Hello All,
I've been working on a physics based track. The track has lots of 'glued groups' that are using OPE to rotate on multiple axis.
After editing the group by means of adding new objects to the group, my pivot point moves or the axis of the pivot point changes making all the OPE movements completely out. Needless to say, this is hard and very annoying to work with.
So, after a lot of effing around, I've come to a rather elegant solution.
1: Preventing pivot point from moving after adding/removing items from glue group:
When you glue objects together, the pivot point can be set to use 'Centre of Mass'. With this in mind, I placed a simple small item (a scaffold mount) and gave it a mass of something stupid like 10ton. I then made every other item of the glue group 0.1kg. Therefore, using the 'Centre of Mass' as pivot point ALWAYS is the centre of the scaffold part.
The only downside of this is that it throws out the mass of your glued object and if you intend on using physics it could act a bit odd. Maybe if you make the heavy item Max weight, you could leave all the other items as normal weight then just make the heavy item invisible and decoration only - Not sure; I have not played with this aspect.
2: Fixing pivot point rotation after adding/removing items v1:
When you add an item to a glue group, ALWAYS add the item AFTER setting it to it's default position in the game (i.e. Click RS 2 times). Then simply sub-select the item and move as necessary. Modifying an item in a glue group does not effect the pivot point. I.e., Spawn object, Click RS twice, make mass 0.1kg, unselect object. Select glue group, shift-select new object, glue group. Unselect group, shift-select new object in group then move/rotate/etc as needed.
3: Fixing pivot point rotation after adding/removing items v2:
After you build a glue group, Highlight the glue group, then Unglue all items then Reglue all items. This resets the pivot points XYZ axis the align with the XYZ of the drive line (i think it's the drive line). If you have used the 'Centre of Mass' thing above, This is an extremely quick and simple way of making the pivot point reset in a way you can plan for.
I hope this helps people. I know that for me, this has sped up using OPE with Glue groups massively.
You could just select your glue group, go to select pivot, click RS twice, then move the pivot back to where it was. That way you dont have to unglue anything.
I probably should have given a bit more info...
I accept that in a lot of situations where you are making a single use only glue group none of this will be important because you only have to do it once. This only really comes into play when you are stuffing around with different instances of the same glue group over and over.
However in the level i'm making, it is kind of like a Portal level. The whole track consists of panels that are raised, tilted, rotated, pushed or pulled on a 'swivel hinge' that i've made using a ball and socket out of small parts. I've made several different panels that do different movements and saved them to favorites. For the level, it is important to have every glued group to rotate on exactly the same point otherwise when the OPE animation is finished, panels dont line up right and the rider ends up either dropping a smidge or hitting a small lip - small as it is, it does affect the overall flow of the level. The last thing you want is to be fanging along a visually flat set of panels and hit lip after lip.
Because the entire level is made using these 7 or 8 base Glue Groups and then having more items added to them, it makes the whole process a lot quicker if the pivot point can be easily assigned a position and orientation.
Also, Unless i'm doing something wrong, I cant rotate the pivot point at all once the glue group is set. If I select it, clicking RS only sets it to the drive line - it dosent seem to rotate it.
I've has no problems rotating hinges at all. Not sure if it's different for other physics joints. I've been using 90 degree hinges, and the little pie wedge is fairly easy to see and orient.Also, Unless i'm doing something wrong, I cant rotate the pivot point at all once the glue group is set. If I select it, clicking RS only sets it to the drive line - it dosent seem to rotate it.
Not hinges mate. Talking about pivot points in relation to OPEs. Yeah, hinges arent a problem.
