Store value from last frame and comparing it to current

JoakimMellergard

So I've been home sick for almost a week now and made this super overkill cigarette shader.

https://www.youtube.com/watch?v=uZOCA49TiFg

Everything is dynamic except for deciding whether the cigarette should "keep" it's ashes or not. I want to fix this by checking the cigarette's movement by storing it's position from last frame and comparing it to current. Any idea how to do this?

Rooster128

It'd probably have something to do with the tick event, and using a delta (not sure if blueprints uses delta or not- basically you want to check the time each tick takes in milliseconds, usually that's called tick length).

If you're problem is just storing the position value and saving it, I think what you could do is create a new variable in the blueprint called old_position or whatnot, change it to type vector, and at the end of every tick (after your logic for the ashes is done), set the old_position variable to it's current position.

Hope this makes sense! Sick shader btw- that looks very realistic!

JoakimMellergard

Rooster128 wrote: »

It'd probably have something to do with the tick event, and using a delta (not sure if blueprints uses delta or not- basically you want to check the time each tick takes in milliseconds, usually that's called tick length).

If you're problem is just storing the position value and saving it, I think what you could do is create a new variable in the blueprint called old_position or whatnot, change it to type vector, and at the end of every tick (after your logic for the ashes is done), set the old_position variable to it's current position.

Hope this makes sense! Sick shader btw- that looks very realistic!

Thanks! I'll certainly try this out.

I realised that I have another problem to take care of aswell.. I'll try to demonstrate:
As it is now:
The cigarette starts to burn - no movement. There will be ashes. The cigarette moves and the ashes disappear. The cigarette stops to move and ALL of the ashes will come back.
But I have a feeling it shouldn't be to hard to figure this out.

JoakimMellergard

Hmm I am having some trouble setting up your idea. Basically, what I want to do is this (written in pseudo code):

This also helps fixing the problem i mentioned in the other post.

oldPosition = vector3(0,0,0)
newPosition = vector3(0,0,0)
ashes = 1.0
burnAmount = the curve that defines how much of the cigarette that has burned
function Position:UpdateEveryFrame()
    newPosition = getPosition(cigarette)
    if(oldPosition == newPosition)
        oldPosition = newPosition
        ashes = ashes
    else
        oldPosition = newPosition
        ashes = burnAmount
 
end

and then I can use the ashes value to set the opacity

So do you know how I can make that script in nodes?