I need to make a moving head follow a guitarist along the top of a bar, like a followspot. So far, to keep the thing on the right track, I've recorded intermediate following cues for his position on the bar along point a to point z. This seems like a fairly accurate way, but extra cues and extra programming time. Should I be looking into changing the path of the positions (in "path") to make it track more accurately with one single pair of A to B cues? Pretty basic question, but the bar is small and the heads are close to the guy and programming time is at a premium. I know, their lack of planning isn't my emergency...
From the sounds of it, something else that might work for you would be a IFCB Scene. Make the Scene your final position.
In your cue, you place the fixture in the first position on the bar. When he starts to move, you trigger the IFCB fader and slowly move it up, pausing when he does and continuing all the way to the second position.
The next cue in your stack would release the scene and keep the light where you need it.
Just a thought...I've used this method to "follow" people and it seems to work fairly well...your mileage may vary....
You could also make two cues in a cuelist and then change the cuelist option to manual fade. Now you can use the fader to manualy fade back and fourth inbetween the two cues.
Imagine Moving head is a few feet behind the path the "talent" walks. (See Examples below. 'o' are to fill space for editing. Yes I will use CAD next time.)
Theoretically, (in radial coordinates) A and B are same distance from light and have symmetrically opposite angles. What this means is that tilt at A and B are identical and Pan is the only parameter that would change from point A to B. However, we know that if we record position A and B then cross-fade, that the beam will swing way out from the line in a circular arc.
The solution for this and the way to make the light travel in a linear fashion on the line is to introduce a third location C which is on the line at a location directly in front of the light. Basically, you bisect the triangle between A B and the light. Then if you program a cue at point C, the head tracks the line to C and then the next cue tracks the line to point B.
I understand this is a complex explanation but this is the only effective way to track a line with any fixture but a a head specifically. Also note that this only works with one light tracking as the light reaching point C must be exactly perpendicular to the line you are tracking. You can however use multiple fixtures but remember that if proportionally the distance between the lights is small compared to the distance to the line and the distance to the walk path then the error goes down but if the distance from the light to the line is small and the distance between fixtures is great, you will see the arc movement instead of the linear line track.
[CENTER]oooooo X oooooo X oooooo ooooooo \oooooo/oooooooo oooooooo \oooo/ oooooooo ooooooooo \oo/ ooooooooo A-------------- \/ --------------B -- oo | oo -- -- C --[/CENTER]
As a solution, you can create subsequent points on the line respective to each lighting fixture that are perpendicular to each light. For example, if you have 4 lights that track the line, you have 4 points between A and B. Oh and for this kind of cue, I recommend building a cue-list (as a chase) that grabs the position only (or focus, zoom, Iris too depending). Make a guess on your timing, and then hold on to the Rate wheel when you run the cue. Don't forget to make "Brake" your path or else the aud will notice the stops.
[CENTER]oooooo X ooo X ooo X ooo X ooo X oooooo oooooo | ooo | ooo | ooo | ooo | oooooo oooooo | ooo | ooo | ooo | ooo | oooooo A-------1-----2-----3-----4-----5-------B[/CENTER]
I have done this with as many as a dozen lights, tracking a line 60' long and it took 13 cues and about a hour to build and test with the artist. It didn't look "Autopilot" smooth but it did look better than a "spot opp" smooth.
