I think the problem is that a true ellipse has a larger circumference than an approximated ellipse. Since an ellipse in cg is using a discrete method, contrary to a continuous method (like in paragraph 88), it will always be an approximation, hence it will have a smaller circumference. (see image below for an exaggerated example)
The result of this is that the last radius (or even several radiuses) will be beyond the trajectory you wish to draw. You can of course choose smaller intervals between the radius-lines, but you will always have some error in it. The question is: what error is acceptable for you and what can your computer handle? You’ll need to calculate the curve for only 0.5pi radians, but at 1e-4 radians (what you’re currently doing) this means over 15k calculations. Fortunately this scales linearly.
As a final question, how are you calculating the total circumference? Are you using Ramanujan’s approximation?
not certain about the name its a short cut version
which is something like [FONT=Arial][SIZE=4]
[LEFT]= (A/2) [93+ 0.5 3^.5]^0.5
A being the 1/2 the major axis
may be you have the right name
the main problem is not the precision of the XY values it’s more the angle at wich to get theses values which is the problem i’m having
in the senses that i need to get constant arc lenght at certain location or angle - Ex the columns for the roman colesseum
there are no columns on the main axis so there is an offsets
where you begin to set the columns !
sorry don’t know what happened to the size of the font here!
and i need to loop a lot to get high precision becaue i begin with an angle then calculate the XY then evaluate the arc lenght until i get >= to the arc lenght
so the idea is taht the smaller the increment is the higher precision is - it’s a convergent function at least i hope it is
and seems to be up to now
but i’’ be looking at parametric equations this weekend to see
if there is not another way to do it faster and with high precision
Salutations
[/LEFT]
[/SIZE][/FONT]
i will also check if this is not an a trancendantal equations and see if there a way to calculate the inverse
which i should have done at the beginning - but my math i a little rusted and slugish- sorry
while editing this post i see that it’s a hec of a mess sorry for that
I’m very interested in your project as I’m trying to model a 12’th century village church. (exists in real life)
The dome is causing some problems as it is hard to get the right concave shape.
Will your project be able to solve this type of arch/dome? I have tried to use the script vault 0.0.7, which works fine, except the arches are different in size, and I need them to be the same size. (and different shape as well)
I’ve attached a screenshot of my model to give an idea of what I’m working with.
The ceiling is rounded in the Y-direction, but needs to be rounded in the x-direction as well and in fact exceeding the center of the crossed arches a tiny bit.
i’v you ried playing with the Scale in x or Y Z to change the shape ?
normally theses arch vault are symetrical - Nomrally
questoion of stuctural integrity or they are overdesign and heavier thatn necessary
which cost more in term of manpower and material
I’ve tried to work with the models you gave me, but I can not get the right shape out of it.
I need to have the ceiling curve in both directions, as in a sphere, and it needs to connect to the cross-arches. The closest I got, was creating a curved guide-line from the cross-arch top-center to the center of the support arch. Then I extruded, rotated and scaled the verts from the supportarch, and made it follow the guide-line. Only problem was that I could not make it connect to the cross-arches in the right way. It’s a lot of extruding and scaling, but if that ends up being the only way, then thats it. Just thought a script could do this somehow.
The attached image is the closest I can get to what I need. There are 2 main differences to the image and my model:
There is only one window( in each pointed opening) in my model. (not important), but the opening hight is the same for all 4 openings regardless of the shape.
The shape of the opening (with no window) is not pointed, but it is a semicircle.
So if you look at my meshobject posted earlier disregarding the mesh in between the crossarches, you’ll see that this is the basic structure of the vault:
I have 2 arches crossed (they are semicircular)
I have 4 openings (2 pointed ones and 2 semicircular ones), the openings are the exact same hight.
The pointed openings contains the windows
The semicircular openings arches over the church-room itself. (obviously, as there wouldn’t be much of a church otherwise)
are you building a church model with rib vault arches?
i look at the pic and i’m not certain but i can see ogive type arches not circular one ?
are you certain theses are circular arches ?
do you have the site for this pic i’d like to check it out for myself
as i remember theses are rib vault arches and not circular as i remember
in classical architectures but may be i’m wrong
now the window are another part added to the basic arches
so i doubt if you will find any script that contains all theses details
this is too specific and general
i mean Crouch is building a script to do general arches of different types
and he told me yesterady that he should continue on it soon to add more type of arches
but this wont include the windows this is certain
now i’v never seen yet a rib vault arches script if youdo let us know!
may be one day will have one but not yet ! LOL
*) I’m building a model of a 12’th century church. Most of it is done, but the vaults are still missing.
*) No, I’m not certain about the circular arches:confused:. In fact, I think you’re right about the ogive type arches. I have no architectural training, and don’t know the technical terms. Could not find any arch-types that looked like the ones I’m making, but this is the one that came closest.
i think theses are ogive type arches not circular!
and for the time being i don’t know any rib vault script available yet
but may be Crouch will do one later on this year but not certain
if you want to see more on Arches read more about it in this post there are lot’s of
different type of arches describe and picture too that’s probably the most detail post you’ll find on arches and there is a scrip which is still a wip but you can do circular and parabola arches if you need it
Crouch told me that he would continue to add more type of arches soon
can you show some pics of what you have done up to now on your church or do you have another post for it may be?
it’s always interesting to see what models can come up on this forum
i have a wip somewhere if you search for church or may be in this post not certain where it is
i began doing a church with ogive type arches
but i stop cause i used to many verticies on my model and this was my first one
so one day i’ll do it again but being carefull to minimized the count of verticies
now i see that you did not do the arches with stone just a plain model
it does used less verticies but does not look as realist
but it’s a good model
now for the cross arches i would used the script shown earlier
just adjust the scale to fit you model and that’s it you got your crossing vault
dome - but there is no stones on that one
but still faster way to do it i guess
keep up the good work
you could open a WIP in the wip section and show bigger pictures and cross sections too should be interesting
I will post back here on the progress of the vault, but the general work will be at the above link. (no crossposting unless, offcourse, this is not considered crossposting)
