topic Re: Problem with the height of the land in Modeling

Problem with the height of the land

Anonymous — Mon, 14 Jul 2008 16:20:41 GMT

I have some troubles to drop the land's height, i put in the details of my land, around 173000 in height,
Wat i did is, i go to 'view'--> 'element 3d view'--> 3d cutting place' draw a line trough the land, then activate '3d cut way'. I can see the height of my land is dropped in 'Generic perspective' but not in the 'elevations'. what steps am i missing?

PS: i heard that i have to go 'design'-->'story settings' to change some settings, if so, what kind of settings i have to change there?
Anyone can give me a help?

Re: Problem with the height of the land

Anonymous — Tue, 15 Jul 2008 17:15:59 GMT

You don't really need your land model to extend all the way to sea level do you? Why not just model the part near the surface? I find anywhere from 3-10m below the lowest point is generally enough.

The 3D cutting planes only affect the 3D window and views derived from that. Section/elevations are separate and each have a setting for top and bottom of the section cut.

Story settings, though related, have little to do with this.

Re: Problem with the height of the land

Anonymous — Tue, 15 Jul 2008 21:37:24 GMT

I do this all the time. It is alot easier to model the mesh when the elevation figures you enter are the actual levels, no need for doing maths in my head..
The way I get around this problem is follows:

1. Build the mesh as you have done using actual levels.
2. Now trace the mesh with a 100mm thick slab that is positioned about a metre below the lowest point on the mesh. Make the slab the same material and section fill as the mesh you are using.
3. Use Solid Element Operations to subtract with downwards extrusion using the slab as an operator and the mesh as the target.

This method will cut off the bottom of the mesh just like the 3D cutting plane, but will show correctly in both 3D and sections.

Re: Problem with the height of the land

Anonymous — Tue, 15 Jul 2008 21:56:34 GMT

I just set a sea level reference and model and edit the mesh relative to that rather than the mesh reference plane. There's no advantage as far as I can see to justify fussing with the sections/3D cutting planes nor the SEOs.

Re: Problem with the height of the land

Anonymous — Tue, 15 Jul 2008 23:31:26 GMT

Matthew is quite right you can simply insert a negative number in the dialog box (see picture) this will chop off some of the bottom.

If the land mesh is placed on the same storey as your floor slab you should position it's height releative so to place the SL=0 of the mesh at 0.

In your case if your storey is set to match a floor slab at 173m. The mesh should be placed at -173000 and you could put -150000 in the box I mentioned. This would place the mesh in the correct relative position with the bottom 150m missing.

Re: Problem with the height of the land

Anonymous — Sat, 19 Jul 2008 16:13:51 GMT

Thanks for help guys!

Re: Problem with the height of the land

Anonymous — Sat, 19 Jul 2008 16:30:03 GMT

Brewer wrote:
Matthew is quite right you can simply insert a negative number in the dialog box (see picture) this will chop off some of the bottom.

If the land mesh is placed on the same storey as your floor slab you should position it's height releative so to place the SL=0 of the mesh at 0.

In your case if your storey is set to match a floor slab at 173m. The mesh should be placed at -173000 and you could put -150000 in the box I mentioned. This would place the mesh in the correct relative position with the bottom 150m missing.

This is a neat trick also but not quite what I meant. If you set one of the two reference levels to sea level (relative to project zero - see attached) then you can simply adjust the mesh elevations relative to that reference level.

This saves having to do the somewhat counterintuitive negative thickness and eliminates the need for a sea level story height. In fact it separates the whole issue from story settings altogether.

Re: Problem with the height of the land

Anonymous — Sat, 19 Jul 2008 16:47:08 GMT

Here is the mesh settings dialog showing the height to sea level option.

Re: Problem with the height of the land

Anonymous — Sat, 19 Jul 2008 16:49:33 GMT

...and here is the dialog for setting the contour height relative to sea level. No story settings involved.

Re: Problem with the height of the land

David Shorter — Sun, 20 Jul 2008 09:31:37 GMT

Here is my 2 cents
I do not understand reference levels as (it seems to me) to increase the likelihood of error
It frustrates me that the info box and some of the other dialogues do not show the same values.
I have never really understand why you wouldn't work to real levels
It makes things very simple

Re: Problem with the height of the land

Anonymous — Thu, 28 Aug 2008 06:54:29 GMT

Well I recently stumbled upon this issue when modeling a large part of a small city for a civic remodeling project- it's a good kilometer above sea level roughly.
When I opened up the 3d window, after all the SEO's for the civic buildings and streets and walks (I modeled a mesh and extruded all the streets and sidewalk planes with SEO'd duplucate meshes- so I had 3 layered but at slightly different levels; say 20 & 40cm higher/lower)...I discovered that the BOG DOWN in 3d loading and movement was quite significant.

Using either of the above processes changed that and made the model "render" in the 3d window and openGL normally. Without using some method to reduce the visible land height, the computers were slowed to a complete crawl, and 3d movement was almost down to 2-5 frames a second at BEST -!!!!!

I.E.
Having the land RENDERED in real time with all the textures (perhaps if one wasn't using textures on the vertical planes?) simply choked up my Nvidia 8800gt video card and Dual core 2.4ghz cpu. And that is a fast video card and quite capable CPU!

So work arounds, and not rendering all the vertical planes TO sea level, regardless of the technique, seems to be something that is needed -esp. if you're going to check 3d or Z-plane dimensions!

I found that an SEO slab just below the bottom of my lowed point in the meshes was the simplest method- BUT BUT BUT- it interfered with SEO operations (there was a lot of them) with the rest of the model, and frequently I found myself needing to go back and forth to maintain that -bottom cut-off SEO. Which was a drag and took more time....

So I recommend the sea-level trick. I do this one now- and probably will do this method until GS releases or changes something about how this is done. I also recommend it for people who are on non-super new computers. It works flawlessly on my older rigs and portables and old video cards- no issues and extra CPU cycles to keep those extra SEO calculations relevant for the model!