Possible bug with velocity test and object bind

[insertmesh]

Hi there,

I have found a possible bug, although I´m thinking it might be intentional/user error:

I have particles bound to an objects surface and want them to break off, when the deforming object exceeds a certain speed.

So I have object bind set to "Lock to surface" with 100% friction and added a property test for velocity magnitude.
I can see with the display data, that the particles clearly exceed the specified velocity, yet they don´t test true.

But when I change the Position bind type from "sticky" to "Linear spring", it works.

Haven´t played around enough with the linear spring type and for what I´m doing it seems fine, just checking if thats intentional or a bug, since breaking off by velocity is quite a common scenario.

[tyFlow]

Object Bind in sticky mode works directly on particle positions, not velocities. That doesn't mean particles will have zero velocity....since other operators may still influence the velocity....but the changes Object Bind in that mode makes do not affect velocities.

You can use a Speed operator in continuous mode with both dropdowns set to 'verlet' to convert positional changes in the Object Bind to velocity data on the particle. Then put your test after that.

[insertmesh]

Yep, that worked, thanks for clearing that up!

Just in case anyone else encounters this...I still had problems getting it to work, particles kept testing true even after turning off every single op that could produce speed...until I realized that in the property test value I had put a variation of 0.1 and when the test value was below that, particles would mathematically test true, even if they had no velocity at all...doh...

[devailo]

Hello, not to start a new topic but i have a similar problem. I have moving objects and have some particles bound on them. I want new particles to start spawning when the objects stop moving. So i guess this is velocity magnitute equals 0 ? yes but it does not work. it either spawns particles all the time or no particles at all depending on the tests i do. Any suggestions?

https://i.imgur.com/dYMVspB.png

[tyFlow]

Please read above about using a Speed operator to assign proper velocities to your particles. Put that above your velocity test.

[devailo]

hi, sorry i forgot to write that i did try the verlet speed thing and it didnt work. Maybe im doing something wrong overall? as you can see in event 01 i am sticking red particles to the bricks but they are not visible, the green ones from the next event are . And they still generate when the bricks are moving and velocity magnitute is equal to 0 . I have made every other variable = 0 . and it still is this way.

https://i.imgur.com/4xhwlna.png

edit 1 : i checked the display data and it says velocity and velocity magnitute 0 for all particles.. somethings is not working right and i dont know if it is my mistake. Tried to do the same test with particles emitting from the emitter and it correctly get the velocity data and test. now when the particles are stuck on a bricks i says its zero. did the speed test thingy and still doesnt work

edit 2 : i had set the speed to 0 . now i set it to 0.1 and it started showing info about the particles. they finally have some value in their velocity magnitute. And when i set that i want to go to the next event by checking if the vel mag = 0 . it still starts from frame 0 to generate the particles. I tried telling it to start from frame 5 for example in order to skip the first frames where it is stationary but still to no avail.

also i try other types of tests to make it work but cannot . What i notice is the red particles dissapear most of the times when the green ones appear from the second event. and i havent ticked kill parent. why is that?