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dzcube 16-12-2009 11:16 AM

easy modeling issue causing trouble
 
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hello everyone.....

trying to accomplish a simple task thats causing me a bit of hangups.

so what i want is a shape created from a cylinder. the first pictures gives you an idea of what the shape is (curve projected in RHINO).

now, i want to make this shape in polys. (the final shape should have a thickness, just like a tube).

but i went ahead and tried a couple of different strategies with nurbs intending to convert to polys since that seemed the most straightforward.

1. i have the precise curve i want, so i tried projecting it in maya, and it gave me all sorts of issues like not being able to trim. i think this was because i was projecting a curve that would surround the surface completely by ensuring my curve was = to the diameter of cylinder and this was causing trouble the curve on surface or something...

after trying some other workarounds, i concluded that nurbs in this case was probably not worth it.... unless anyone knows what im doing wrong. again, such an easy task causing issues.

so on to polys..


2. the only way i can think to create this in polys is to create a cylinder with many vertical segments, and drag the CV's to align with the reference curve in a side view.

is this the only / best way to do it in polys?

and if so, is it correct for me to say that working with poly's will most of the time involve aligning things to a reference curve / image instead of having the precision of nurbs and things like projecting exact curve on the surface......

hope to get clear on this,

thanks!

daverave 16-12-2009 01:35 PM

Hi dzcube
I was not sure what I could do so I tryed project curve on surface tool this worked ( on a nurb cylinder), you need to do this from a side or top view not perspective...............dave

PS. sorry just leave a curve on the cylinder what use is that?

dzcube 16-12-2009 04:56 PM

thanks,

i was projecting from a side view. i'm projecting so that i can trim....

thats where i'm getting the problems.... it won't trim for some reason

ctbram 16-12-2009 05:15 PM

This is really not an "easy modeling issue".

Doing it all in nurbs within maya works; however, nurbs tools in maya are finicky. You can achieve a nice result though.

Converting it to polygons is trickery and has a lot of steps - each of which can cause problems if not done correctly. But in the end you can get a poly surface which you cannot get in Rhno since it's an all nurbs based modeling package.


Here is an outline of the process and some renders...Is this what you are trying to achieve?

http://i181.photobucket.com/albums/x...th_process.jpg
http://i181.photobucket.com/albums/x...reeQuarter.jpg http://i181.photobucket.com/albums/x...reeQuarter.jpg

Let me know if this all makes sense. If you are really confused I can try to make a camtasia video of the process for you.

Here is a similar thread on using booleans and surfaces to create a womans shoe...

http://srv01.simply3dworld.com/showt...threadid=33381

dzcube 16-12-2009 05:53 PM

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interesting indeed...

i didn't consider booleans because i've run into a heck of a lot of issues with them.

i never know when is an appropriate time or not. in general, i've heard best to stay away from them.

but yeah, i guess there are a lot of steps requiring a careful eye.

so after these suggestions i realized that my starting point will have to be a little bit different. attached are some images of the physical model.

i won't be able to start with a pipe since the top surface will be enclosed......

any ideas?

ctbram 16-12-2009 06:27 PM

ah thanks for the actual physical model.

I will toss together something for you and upload the .obj.

Starting with a pipe will still work. I will just close off the top afterwards

ctbram 16-12-2009 07:25 PM

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Here is a modified version that is very close to what you need.

http://i181.photobucket.com/albums/x...r/th_v2_01.jpg http://i181.photobucket.com/albums/x...r/th_v2_02.jpg
http://i181.photobucket.com/albums/x...r/th_v2_03.jpg http://i181.photobucket.com/albums/x...r/th_v2_04.jpg

and here is the .obj file so you have a starting point. It contains the final object and all the master objects used to slice it up so you can make changes as needed. Best of luck.

