More control on Particles randomness

[matrem]

Operating system or device, Godot version, GPU Model and driver (if graphics related):

Issue description:

Only providing one scalar in [0, 1] in random fields, is a bit limitating (for example with particles).

I think random should not be clamped so we can get a random value around ( not clamped) the initial one .
Now we can only have a value between initial and 1 (with random to 1 or even a lesser range with random < 1).

Steps to reproduce:

Link to minimal example project:

[ghost]

randf() * N would give a random float from 0 to N

edit: not sure if that's what you mean

[matrem]

I mean something like that (for example on particle scale) :
https://github.com/matrem/godot/commit/02d0d698b1606246253027432431b02e01a6e4ed
So I can set my scale to X and then configure its randomness in [X-R, X+R] (instead of [X, 1]).

I know that we can do what we want converting the particles materials to shader material, but I think the default particles material should get basic users more possibilities.

[Chaosus]

The randf_range function is fixes this issue ? cc @akien-mga

[bojidar-bg]

@Chaosus this issue is about CpuParticles/ParticleMaterial, not the Random class.

[Chaosus]

Ah.. right

[Calinou]

Maybe the *_random properties could be changed to add/remove a random offset with the specified value. For example, if the *_random property was set to 1, the old behaviour could be restored by halving the property and setting the *_random property to the same value.

This means that if initial_velocity is 200 and initial_velocity_random is 50, it would have to be read as "200 ±50" (which is [150; 250]). Random values that exceed logically possible values (such as going below 0 for a property that only accepts values above 0) would likely have to be clamped.

This would break compatibility, so it will have to be done for 4.0.

[pwab]

I'll just link here to make it part of the discussion in the GIP:
godotengine/godot-proposals#815

[akien-mga]

Superseded by godotengine/godot-proposals#815.