Trouble with a Lattice

Hello

I am trying to use a lattice to deform the bottom of a tyre. I succeed with a simple torus in getting the approach to work, however, when I tried this on my real tyre this happened, repeatedly:



I have no unapplied rotation or scale, so I remain confused. This is my first foray with a lattice so I don’t have much experience to fall back on. Can anyone suggest what might have gone wrong?

Thanks, Clock.

Yes, the road is indeed paved with miss-intentions, to paraphrase the old ditty.

I have read your link - well most of it and here is a workable solution for me.

  1. Create a lattice of radius 1 - NO more NO less.

  2. Scale it to fit the tyre.

  3. Add Lattice Modifier to the tyre and select the lattice.

  4. Play with lattice happily, all is well, tyre deforms nicely and keeps the ground contact deformation on the ground even when I rotate the tyre (I am one happy teddy).

Alternative not-quite-so-good method:

  1. Create lattice of suitable radius to fit the tyre.

  2. Add Lattice Modifier to tyre and select new lattice.

  3. Go and bang my head on the wall until stupor pervades, throw neighbours cat at the wall, etc. - this is more rewarding than trying to play with the lattice/tyre. :mad:

I spy with my little eye something beginning with “B”. I have no scene scale applied - not even set any units, just a new file to which I appended a tyre from my Tractor Transmission project (in the WIP section)

But at least I have a workaround - thank you so much, Clock.

No, this isn’t a bug, this is a common early misunderstanding about how lattices work. Do not apply object scaling and rotation on a lattice. That’s usually counter the advice you get for every other type of object, especially when it comes to rigging and animation, but there’s a reason for it that is only obvious when you understand how lattices work.

The lattice deforms your mesh based on the difference between its vertices’ local position and those of your mesh. When you apply the scaling and rotation on any object, it makes those transformations “real” in edit mode. This basically means that even if you scale and squish your lattice in object mode so it fits your mesh, it is considered un-deformed in edit mode. Unless you apply those transformations to the object. Now your lattice is pre-deformed, so your mesh has no choice but to jump to fit it.

So just delete that lattice and make a new one. Scale it in object mode and keep your fingers off ctrl-A this time. You can and usually should apply scaling on every object except lattices.

The documentation for lattices actually makes note of this but it doesn’t quite explain the whys and wherefores. http://wiki.blender.org/index.php/Doc:2.6/Manual/Modifiers/Deform/Lattice

This has nothing to do with applying the scale…

Scaling in Edit mode is a no-go for a lattice, I get that. Then why suddenly (starting with 2.72) expose the new “Radius” setting to the user when creating the lattice, which seems to be equivalent to an Edit mode scaling? That’s the “bug” - call it “nasty usability glitch” if you like that term better.

Why expose settings to the user that seem to serve no other purpose than to spoil the lattice’s correct function? This is an accident waiting to happen and frankly I fail to see how this could be anywhere near “intended behaviour”…

Thank you sir, this is what I did in effect, but every time I create a lattice of anything other than radius 1, it messes my tyre. So I created a radius 1 lattice, scaled it in object mode (I have removed my CTRL and A keys, so I can’t repeat my erroneous ways) and it works fine. What I don’t understand is why give me the option to mess up by letting me loose on the lattice radius figure?

Thanks for clarifying things for me. Clock.

PS by “unapplied scales, rotations…” I was referring to the tyre, I did not apply anything on the lattice, although this was pure ignorance on my behalf - I just didn’t do it and don’t know why!

There’s no reason to use that radius option. I don’t know what it’s there for. Just scale the lattice to fit your object and leave the radius alone. The radius option could serve a purpose if you wanted to use a lattice as part of a rig that enlarges a rigged mesh while leaving you able to use smaller controls, but effectively when you use a radius larger or smaller than 1, you are creating a pre-deformed lattice. It can be a useful feature, but if you don’t want to use that feature don’t use it. A radius of 1 with object mode scaling is the default. Just because there is a value available does not mean you need to change it.

I didn’t apply the scale to the lattice - I applied it to the tyre.

So it’s SOLVED thank you both. Use radius 1 lattice and scale it in object mode to fit, don’t apply scale - works every time.

Here’s the end result:


Thanks again, Clock.

Fixed in 2.73: https://developer.blender.org/rBba76f0c6a29e3955ead99b32d2fb41c534c1dbc5

In 2.72 the add-object radius setting was exposed in all object creation panels. It used to only appear for mesh and curve objects I think. There radius = edit mode scaling makes sense. Some objects use a different label but it works the same (icosphere says “size” not radius). Add-object radius for lamps is exposed now too but useless for some types of lamps (it adjusts the distance falloff setting).

That other report / debate linked above is about scene scale affecting the lattice tool. I haven’t looked into that one.

Sorry Clock. A bit off-topic I know. Nice tire. That’s a nice tractor you are building. I like tractors.

-LP

No problemo Larry - any background info like this is useful to me. Thanks for the comments on the tractor - I too like them, all I wanted as a child was a toy tractor - never got one, resulting in deep psychological scare, so when I was in my thirties I bought a real one! Now that I have sold it, I decided to make a model. The model is not authentic and will never have all the castings, body etc. Maybe some day I will get the drawings and model the real thing. The model is all about gears, engines and mechanical rigging as a learning exercise for me. Now I am really hooked on it so it’s also a learning exercise for materials and modelling as well.

Cheers, clock.