Vertex/Vertices Creeping

Support Modeling
1

First post here, Hello !

Ive struggled with this for 2 nights now, only for it to strike me again. So help required :slight_smile:

Im making a modular building. My first time, so not got alot of knowledge, but its been going alright.
Been sticking to the powers of 2 . With main sections being 512 by 256 high. Everything has been built with Snap to Grid enabled also.

I never noticed till i was modeling a roof section, with fairly simple straight edges. When i look at the vertices on the outside edge they have creeped from, for example, 512 to 512.000034 or 512 to 511.000065
Not every vertice moves, but most seem to.

Its not alot, but it gives me some tiny gaps between each section of the building (diffrent objects) when i try to snap them together, and dont align properly.

I thought i had done something wrong, so i spent most of last night trying to work it out. But everything was built with snapto enabled so i dont see it possible that ive moved them myself, as its offgrid sizes.

So tonight i just deleted the roof section and remade it. Everything was going fine till near the end, perfectly aligned, then next thing i know the verts were creeping again. Again, cant see anything thats caused it.

Ive checked some of my other pieces also, and the verts have creeped from their exact 512, 256, 128 etc sizes.

Ive tryed setting the sizes back to the exact ones in the type-in box, but then it seems the pieces are offgrid anyway and still dont line up.

I would just make some covering pieces etc, as i have done that to cover some texture seams anyway, but its for in a game so id rather try and get it worked out.

Just noticed this was getting rather lengthy… Any ideas/help would be much appreciated :slight_smile:

Edit- To the mod who moved this…Sorry, somehow i managed to miss all the diffrent support forums,just went straight for technical

2

it sounds like a bug. I would recommend making a bug report, so hopefully it gets fixed by the next release.

3

Found this old post, from 2004. Sounds like the same problem to me.

http://blenderartists.org/forum/archive/index.php/t-19091.html

"After scaling it down, I noticed that sometimes I’d loose symmetry in places I made a conscious effort to maintain it. This didn’t happen prior to scaling it down and I believe it might be caused by what appears to me to be fixed point numbers used to store vertices and rounding errors that cause a slow creep on a few vertices.

When I’ve seen it, its generally been after some major editing and if blender is storing vertices in fixed point to the 3 decimal places it appears given what I can see when I mash NKEY, its entirely reasonable I’m just seeing errors caused by running into precision limitations. It might also just be something as simple as rounding -1.5 to -1.0 instead of -2.0. I’ve made that mistake before in my code, :wink: ."

Ive looked up Blender rounding Decimals on google, and found quite a few pages, but it doesnt really seem to be a bug from what im reading. Just the way blender rounds down odd numbers etc.

So, will try and get some of the meshes into a game editor and see how they perform/look.
I can only see the gap/misalignment when i zoom in close as possible in blender, so maybe it wont be too noticable ingame.

I’ll learn all this some day :stuck_out_tongue:

4

(edit) my last post was a bit redundant so I edited it out, hope it works out.

5

if you work with normal scale
you are limited to 7 digits and 3 digits after the dot like 1234.789
unless you change the scale but then you still have only 3 digits after the dot !
and this is to make blender respond faster !

only way would be to ask someone to make an SVN working with full 15 digits python precision
which might possible if someone is ready to do it !
but this would certainly make blender more precise but also more sluggish!

but have not seen one done yet

so there is a limitatons on the precision which blender works with

hope it helps

6

RickyBlender is right about the approximate number of decimal digits of precision (about 7) that you can expect to get in blender measurements. This is because inside Blender all vertices and most calculations are doing with what is known as “IEEE single precision floating point” numbers (you can Google that). It would be quite difficult to make a version of Blender that used double precision instead - a large amount of the source code would have to be modified or maybe there’s a hacked compiler chain that could do it. Anyway, this should not have to be the solution to your problem.

You would probably be better off making the maximum size of your building units something in the 10s rather than in the 100s.

I wonder if using Snap to Grid was a problem here? Maybe you should snap to existing vertices if you want them to line up?