control the surface blend of every material ? instead of going to every single surface material to apply this setup. Can't I control all of those effects in my Decal Material ?

[@TechArtAlex]

Your options will be very limited, since the decal material is not able to sample everything within the material it would need (such as a heightmap). This new workflow was designed to allow for that type of interaction, but with the downside of needing to be told how to interact on a per material basis. The best way to approach this is to use a master material / material instance workflow that contains the logic for how a particular decal should interact with something. This way each material instance can interact with it automatically, but with its own unique variables and textures.

[@Pullow]

@@TechArtAlex That's sad... Even the normals from the surface ? It seems I can't blend my decal normal with surface normals to achieve the "absorption" effect.

[@TechArtAlex]

@@Pullow Unfortunately. Last I checked, the decal materials can currently only sample the world position derived vertex normals, not the pixel normal. This can be used to mask the decal from appearing on surfaces that aren't properly aligned with it, which can prevent stretching artifacts - but probably not for detailed special effects.

[@Pullow]

@@TechArtAlex Alright then. Thank you, Alex

[@JieDu-yj2vd]

In UE, decal's three-plane projection of normals, other than what you do in your video, WorldAlignedNormal doesn't seem to work with patches that turn black

[@TechArtAlex]

You can get a reasonably correct tri-plane decal normals if you calculate them in world space. But what I show is probably the only way to get perfectly accurate tangent space normals.

[@AdnanSky-sm2xk]

great content. is there any way to use decal normal but still get the underlying mesh normal effect on the decal? i am trying to make a blood pool effect like the ones from last of us 2.

[@TechArtAlex]

Thanks! Yes, you can blend the dbuffer sample normal output and the base material normal and/or heightmap using any math you'd like using this technique.

[@DevilDaggersFan]

For some reason my decal's roughness parametr only works decal's perimeter, not entire decal. Why? LERP, where: A - Scalar parameter (decal's roughness) B - ORM Green Channel Alpha - DBuffer Alpha

[@DevilDaggersFan]

Normal Flatten works OK (using Dbuffer Colour)

[@TechArtAlex]

You'd have to unplug each channel and test combinations individually to see which is causing the roughness not to work.

[@JieDu-yj2vd]

I want to keep both, with decal's normals working at the same time as the receiver's normals, equivalent to mixing the normals of both

[@TechArtAlex]

Use the node "blend angle corrected normals" with the base normal going into input 1 and the decal buffer normal going into input 2.

[@JieDu-yj2vd]

@@TechArtAlex I tried it and it didn't work. If the normal in decal is used, then the receiver can't get the dbuffer.

[@JieDu-yj2vd]

@@TechArtAlexDecal's normal must remain disconnected to get buffer's normal.

[@TechArtAlex]

It works fine for me. Did you remember to disable the Normal in the Dbuffer response in the root node? It must be set to "None", or another option that omits normals (such as "Color, Rougness") otherwise the decal's normal will override the receiver's normals.

[@JieDu-yj2vd]

@@TechArtAlex Thank you so much. When I set None, it worked

[@indiependentgames9750]

my triplanar projection does not work, I have rechecked it a lot of times but it does not work for me, it shows me the correct image only on upper side, other sides gets stretched, any help/suggestions?...can I send an email I have also a couple of other questions...thanks if possible

[@TechArtAlex]

Sure, [e-mail]

[@indiependentgames9750]

thank you, I will write you soon with some screenshots to show you what happens, thanks!@@TechArtAlex

[@7WeirdSeeds]

why isn't everyone screaming about this?!

[@TechArtAlex]

It definitely slipped under the radar for most, despite having some really interesting applications. Thanks for watching!

[@LawsOnJoystick]

nice video, hey im applying a rain fx pack that works with decals to make splashes on surfaces etc, but it makes my models look low poly..instead of smooth, any ideas?Thanks

[@TechArtAlex]

Perhaps don't remove 100% of the normal map details when wet, but allow a blend with some variation in smoothness.

[@JieDu-yj2vd]

WorldAIignedNormal and WorIdAIignedTexture are not valid in decal, right?

[@TechArtAlex]

Right - those nodes rely on mesh vertex normals to control the projection blend, which the decal does not have access to. So you would need to create your own tri-planar functions that obtain normals in another way, like the scene sampler.

[@JieDu-yj2vd]

@@TechArtAlex I have watched your other videos on normal and decal, which are all problems that I have encountered but have not been able to solve. There is a problem of normal rotation, that is, when the Angle is 0.25, the direction of the normal line is wrong, which is no problem in other times, but I saw that in your test, there is no problem in rotation all the time. What is the reason?

[@JieDu-yj2vd]

@@TechArtAlex The texture used is the texture of the brick wall inside the bridge

[@TechArtAlex]

@@JieDu-yj2vd I couldn't say without being able to see how the material is set up. It can be helpful to go the the buffer visualization mode and select world normal so that you can observe how the vectors are changing to more easily detect flaws.

[@BEN3DVFX]

It still has problem in UE5.2, 5.3 & 5.4 If anyone finds a way, let me know, thanks

[@TechArtAlex]

What is the problem?

[@BEN3DVFX]

@@TechArtAlex studio.kzbin.info4aDBgiX9qgQ/edit

[@BEN3DVFX]

@@TechArtAlex kzbin.info/www/bejne/apKnc5qfjZ6knbM

[@BEN3DVFX]

@@TechArtAlex kzbin.info/www/bejne/apKnc5qfjZ6knbM

[@BEN3DVFX]

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[@andy80sdrums]

Your vocal frying makes following impossible. Sorry!

[@LudvikKoutnyArt]

I do not understand this. It makes no sense. If the decal response is defined on the material which receives the decal, not the decal material itself, then how do I make a surface which receives some blend decals and some modulate decals? For example, let's say I have a wooden table board, and I want to create oil stain decal, which multiplies oily color on top of the wood base color, but also paint stain decal, which doesn't multiply but blend the base color. With this new UE5 system, I can either have a material which receives blend decals, or one which receives modulate decals, but I can't have both. So I can't put multiple different decal types onto the single wooden desk board. 🫤

[@TechArtAlex]

You can, you just have to have the decal pass a value in an unused channel to inform the underlying material about what it is, so that it can alter its response accordingly. For example, for most decals you could just have it sample and blend the dbuffer without altering anything, but when a decal with special handling is applied it can be detected by a value encoded on the dbuffer and would follow the custom decal path.

[@TechArtAlex]

Take a look at my POM decal video, where I use dbuffer channels to pass general purpose data into the dbuffer, so that the base material can interpret it and decide how it wants to use it.

[@adamc3607]

How do you get DBuffer working in 5.2/5.3 only seems to work in 5.1? Never mind this was only a problem with material attributes not invididual inputs

[@TechArtAlex]

Thanks for watching, glad to hear you got it worked out.