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color gradients animation: keep up length and velocity

Posted: Mon Apr 16, 2018 6:15 pm
by HHGG
I want to simulate a rotating circle with color gradients.
I've done this freehand with drag and drop of the outer little circle:

Image

But the problem is that the length of the color gradient is changing
a little bit during animation and also the velocity.

So is there a simple possibility to get an exact constant length of the
color gradient and an exact constant velocity for the animation?

Re: color gradients animation: keep up length and velocity

Posted: Mon Apr 16, 2018 6:32 pm
by synthsin75
Easiest way is to copy and paste the shape, move down the timeline, and rotate the handle all the way around to align with its duplicate's handle again. Then just set the first keyframe to linear interpolation and delete the duplicate.

Re: color gradients animation: keep up length and velocity

Posted: Mon Apr 16, 2018 8:42 pm
by will_f
It might help if your gradient control was centered in the circle. Also it looks like you used "smooth" interpolation on the keys for the rotation. Smooth interpolation starts and ends slow, and speeds up in the middle. Perhaps change the interpolation on those keys from smooth to linear.

Re: color gradients animation: keep up length and velocity

Posted: Wed Apr 18, 2018 12:25 am
by obtusity
Probably a silly question, but why not use a static gradient and a rotating circle?

Re: color gradients animation: keep up length and velocity

Posted: Sat Apr 21, 2018 2:01 am
by HHGG
Thank you for your tipp to use "linear". That is good enough for me, but thank for the tipp do use a duplicate.

Re: color gradients animation: keep up length and velocity

Posted: Sat Apr 21, 2018 2:16 am
by HHGG
obtusity wrote:Probably a silly question, but why not use a static gradient and a rotating circle?
I haven't think about that although it seems to be the obvious solution.
But do you or anybody know how to do that?

I think in the last frame I have do set the angle to 360 degrees.
And also set the direction of rotating to left or right.

With the form choosing tool I can't set degrees so I marked my object with
the point transform tool. Then there is a field where I can set the angle.
First problem: The angle is always set back to 0.
Second problem: There is no field to set a direction of the rotation.

So knows anybody how can I set in the last frame the angle to 360 degrees and the
rotation direction to left or right?

With the point transformation tool I can try a freehand 360 degree rotation
but I think I could do it more exactly if I only have to set the two values
I need in the last frame: angle and rotation direction.

But now I have a new thought: the color gradient has nothing to do with
rotating because the color gradient is simulating the shadows of a light on my object
and if the light position isn't changing and I rotate my object the color gradient
isn't changing. So the only possibilty is to change the color gradient directly.
Is that true?

But I see now you wrote about a static gradient. Is that a gradient that is rotating if the object
is rotating and where can I set a color gradient to static? I can't find such a setting.

Re: color gradients animation: keep up length and velocity

Posted: Sat Apr 21, 2018 2:32 am
by chucky
YOu could use a mask and have that unbound?