Troubles With My 3D Model

I'm still having some troubles with this 3D model of the monumental entrance for this project. I was able to SWEEP the top cap of this structure in place. It's not perfect but it's close enough for government work.

The problem is now I need to fill in a large gap that is three dimensional and curved at the top on a radius in two planes. I guess you could call this a compound curve. It curves to the right as well as curving upwards at the same time.

Problem is the drawing is 1.9MB, 1.6MB compressed so I first need to ask for help in how to get it posted so others can perhaps assist.

can you delete other elements after saving a copy and only post the entrance?

I took out most of the other items and it's now only about 200K in size.

The trouble spot is the red polyline shape on the left side of this structure. I can't say that I've got the points plotted on it accurately but I did my best by building the 3Dpolyline snapped to the midpoints of the segments in the curved cap at the top.

The SWEEP command got the curved top cap in for me but as you can see over on the left something did not quite go right but that's not my problem for the moment.

This problem is similar to the genleman who posted the mine tunnel drawing yesterday. I played around with it and only got the same roller coaster effect that he was getting. Any advice would be appreciated.

Monumental-Entry(2).dwg

Okay, I still need to repair the problem with the top cap, but I approached it from another angle and started breaking it down into smaller parts which I can UNION later. I got it this far by using what is known (20 ft radius and 28.9684° segment that is 4'6" tall). I then did a SOLIDEDIT to increase the height and then sliced it to a known reference point.

The trick is still how to get the compound curve part of this defined so that AutoCAD can either slice or subtract this from what's not needed.

Monumental-Entry(3).dwg

is it possible for you to take a screen shot and circle where the issue is. I dont see any red lines indicating a problem. is my screen shot where your issue is? i see what you are talking about with your top cap twisting.

im sorry i just dont know exactly where the curve issue is you are referring to.

Thanks for your assistance on this. I have attached a partial screen shot of the problem. The yellow curved cap is in place and although it's not exactly as I want it, it's close enough for government work, as we say.

The magenta solid is what I need to adjust so that the yellow top cap runs continuous along the top. The magenta and the yellow solids are both curved on a 20 ft radius when viewed in plan. The trouble is that the yellow cap is also curving up at a 2 ft radius near the end when viewed from the front.

I'm finding that breaking it down into the pieces I know are there seems to be working. In the end, I'm going to have to lay this back out again and find a way to get all the points matching up. I mean if the guys in the field who don't even speak English can build a form to pour this thing, then I certainly have to find a way to lay it out in AutoCAD.

bill, are you drawing this just for visual representation or does the actual entrance way need to be spec to this drawing? If so where do you want to cut the pink block at?the bottom edge of the top rail?

I think just looking at it real quick that you can use the face of your top cap as a slicing surface tool. I havent tried it so i dont know if its a valid surface or not but im assuming that if you did a sweep for the top cap that it would be. Ill give it a shot when i get a chance.

okay so it didnt like that as a slicing face. I used Solidedit>face>copy and i created faces of each one of the section of that top rail that intersection the rectangle you are trying to get rid of. then i just extruded each one(shown in black) and subtracted them. I left the top corner so you could see it. I wouldnt say this is the best or only way to do it but i just didnt have the time to mess with it, sorry.

Thanks a million for your advice. I will have to digest the process a little before I understand it fully.

My model was thrown together so fast that I had inaccuracies in several places. The other thing I noticed is that the shape I SWEEPED along the curve did something similar to the gentleman's drawings with the mine tunnel, in that it seemed to tilt on it's axis as it made it's way along the curve. I am trying to layout the difficult compound curve that I'm having so much trouble with in a new, fresh drawing. This time I'm reasonably sure that I've got the arcs and the endpoints of each line and arc in the correct places. The only way I've found to join these segments into a 3DPOLY is to DIVIDE the arcs into a bunch of nodes and the manually draw the 3DPOLY along the way. Also I had to shorten Arc 'A' to the right and then add a line from line 'C' over to the new end of Arc 'A'. Otherwise I cannot get the 24" fillet in there. The trouble is I still end up with a small chunk of the shape sticking above Arc 'B' when I do the sweep and it looks like crap. I guess I could cover it up with another surface.

Can you take a look at this schematic? I've narrowed it down to just the physical properties of this top cap which has the wicked curve and fillet. Sorry to be so dense about this but if I can make this one stick, then I'm sure it will be worth the time I spent on it.

schematic(1).dwg

sure thing bill. ill take a look at it now and see what i see:)

Yes, this is what I suspected. When I do a VIEW (Left) on this after the SWEEP, I can see that the shape gets out of level. It should remain level and plumb to the horizontal, but it's obviously tilting. There is more to this SWEEP and EXTRUDE than meets the eye.

