Decals are not supported for glb files

vijay_krishna · October 7, 2022, 11:34am

Hi,

We are trying apply decals on tshirts(.glb file) its not working. It seems only. babylon files are supported.
We are stuck from last few days… pls suggest the way forward

glb file used
https://raw.githubusercontent.com/myinzack/Riggedavatars/main/tshirt_walking.glb

Thanks
vijay

carolhmj · October 7, 2022, 12:09pm

Decals are supported for all types of imported meshes, including GLB, as you can see here: Available Mesh BoomBox | Babylon.js Playground (babylonjs.com). You should debug your code to ensure there are no mistakes.

Blake · October 7, 2022, 12:30pm

I think the issue is that decals aren’t supported for meshes with skeletons?

Also here’s the other thread on this topic for reference:

MarianG · October 7, 2022, 12:39pm

Hey, I think it is something related to decal size maybe.
gltf - https://playground.babylonjs.com/#1YTZAC#180
glb - https://playground.babylonjs.com/#8LFTCH#1453
even animated glb - https://playground.babylonjs.com/#ISZ7Y2#66

ps: I checked, … and maybe it is not related to decal size

I got some warnings when I want to create the decal
‘Setting vertex data kind ‘position’ with an empty array’
basicaly means we want to create the decal without ‘positions’. Close but still I don’t have a final answer why it is not working on your model.

carolhmj · October 7, 2022, 1:05pm

Hmmm, I think the decals can also go a bit under the mesh in case it’s deformed by skeletons. Like this case: Available Mesh BoomBox | Babylon.js Playground (babylonjs.com)

carolhmj · October 7, 2022, 1:08pm

I’ll take a deeper look into this example, thanks!

Blake · October 7, 2022, 1:37pm

It looks like if these two lines from CreateDecal were changed to be like below then the decal’s initial position and rotation could be computed accurately even if the mesh was deformed by skeleton or morphing. It might not make sense to do thou because the decal wont stay stuck to the mesh if it’s animated anyway, but if the animation is paused or stopped then it seems to work well (from my testing with the model in the OP)…

const positions = sourceMesh.getPositionData(true, true);
const normals = sourceMesh.getNormalsData(true, true);

github.com

BabylonJS/Babylon.js/blob/b0d22250dcdea276278f56a9719a58ff75e08aa2/packages/dev/core/src/Meshes/Builders/decalBuilder.ts#L32


      
          * @param options.position

          * @param options.normal

          * @param options.size

          * @param options.angle

          * @param options.captureUVS

          * @returns the decal mesh

          * @see https://doc.babylonjs.com/how_to/decals

          */

          export function CreateDecal(name: string, sourceMesh: AbstractMesh, options: { position?: Vector3; normal?: Vector3; size?: Vector3; angle?: number; captureUVS?: boolean }): Mesh {

             const indices = <IndicesArray>sourceMesh.getIndices();

             const positions = sourceMesh.getVerticesData(VertexBuffer.PositionKind);

             const normals = sourceMesh.getVerticesData(VertexBuffer.NormalKind);

             const uvs = sourceMesh.getVerticesData(VertexBuffer.UVKind);

             const position = options.position || Vector3.Zero();

             let normal = options.normal || Vector3.Up();

             const size = options.size || Vector3.One();

             const angle = options.angle || 0;

          

             // Getting correct rotation

             if (!normal) {

                 const target = new Vector3(0, 0, 1);

carolhmj · October 7, 2022, 1:47pm

Oh, checked here and that seems to do the trick! I think we could control this through an optional flag, something like applySkeletonsAndMorphs, as these functions are slower than getVerticesData. Want to do a PR?

Evgeni_Popov · October 7, 2022, 1:53pm

I’m not sure it’s the solution, as @Blake pointed out it won’t work when the mesh is animated (the decal won’t follow the animation).

It must be something specific to the model as @MarianG showed in https://playground.babylonjs.com/#ISZ7Y2#66 that decals can work even with animated models loaded from a glb file…

Blake · October 7, 2022, 2:21pm

EG if I pause the animation in that shark PG and rotate to check diff parts thou, I can see that the decals are wrong for many parts of the mesh because the skeleton isn’t applied…

Also the original PG had some other issues, I got it working by removing the predicates from the picking and passing the pickedMesh to CreateDecal. Here’s the PG I used for testing with the skeleton applied (it stops the animation when a mesh is picked to test that the decal is created properly).

IDK what the solution is for keeping the decal in sync with the animated mesh thou. The proposed changes would only help with paused/stopped skeleton animations and non-animated morphs I guess…

Blake · October 7, 2022, 3:55pm

Here’s a simpler PG to reproduce the warning “Setting vertex data kind ‘position’ with an empty array” with just a simple box mesh. If you comment out line 37 that disposes the old decal the error goes away. IDK what the issue with disposing them is.

EDIT: moved this part to a new bug report.

vijay_krishna · October 7, 2022, 5:22pm

Hi,
@Blake u r right if animation is stopped its working well…
i think decals does not support Rigged avatars. i tried with t-pose avatar its working
Need to find some workaround to apply for Rigged avatars.

Blake · October 7, 2022, 5:56pm

Hmm there’s an older thread discussing a work-around using a dynamic texture. They also ruled out using attachToBone() which I hoped might work for this. Maybe @ozRocker will have some more insights about it?

ozRocker · October 7, 2022, 10:27pm

I never had a proper Babylon.js solution for this. I’m still using a Python call to a compiled Blender module to bake the decal on the same UV map

Evgeni_Popov · October 8, 2022, 5:44pm

@Blake You’re right, I think the new (decal) mesh would need to have the matrix indices/weights filled correctly as well as using the same skeleton than the source mesh for decals to work correctly for rigged characters… I will try to have a deeper look about this issue.

Blake · October 8, 2022, 6:06pm

Oooh awesome, it would be amazing to support!

carolhmj · October 10, 2022, 11:07am

@Evgeni_Popov want me to create a Github issue to track progress?

Evgeni_Popov · October 10, 2022, 12:44pm

Yes, thanks!

carolhmj · October 10, 2022, 1:30pm

Support skinned/skeleton meshes on decals · Issue #13084 · BabylonJS/Babylon.js (github.com)

vijay_krishna · October 11, 2022, 1:18pm

Thanks @Evgeni_Popov for the support

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Decals are not supported for glb files

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