Let me know if you have trouble figuring any of it out.

ctbram 16-12-2009 07:52 PM

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Well actually this is closer (lol).

http://i181.photobucket.com/albums/x...r/th_v2_05.jpg http://i181.photobucket.com/albums/x...r/th_v2_06.jpg

and just out of curiosity, what is the physical object you are modeling? I mean that tube, is it part of a larger overall object?

dzcube 16-12-2009 08:29 PM

thanks man! really appreciate it.

it's a design for a plastic bottle in which a cartridge is to be dropped into the bottle, and filled with water (the opening has not be designed yet).... which is why there is a vertical spout at the top....

also, any comments about what i said about bool operations and how many say they should be avoided if possible?

ctbram 16-12-2009 09:39 PM

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As for booleans. I use them all the time. I have commented several times in this forum that booleans are very useful and powerful tools. They get a undeserved bad rap because folks just don't know how to use them properly.

Just in case you need it. I booleaned the other part of the cylinder.

http://i181.photobucket.com/albums/x...r/th_v2_07.jpg http://i181.photobucket.com/albums/x...r/th_v2_08.jpg
http://i181.photobucket.com/albums/x...r/th_v2_09.jpg http://i181.photobucket.com/albums/x...r/th_v2_10.jpg

and here is the obj.

ctbram 16-12-2009 09:50 PM

Here are some smoothed wire frame images...

http://i181.photobucket.com/albums/x...r/th_v2_11.jpg http://i181.photobucket.com/albums/x...r/th_v2_12.jpg
http://i181.photobucket.com/albums/x...r/th_v2_13.jpg http://i181.photobucket.com/albums/x...r/th_v2_14.jpg

dzcube 16-12-2009 10:00 PM

yeah, i guess thats the key. knowing how to use them properly.

a few follow questions:

1. in your original instructions on booleans, you say

"8. delete top and bottom caps, delete floating verts"

do you mean by deleting all the individual faces of the cap? if so, how do i easily delete all the vertices that were left behind?

2. and then in #9, you say to cut in half. cut what in half, and why?

3. for number 12, insert extra loops through the "insert edge loop" tool?

4. and as for .obj objects. im having some issues importing them in.
thanks!https://dl.dropbox.com/u/1515390/Scr...03.31%20PM.png

ctbram 16-12-2009 11:08 PM

lets start with q4. The message you are getting is my fault I saved the obj file with groups selected. But don't panic all the objects are going to come in and be COMBINED so when you select it will appear as though they are one object.

To separate everything into individual objects pick the object and everything will turn green, from the polygon menu select Mesh>Separate and you should get a group containing all the individual objects.

You will also have a bunch of extra xxxsets in the outliner. You can just select all the xxxsets and delete them all but two will delete.

For questions 1 to 3 I think it will be easier for me to put together a camtasia video for you. This will not take me long and will be easier then trying to type up the answers. I really did not put a lot of detail in the process description so I am not surprised you are a bit confused. Not to worry. Check back here shortly...

ctbram 17-12-2009 03:33 PM

Sorry for the delay in getting this uploaded I got side tracked last night.

Here are two videos showing how to use profile curves to make cutting planes to use to cut up a polygon pipe using booleans.

The first video is about 15 minutes and covers the creation of the top section and the second video is only 5 minutes and shows how to create the bottom section for a perfectly fitted completed part.

I dropped the step to split the model in half as it was not necessary.

I hope you find this helpful. Please feel free to ask any questions if anything confuses you.

I am not sure how much bandwidth I have remaining on screencast.com so if I run out and you cannot run the video I will put another copy of both on YouTube.com later today.

Here is what we make:

http://i181.photobucket.com/albums/x...inderTitle.jpg

Here is the link to part 1 - the top section...

http://www.screencast.com/t/YWVjODU5ZDk

Here is the link to part 2 - the bottom section...

http://www.screencast.com/t/NzIxODEyY2

Enjoy! I will post the .obj final file later.

dzcube 17-12-2009 07:24 PM

you are the man. :bow:

you rebuild your curves. i hadn't thought of that.

is there any major difference to setting your loft tessellation controls to x number of U's which gives the resulting loft several points as well?

rebuilding the curve seems cleaner and better workflow though.
------

also, when i try to bridge, i get this twisted you see there. however, if i first bride one edge, and then follow with the rest of the surface edge it works.... any idea why?


thanks!

http://dl.dropbox.com/u/1515390/Scre...38.15%20PM.png


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