Define a speed via Spline Align tag

[chadiabo 0]

Hello

I am designing a dogfight between jets. I want to give my planes a path but also a pre-defined speed so I don't have to animate their position on the path, I found out to calculate the speed via position velocity, but I want to pre-define that speed without caring much about assigning keys on the position

If anyone has any ideas / plugins about planes flight rig I would be grateful 

Many thanks

 

 

[chadiabo 0]

Of course I need the given speed to be in Km/H unit :)

[jed 387]

I think this does it. There's a slider in kph, and it agrees with the XPresso position velocity

 

kilometers.c4d

 

you'll have to double check my math - I'm used to cm/frame not kph

[chadiabo 0]

Wow, thanks

I have to stick with a real plane dimensions, that's why it is in KpH

I think it works but I cannot find where I can input more than 500 kph, didn't find it inside the expressions. I will try to find out why

Many thanks

 

[chadiabo 0]

Found it, many thanks

[jed 387]

Position velocity is interesting because, if you hover your mouse over it, it shows as a vector. However, if that port is connected to a real input, XP does the 3D Pythagoras conversion for you ie

 

speed = sqrt(x^2 + y^2 + z^2)

[madmarvin 4]

Sorry for hijacking the thread, I really like this and want to know if it could be adjusted so that any given frame, while scrubbing the timeline, would show the correct position along the spline? Now you have to play from 0.

[jed 387]

@madmarvin you could use the same math to make a calculator in XPresso to get the 100% align frame value for a regular align to spline on a uniform spline, then enter this manually. The object would travel at the designated kph, and would scrub.

 

kphcalculate.c4d

 

the thing with the addition method for speed, is that it can be adjusted on the fly - for normal objects as well as align to spline. A helicopter blade, with the rotation done using addition, can be spun up and down - from stopped to max to stop again. When you get the helicopter blade speed by multiplying time (seconds or frame), it goes backwards when you try to slow it down.