Knoll Light Factory workflow???

[Darby Edelen]

I think it will be a little difficult to pull this off properly. Tracking the Lens Flare to the light source is probably the easiest part, I would recommend using a Null object and applying an expression to the Lens Flare’s source that links it to the Null’s position:


thisComp.layer("Null").position


Then if you can get a good motion track you can apply that to the Null, if not you’ll have to keyframe the Null’s position to match the source yourself. You won’t have to do this frame by frame, I suggest a keyframe every second to start, then go back and see where the flare moves off the source and make a new keyframe there, rinse, repeat.

As for hiding the flare when the light has disappeared you will probably need to adjust the Opacity of the layer that the Lens Flare is on manually.

Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA

[Patryk Rebisz]

I’m not sure i totaly understand you.

I insert a null object and then track the light source. Then apply the Track Motion data from the light source layer to the null object… right?

Then i add the expression:
thisComp.layer(“Null”).position

to… the light layer or null (and if so how do i add the expression)…???

[Patryk Rebisz]

What if i track another object in the frame and then apply taht track to the null. Then how do i format the expression to take the anchor point movement into concideration?

[Darby Edelen]

Is the light source coming from within AE or is it in source footage? If it’s within AE then you don’t need a Null as AE already has all the position data for the light. Let me know which case it is and I can further clarify.

Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA

[Patryk Rebisz]

Yes, it’s the footage. Right now i’m tracking portion of the fooatge (not the light source itself as it’s being obstructed from time to time) and apply the motion to the null, then i add the lens flare to the source footage but add that expression you told me about. So the flare gets it’s position from the null… Now if only i knew how to offset the null so that the light was not coming from where i was tracking the footage but from the actuall light source…

[Jacob Wessler]

Patryk,

I have found the follow solution to your tacking problem.

Track your object in your source footage and apply it to a null object.

On your flare layer, ALT-click the stopwatch for your lens flare center and apply the following expression

x = thisComp.layer(“Null”).position[0];
y = thisComp.layer(“Null”).position[1];
[x+30, y-60]

What this does is tell After Effects to make two variables, x and y, and to take the position data from your null for each of them (the [0] applies to the “x” data, the [1] applies to the “y” data, and [2] applies to “z” data).

The last line of the expression is how you get your offset. This will correct the distance between the oject that you tracked and the position that you want your lens flare. Of course, in your case, you’ll change the number (30 and 60) to whatever you need them to be. This take some trial and error, but once you get it, you’re golden.

As for times when an object passes in front of your light source, opacity would be a good way to hanlde this. Set a HOLD keyframe one frame BEFORE your light disappears and set its value at 100%. Advance one frame forward (page down key) and set another HOLD keyframe at 0%. Advance until your light source is visible again and set another HOLD keyframe. If you want your light to quickly fade out as it’s being obscured, set normal keyframes and place a little distance between them.

Good Luck,
Jacob

[Darby Edelen]

I would recommend redoing your motion tracker. If you’re not totally familiar with it, the tracked feature can be chosen independently of the attach point. The feature is what is actually used to track the motion, and the attach point is where that motion will be applied to the target layer, so set your feature to whatever is most easily tracked and your attach point to the location of the light.

Note that if the feature and doesn’t reside on the same plane in your footage as the light then the feature may move faster or slower than the light due to parallax, so choose your feature wisely.

The other option is tracking the light while it’s visible, and adding the keyframes where it’s not by hand.

Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA

[Darby Edelen]

[jwessler] ”
x = thisComp.layer(“Null”).position[0];
y = thisComp.layer(“Null”).position[1];
[x+30, y-60]”

This works as well if you want to guess at the numbers. A simpler one line version would be:

thisComp.layer("Null").position + [30, -60]

Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA

[Ty Audronis]

Correct me if I’m wrong, but if you parent the null that the flare is parented to, the lense reflections don’t change position accurately. I tried applying tracking from a null to the light source location via expression,( effect(” Light Factory”)(“Light Source Location”) = thisComp.layer(“Null 1”).transform.position; ). but appearantly that property is read only :(. How would I get the lense reflections to be at the right angles for the position with tracking?

Ty Audronis
Supervising Editor, California Academy of Sciences/Morrison Planetarium

[Ty Audronis]

Ok… kinda cludgy, but I got it…

First, track your point that you want the flare to be on
Next, create a shape layer with a tiny white dot on it
Apply the track to a null layer
parent the white dot to the null
Precomp this stuff

Then, in the main comp, when you apply knoll, use the precomp as the location layer, and you’re in like flint… all the optics stay realistic.

Hope this helps future googlers… as I couldn’t find this anywhere, and it took some digging just to find out what the hell the location layer is for…

I think I’ll do a tutorial on youtube for this.

Ty Audronis
Supervising Editor, California Academy of Sciences/Morrison Planetarium