BTW - this is a monumental entrance for a local University here in South Florida. It's gonna look great once it's built.

well i took a look at things and i started playing around with it. Got a loft that worked and acad locked up on me with a fatal error:). I managed to get one screen shot.

So what i had done up to that point, first i changed everything you had yellow to blue just cause i couldnt see it on a white background:). I then drew a straight line at 90degrees to your vertical line(where the radius up needed to be), snapped that to your arc and then created an arc and moved your arc to that end point. You can also see i drew another line from your center point out to there.

Next i copied your profile over to all the points you see in the screen shot and rotated them accordingly. I created the top rail with a loft. Not because it was going to change shapes but this would allow me to use the cross section(profile) and a path to follow or guide curves. I did this in 3 sections.

So basically I used a start and end cross section (your T piece) and a path for the loft to follow. Im going to redraw it now so hopefully no more fatal errors happen

okay no fatal errors this time. Here are a few more screen shots along the way.

Now you will still have an issue here with the way the top cap meets at that hard 90. This is something you may have to ask yourself how will they build it. im going to fix it with a few extruded faces and a few slices which i will take some screen shots for you as well. I want to try something out before i post pics of the slice. If you have any questions on what i did in the screen shots below let me know

I've changed the name of this thing from concrete cap to Cobra Snake. Mainly because it looks like a cobra snake but also because it keeps biting me in the you know where.

There is obviously more than one way to do this. It's tedious at best and I just hope someone could come up with a single click method but I doubt it.

I will study your method in depth but at about the same time I did the following:

1. The 3DPOLYLINE was created by DIVIDING up the arcs into equal parts so I could trace them out with the 3DPOLY tool. The short arc 'B' was DIVIDED into 4 parts but I DIVIDED the big arc 'A' into 32 parts to try and achieve some smoothness. And just like you found, the only way to get the 24" vertical radius in there was to draw a regular line from the bottom of line 'C' to a convenient point at least 24" away along arc 'A' and then trim arc 'A' back to this point.

2. Once I saw the trouble at the top I found like you did that this was going to have to be more than one section in order to smooth out the transition at the 90° corner between line 'C' and arc 'B'. So I broke the 3DPOLYLINE at the 90° angle and thus ended up with two sections, unlike your method which used three sections.

2. This time EXTRUDE worked. First on the long curved portion and up the radiused fillet. Then I repositioned the shape at the left end of arc 'B' and aligned it with the XY plane. EXTRUDE got it out to the 90° corner.

3. The 90° corner did not come together at congruent points so I did some slicing and trimmed it up for appearance sakes only. When the concrete workers build the form I bet they run into the same thing. It's just that their model of 2x4's and plywood will be more forgiving to them than AutoCAD.

Once it was done, it looked like a big Cobra snake rearing it's head up to strike. Thus the new nickname for it. The men in the field will get a kick out of this. Now to just paste it back to the main drawing, which I can't do until I'm back in the office tomorrow. Then I'm going to render it and when the product is finished I'll post it here.

I still believe there has got to be a more efficient method than this. But this is close enough for government work...right?

well the issue is(as far as i know) that you wont be able to do this in one swoop so to speak because of that hard edge. Really if you want to get this thing nice and smooth there are other ways to do it like using a surface to slice a solid or using the boolean operation INTERSECT with some creative modeling but these will be more involved than what you are doing now. I havent found any easy way in autocad to make the top part and the main "snake" to line up nicely. No matter how i tried to slice this thing i was getting issues. there are ways to get around it but nothing quick and simple(that i know how to do).

i should also mention this is very easy in solidworks or inventor:)

here is a trimming option for you. Make a copy of your section if you did it in multiple parts like i did. explode that once and it will reduce it to faces. you can thicken these faces creating solids and use them for subtraction. Ill explain a bit more with screen shots in a few

here are some pics for you. you can see in the last pics that the side of piece is smooth after the subtraction. You would have to pick/choose what/where to subtract and what needs to remain for construction purposes.

Thanks again dude. Your advice proved invaluable on this. Turned out that I had the drawing file I thought was at my office here on my network. So I made a few runs with the render in ACAD 2K9. Still need to fill in the gaps at the column and the curved wall just below the snake's head, but that will come tomorrow. And I gotta work with the lighting on this. But the overall certainly looks like a realistic rendering of the almost finished product. They can't decide on a color or if they or going to veneer it with brick.

Here's to swimmin' with bow-legged women !

very cool bill! should be a very interesting form for that:)