SolidParticleSystem "DepthSort"

Bugs
21

It works !!!

material.diffuseTexture = texture;
material.diffuseTexture.hasAlpha = true; // SOLUTION
material.alpha = 0.7;

do not use material.opacityTexture

22

@adam sorry man )

23

Sorry? For what?

24

Often distracted you )

25

No problem.

Iā€™m not sure how that fixes the issue, but glad you found a fix for your situation.

26

Following @jeromeā€™s link about meshes transparency you can find that there is alpha-tested and alpha-blended types of meshes.
Using diffuseTexture.hasAlpha = true instead of opacityTexture changes mesh from alpha blended to alpha tested.