set start of multiple channels to 0 in chops

[Fomal]

Hi,

I have some point information in chops. I'd like all the curves to start from 0. At this point they start over a range from zero to one. So i'm looking for an expression that basically sais:

if the start of the channel is more than one, subtract that value from the channel, otherwise leave 0.

Hope anyone can help. Just bought the chops book but can't figure this one out.

Cheers Coen

[andrewlowell]

In the expression CHOP, type this: if($I == 0,0,$V)

If you just want to set any arbitrary channel etc to zero in the expression CHOP, type

So, whatever I would think just make the expression CHOP evaluate to zero according to your specifications if I understand your question correctly.

Hi,

I have some point information in chops. I'd like all the curves to start from 0. At this point they start over a range from zero to one. So i'm looking for an expression that basically sais:

if the start of the channel is more than one, subtract that value from the channel, otherwise leave 0.

Hope anyone can help. Just bought the chops book but can't figure this one out.

Cheers Coen

[Fomal]

Hi andrew,

Thanks for your fast reply. I made a quick image to illustrate the problem. As you can see, some curves start not on a value of zero. I'd like to shift these curves so they all have zero as their original start at their current Index (for example. Channel 40 has a start value of 0.5 at frame 23. This needs to be: start value of 0 at frame 23.

I'd normally do this with a math chop but there are many generated curves. I tried your expression but it didn't work. Filled both in but zero gives me zero for all curves and the other one made no difference at all.

Previously I made this example using a similar technique i'm trying right now. The only difference is is that the particle emission is not form a grid but a cube like shape. That makes my position channels offset a little bit (use the y direction for chops). So that's what i need to correct

Hope this extra info is what you need.

Cheers Coen

Edited July 22, 2008 by Fomal

[andrewlowell]

Ah now I see ... ok, the thing to do then is to split this operation off into two paths.

Use an expression CHOP set to

ic(0,$C,0) ... this will give the first sample through the entire channel range.

Then use this value to subtract from your channels; should give the correct offset. You could probably put it all in one expression CHOP like this:

$V - ic(0,$C,0)

Hi andrew,

Thanks for your fast reply. I made a quick image to illustrate the problem. As you can see, some curves start not on a value of zero. I'd like to shift these curves so they all have zero as their original start at their current Index (for example. Channel 40 has a start value of 0.5 at frame 23. This needs to be: start value of 0 at frame 23.

I'd normally do this with a math chop but there are many generated curves. I tried your expression but it didn't work. Filled both in but zero gives me zero for all curves and the other one made no difference at all.

Previously I made this example using a similar technique i'm trying right now. The only difference is is that the particle emission is not form a grid but a cube like shape. That makes my position channels offset a little bit (use the y direction for chops). So that's what i need to correct

Hope this extra info is what you need.

Cheers Coen

[Fomal]

Hi andrew,

That works great! I'll test tonight if it does what i expect it to do

Just one question:

with your expression you're saying: calculate the distance of the incoming channel to zero and substract this from it's total value. But why exactly does "ic(0,$C,0)" give you the first sample of the entire range? Checked the help of the expression chop but didn't make things any more clear

But again... Thanks!

edit: sorry, my fault. Read over it: It checks the input and looks for the realitve channel at index 0. All i needed to know...

Edited July 23, 2008 by Fomal