MeshParticleEmitter Weirdness

ncr · May 1, 2025, 10:42pm

Hola,

Not sure if I am using this wrong, but I thought the point of the MeshParticleEmitter was to emit only from the faces of the mesh. It seems to also be emitting from the empty spaces, between the mesh, is this expected behavior?

ncr · May 1, 2025, 10:52pm

Also, just out of curiosity of reading the implementation, is this code doing a random barycentric coordinate generation? So ideally, the resulting point will be a random point anywhere on a random face, and not just the vertices?

github.com/BabylonJS/Babylon.js

packages/dev/core/src/Particles/EmitterTypes/meshParticleEmitter.ts

7aee9a791


      
          import type { IndicesArray, Nullable, FloatArray } from "../../types";

          import { VertexBuffer } from "../../Buffers/buffer";

          import type { Scene } from "../../scene";

          import type { AbstractMesh } from "../../Meshes/abstractMesh";

          import type { UniformBufferEffectCommonAccessor } from "../../Materials/uniformBufferEffectCommonAccessor";

          import type { UniformBuffer } from "../../Materials/uniformBuffer";

          /**

           * Particle emitter emitting particles from the inside of a box.

           * It emits the particles randomly between 2 given directions.

           */

          export class MeshParticleEmitter implements IParticleEmitterType {

              private _indices: Nullable<IndicesArray> = null;

              private _positions: Nullable<FloatArray> = null;

              private _normals: Nullable<FloatArray> = null;

              private _storedNormal = Vector3.Zero();

              private _mesh: Nullable<AbstractMesh> = null;

          

              /**

               * Random direction of each particle after it has been emitted, between direction1 and direction2 vectors.

               */

              public direction1 = new Vector3(0, 1.0, 0);

Deltakosh · May 2, 2025, 3:22pm

This is correct, we emit from the faces not the vertices

ncr · May 2, 2025, 3:28pm

Ok, so it expected behavior in my original PG? It looks like points are emitting from empty spaces – spots that aren’t faces…

Deltakosh · May 2, 2025, 3:34pm

Hum no this is suspicious
Let me double check that

Deltakosh · May 2, 2025, 3:57pm

That was a nasty one!
Fix MeshparticleEmitter bug by deltakosh · Pull Request #16554 · BabylonJS/Babylon.js

Thanks a lot for the report!

ncr · May 2, 2025, 4:42pm

Heck yeah! Thanks so much!

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MeshParticleEmitter Weirdness

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