Extruding polygons not uniform?

[ob1]

Hello,

I have a problem when extruding edges, I want to extrude a detailed ledge that goes all the way around a building (Cube). When I extrude the polygons I am not getting a uniformed extrusion instead I am getting a result where the corners do not extrude as far out as the sides. I then have to go in and move the corner points to fit in with the normal side extrusions. I hope this makes sense. Am I doing something wrong or is it a Maya thing. I work with buildings all day so this take's up valuable time. Any tips or scripts would be appriciated.

Thanks.

[joojaa]

It has to do with a mathematical truuth that many people dont seem to realize. Its one of those things where, tools do exactly what they do.

Se if you extrude a edge your actualy making a new face and then manipulatin the end vertices to move a certain distance in the normal direction, Now if you have a90 degree corner that normal is 45 degrees. And offcourse because you are making a ledge youd want the length in 0degrees to be the same all over the place but the vector is actualy 45 degrees turned, wich means the distance of 1 is in 0 degree direction sin 45 or 0.7071... instead of 1.

So i do suggest you extrude with edges not connected in wich case they exryde in the right direction and then add a face in the corners.

[ob1]

Now that I think about it, it's the same in 3dsmax, so I guess it's just a fundamental problem.

Cheers JooJaa.

[joojaa]

Yes well the problem is that the computer cant know wich direction is the one you want to measure along, As its only easy to measure along the move vector, wich now is skewed. This does not man such a tool cant be made, its just that ist hard to do one that can asume the direction you want.

[failure]

You do know that clicking on the small circle in extrude mainpulator switches between local and global space. So if you need to extrude everything "up" just switch to global and drag manipulator y axis.

[joojaa]

okay this depicts what he gets under A) wich is length along the average direction of the surface normals.

Whilke he wants wich ia sum of the normals (in this special case only tough).

[failure]

It's pretty wise to use nurbs for things like this.

[mikedin]

FYI,

MAX extrusions do in fact work much better. I've extruded a million types of profiles along paths, highways, cornices etc. MAX at version 2 I believe also had an option to compensate for what Jooja is trying to explain which simply scales your profile up at corners where bends exist. for example the second corner in diagram "B"; the shape would need to be scaled along the shapes local x or z axis %150.

Alias really should fix this. Another caviate is Nurbs parameterization. MAX has better controls for tiling a texture map along the extrusion. There is no distortion.

Just my 2 cents as I see this debated constantly.

[failure]

In reply to:MAX extrusions do in fact work much better.

Not true. They work exactly the same.

[mikedin]

Umm no they dont.

[failure]

Both "misbehave" in a same fashion. Just use different averaging algorithm.

[joojaa]

Yes both misbehave equaly bad. But to say its not uniform is a lie, the extude original poster was after is NOT uniform the maya extrude is ona more general term uniform.

And no max does not compensate for corners (you can easily test this make a stairstep and add points midstep and extrude if it becomes wonky it does not compensate)! Atleast not wehn i last chekked 3 weeks ago. I think the difference with maya and max is that max uses the face noemals while maya uses the vertex normals. So makieng normals face would make maya behave exactly like max.

Note taht act of compensation is right if one asumes the face is the actual geo, but we all know taht POINTS are so it isnt.

But anyway making a function to do this isnt hard. Again im not interestrted in doing one. I dont need it.

I investigated this a bit and max indeed does do this slightly samrter for thsi special case, BUT still not like the original psoter wants.

[mikedin]

It's the checkbox "Constant Cross-Section" under loft parameters that were speaking to here directly. This is on by default in MAX and sovles the problem you speak of. There is no option in Maya for this. One of the things I love about Maya is the options for most of it's tools. Unforunately lofting whether you use them or not is a hall mark of 3D modeling and should be very robust. MAX lofts don't Misbehave in any way (Give me an example). If there is pinching at a vertice or turn along a path, MAX won't trim that surface there but I don't know of any package that will. Dbl check this and you'll see what I'm talking about.

Also Maya has a know bug in it's extrusion where it will flatten a profile at time where a turn exists. Jooja you know about this as I remember the thread a while back and another HE3D guy created a Maya file demonstrating it

[joojaa]

Your talking of different tool!

Extrude and poly extrude are 2 different things (they work in different direction extrude and maxs loft works by dragging along and poly edge extrude and face extrude works by pushing outward)!, and yes extrude has a problem. BUT this has nothing to do with the maxs loft function. Or this particuler problem either. Its not the same syptom.

Its differet tool, but yeah you could do this in the same fashion. Same problem persists tough. And yes thatway max can circumvent the problem if done thisway, your right. IN fact thinking thisway its rather easy to device a tool for this.

Must look into it. Thankyou for kicking be in the back to se the other way around, i offcorse used this to kick someones but 1 month ago but..

Also the extrude bug only happens if the last point is at the croner. And its closed so using polygonal geo like max uses 99% of the time would meakke it easy to avoid entirely unless ones realy stupid. (or does not know off the bug, wich amkes it stupid only untill youve done it once)

[joojaa]

Heuraka!

Okay heres what you do! You take and download the alias bonyus tools pack. Bacause the edges to curves script comes handy here (hey i dont hanve the obonus pack but i know it does come handy here).

Select the edges, offset the edge (the offset cvalue amight be negative experiment). Then poly loft the two curves together. and viola it works just like supposed. As long as you didnt have wonky corners (also it does ofset in the apparent normal direction not the face normal but for buildings it works fine evenm if you are skewed).

QUESTIONS?

[failure]

You cheated !
That was nurbs modeling !

[joojaa]

no i didnt Theres no such thing distinction, while theres poly modelling all NURBS tools work equaly as poly ones.