You're right about fraw, it's limited. I think we
will also use curvefitting now so any more info
you could share on fraw2 tangets would be most appreaciated!
Alex.
----- Original Message -----
Sent: Friday, June 29, 2007 6:22 PM
Subject: RE: tangent computation in .fraw
/ .fraw2 ?
Alex,
I would suggest you use .fraw2 as I don't think .fraw can support
arbitrary tangents (i.e. length is fixed) because it is a very old file
format.
Anyway, here is how tangents are computed in .fraw from the single
slope value saved in the file:
For each key it reads time, value, leftslope,
rightslope
the right tangent of the *PREVIOUS* key is
computed like this:
tanX = (time -
previous_time) / 3.0
tanY =
previous_rightslope * tanX
SetRightTangent( previous_time, tanX, tanY )
the left tangent for the *CURRENT* key is computed
like this:
tanX = -tanX (i.e.
negative of value computed
above)
tanY = leftslope *
tanX
SetLeftTangent(
time, tanX, tanY )
then update the previous_time and previous_rightslope for the next
key etc.
Hope this helps.
--
Brent
From: owner-xsi(at)Softimage.COM
[mailto:owner-xsi(at)Softimage.COM] On Behalf Of Alexander
Hemery
Sent: Friday, June 29, 2007 2:30 PM
To:
XSI(at)Softimage.COM
Subject: Re: tangent computation in .fraw / .fraw2
?
Hiya
Sorry didn't come to work yesterday
...
In .fraw format, only one value is stored for
each tangent, so we assume that the length is actually derived from the
difference in the key-frame time values. I have all the curve & tangent
information that I need, and the
distance between the key-frames. You said that "Added tangent lengths on 2 successive keys
cannot be more than approx 1.25 of the distance between 2 keys ", do
you know the formula to compute the single value that .fraw needs
for each tangent, based on the information that I have?
p.s
Hopefully it will be cool yeah ...I've
always deeply enjoyed visuals synched to sound! From disney's fantasia to gantz graff video clip ...it all
rocks!
Would be nice to have something that helps you
explore that visual/sound perfect match ...although I'm realizing that using
waveforms won't get you very far. MIDI would be the way to go
afterall.
Anyhow I'll post a link soon for a beta version
anyone could try out and hopefully give some improvement
feedback.
Cheers!
Alex
----- Original Message -----
Sent: Wednesday, June 27, 2007 6:04
PM
Subject: Re: tangent computation in
.fraw / .fraw2 ?
Fraw and fraw2 simply store the tangents. Tangent syntax
requires 4 values per key (left length, left height, right length, right
height). Added tangent lengths on 2 successive keys cannot be more than
approx 1.25 of the distance between 2 keys and when you add a key on an
editor that is ensured by the software.
But thats too simple, you must
want something else.
You want to create tangents from raw key data?
The only way you can do that is doing some recursive fitting
algorithm.
Im not sure what you are after but making fcurves from
frequency sounds cool.
On 6/26/07, Alexander
Hemery <vortex(at)fhw.gr>
wrote:
nope..but thanks
-----
Original Message -----
Sent:
Tuesday, June 26, 2007 5:22 PM
Subject:
Re: tangent computation in .fraw / .fraw2 ?
Does the do what you are looking
for?
-----
Original Message -----
Sent:
Tuesday, June 26, 2007 9:47 AM
Subject:
tangent computation in .fraw / .fraw2 ?
Hello,
Anyone know how those tangent values in
.fraw/.fraw2 files are computed ?
We're doing a little application to get
fcurves from sound ..by using a selected frequency (not global
amplitude) ...but i can't understand what those tangent numbers derive
from ... Any ideas?
There's always the option of
exporting linear keys ...but what would be nice is to get a nice
bezier with as few keys as possible....
Cheers
--
Alexander Hemery
