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View Full Version : Motion Options: "Point At Target" disabled for Bank



jeric_synergy
11-13-2011, 04:47 PM
I'm constructing a little contraption, and I'd like to use the "POINT AT TARGET" per channel option in the Motion Options (the ones in the Rotation tab, not just the "Target Object" feature).

While you can set Heading and Pitch to "Point At Target", that option is ghosted for Bank. (Of course it is, that's the one I want to use. :devil: )

1) Why would this be so?

2) I'd prefer NOT to have to spin this object around to use one of the other axes: is there a way to just use Bank?

cagey5
11-13-2011, 05:01 PM
Applying those properties to a pencil with the aim being to point the pencil at the target. I would rotate the heading and adjust the pitch. I don't see how rotating it on its banking would help align it to the target.

But I'm probably missing something, it's getting late here.

jeric_synergy
11-13-2011, 05:41 PM
This isn't a question of pointing the HEADING axis at a target: I want to point the BANK axis, and only the Bank axis, at a target. It happens that with this object, the Bank axis is the most convenient. To use other axes would make the object a lot more difficult to deal with in Modeler.

Essentially, the situation is a crank: I want the 'connecting rod' to target a null, using the null as a pivot point halfway along the rod. As the crank rotates around, its child the connecting rod ignores the cranks rotation, ie. doesn't inherit the rotation, but is still moved in space. The rod continues to point at the null. IRL, the rod would slide thru the null point, which would be a pivoting sleeve joint.

Celshader
11-13-2011, 05:45 PM
2) I'd prefer NOT to have to spin this object around to use one of the other axes: is there a way to just use Bank?

Here's how you get a Bank channel to target an item:


In the Motion options, set the Pole item to what you would like the Bank channel to target.
Set the Bank Controller in the Rotation tab to "Align to Pole."


The arrow on the blue ring representing the Bank channel will now point at the Pole item.

jeric_synergy
11-13-2011, 07:20 PM
Jen, thanks, I'll try that. (I considered that for a second, then remembered I really don't understand what Pole does.)

FWIW, I also tried to use IK..... and just now figured out why that wouldn't work. ---Sometimes I require/force myself to spend an hour trying to figure it out before going back and looking at William Vaughn's videos. >;^)

ED: I'm guessing that, for BANK, "Point at Target" is never enabled, right?

Greenlaw
11-13-2011, 08:14 PM
Alternatively, you could just parent the object to a null, rotate the object 90 or -90 degrees on heading, whichever is appropriate, and then just use aim for the pitch of the parent null as your 'bank'.

G.

jeric_synergy
11-13-2011, 11:22 PM
Greenlaw: the reasons I didn't want to do that are:

1) This is a thing that exists within a picture frame, a bunch of cogs and linkages, and so far I've been able to build everything in Modeler just as it sits in Layout, and I didn't want to have ONE item that was 90 off from everything else;

2) I figured there was some way to do this (Hat tip to Jen), but if there wasn't;

3) ...it would be a good feature request. The other two rotational axes have "Point At Target", and IMO it would be a simple thing and add to UI consistency if Bank had it too. (Why not? I know that for 'normal', ie vehicular, targeting Bank doesn't make much sense, but the object isn't to handcuff the user to the preconceptions of the programmers, it's to devise a maximally flexible tool.) It may be that mathematically you can only have a maximum of two axes set to "Point At Target", but OK, we can live w/that, just add Bank.

Celshader
11-14-2011, 09:12 AM
he other two rotational axes have "Point At Target", and IMO it would be a simple thing and add to UI consistency if Bank had it too.

I have not tested this yet, but I see that Heading and Pitch also have "Align to Pole" options, just like Bank. Maybe Align to Pole is targeting under another name/algorithm.

jeric_synergy
11-14-2011, 09:58 AM
I have not tested this yet, but I see that Heading and Pitch also have "Align to Pole" options, just like Bank. Maybe Align to Pole is targeting under another name/algorithm.
lol, you know me well enough to guess what my next comment would be.

PS:
AFAICT (comp is busy rendering), since it seems that the "Point at Target" choice is always ghosted for Bank, perhaps the menu is just a case of code-sharing for consistency/laziness.

Celshader
11-14-2011, 10:15 AM
lol, you know me well enough to guess what my next comment would be.

PS:
AFAICT (comp is busy rendering), since it seems that the "Point at Target" choice is always ghosted for Bank, perhaps the menu is just a case of code-sharing for consistency/laziness.

I suspect "Point at Target" uses different code for its targeting than "Align to Pole" and cannot work with Bank.

I do not know what the advantages/disadvantages of using "Align to Pole" over "Point At Target" would be for Heading/Pitch. Perhaps they behave differently when used in combination with other motion modifiers like IK and Follower.

RebelHill
11-14-2011, 01:04 PM
The reason banks excluded is because it makes no sense.

point straight out ahead at something, a mug, the tv... the dog. As the thign moves, and you keep pointing to track, or target with it... you can still twist your arm anywhich way you like around its axis... basically... the point in space that you point towards can never have an effect on the twist as the twist, or bank axis, is always aligned to the target vector.

If you're wanting to "aim" the bank handle/axis toward a given item, use pole item, which is kinda like target for bank axis... but you can never have all 3 axes pointing at the same item, as all 3 axis can never align on top of one another.

jeric_synergy
11-14-2011, 02:58 PM
If you're wanting to "aim" the bank handle/axis toward a given item, use pole item, which is kinda like target for bank axis... but you can never have all 3 axes pointing at the same item, as all 3 axis can never align on top of one another.

Then "Point at Target" should be excluded from the Bank axis menu, not just ghosted.