modeling statue

[maxopus]

I have said several times that subds are not used for industry, although many cads are incorporating them (magari come tsplines) to facilitate initial design. But it is also true that the subds are not nurbs or bezier's principles, I do not know which of the two approaches more, if someone has the basis to explain it to him.
Moreover alias if not erro is based on nurbs and industrial design is quite used, so maybe for the subd there are other "nicchies". but said all this, if I had to shape a human figure with bezier surfaces, well I think I would rather give myself to the hyppic :d

maxopus but in fact why the nurbs are not accepted? nothing religious wars for charity is only to understand better I hope indeed that all 'I despair about the subds that I have done is not understood as a war of religion :

Palo

I'm also discussing it to better understand. :smile:
I think bezier curves and surfaces are used because they are the best controllable ones.
to get an idea of their definition on wikipedia the topic is treated pretty well at the following link: http://it.wikipedia.org/wiki/curva_di_bézierapart from the headache that you will come to try to understand the mathematical concept, reasoning to the peasant, it is understood that they have the advantage of being manageable through control triangles.

any contribution to deepen the speech is very welcome :smile:

 

[zpaolo]

However, when you wrote that for human models "chissenefrega" of the curvature, my hair has been removed and in the sewer I have escaped the hyperbole beyond the sign , but I am interested simply to understand how much of the surface that is recreated with the subds etc should then be "lised" during rendering or animation.

My fault I misunderstood the term "curvature", I did not mean continuity, but the precise value. in the cad you make a 1mm ray and it is a radius of 1mm, there are no saints. with subds you can get a perfect fillet but you will never know how much the curvature will be. at the same time being the "skin" under unique and united, probably the continuity of curvature is very but very high. therefore you will not have "specs" in the flow of reflections, but the "fluidity" with which the reflections run on such a surface is to be understood, depends on how many points of control you have, how they are arranged etc., the risk is not to have broken reflections but "the drafts".

So you wouldn't do it because the quality of the surface to be sent to the molder so that he can make chips for a milionata of euro in mold :tongue: is it not acceptable or for other reasons?

I wouldn't do it because "for now" and in the software I know subds simply aren't a "design" tool: I can't set constraints, measures, it's a "scultorea" thing, so very suitable for organic models, but not controllable (which doesn't mean the results suck, only then it's hard to put hands on it)

interesting...only that seems the head of the stone man of the fantastic4:smile:, which then rendered softens (it is however obscene also rendered). Maybe I'm wrong, but that kind of model is extremely rough.

You're wrong, losing the purely artistic aspect (I think it was the head of a troll, handling 'the Nordic modelers :d ) is not that it softens when it is "rendered": when you see it "soft" is because the operator has pressed a button that converts the model from polygonal to subd. or: first it has a rough polygonal model, made by few polygons precisely, then the "convert" in subd, each vertex becomes a point of control of a mathematical surface that stands below. the model so obtained is very "smooth", and it is always changeable both through the control points (which usually the modelers hide at this stage) and jumping "towards and back" from the polygonal mode. to understand the softness you see then is not due to some algorithm of normal mapping or shading, it is the new surface. If a modeling kernel supports this kind of math you might well import it.

I also watched other similar movies made with other software (mudbox, zbrush, 3dstudio etc) and I think the principle is the same. few polygons smoothed after in rendering or during modeling by opengl shading in real time, just to understand the final result that will be rendered.

they are not smoothed by shading, what you see is a new surface. considers a spline curve defined through control points, it is a continuous curve and "liscia", controlled by a series of vertices. the polygonal line "greaty" that controls the spline in this case is a rough polygonal model that controls the subd. is not very different from the control vertices of a surface in the cad, but here the topology of these vertices is defined by the user (i.e. I can add and remove them where they serve).
zbrush and mudbox work very differently, and are aimed at producing a sculptural model with "absurd" details, but with light weight, let's say that for now they come out of discussion

but I go back to ask you, because this is the point that was interested in the famous ass: can you export an iges so that when I open it in solidworks (I am glad that it is worthy to do so :smile see it with a beautiful smooth surface and with zebra cone imbizzarrite :wink:

the "you can" do if solidworks or who for it supported the "direct" reading of the subds, or could import them without first tiling them. I don't know if it's possible, and I don't know if there is only one subd implementation (catmull clark is almost universal anyway), so the official answer to your question is "I don't know, but in theory yes" :d

Palo

 

[zpaolo]

I'm also discussing it to better understand. :smile:
I think bezier curves and surfaces are used because they are the best controllable ones.
to get an idea of their definition on wikipedia the topic is treated pretty well at the following link: http://it.wikipedia.org/wiki/curva_di_bézier

ok, but I have to see it for good, only a note though, just to increase the intrinsic headache: in English wikipedia under the heading "nurbs" appears the same image of the yacht that I see on the page you have linked :d and on the same page http://en.wikipedia.org/wiki/nurbs says that the nurbs were used "initially only by the cad owners of the car companies"

but apart from this, to give an idea of the concept of subd, we take a bezier curve of high order, therefore with a number of points of control. if the "extrude" you can think of having a lattice of control points that generates the surface below. when using the free form deformation in pro|e or solidworks you can change this lattice. subds are the same thing at the operational level, only that it is easier to make changes to the lattice (type add points, extrude parts) and more difficult trimmarle (at least in the software I know). I do not know if there is a difference in the relationship between the control points and the surface below between bezier, nurbs and subd, I think so.

Palo

 

[zpaolo]

for those interested in the whole story, this document is very interesting:
http://www.cl.cam.ac.uk/techreports/ucam-cl-tr-773.pdfamong other things one interesting thing is how the process of subds is "hytherapeutic" and only to the infinite converge on a limit surface, but in fact the various software already show the limit surface _prima_ of the tile:

in the image there is a cube, defined with the usual 6 polygons, and transformed into a subd, the green figure that is seen is what in the document mentioned before is called "superficie limit" of the subd, the intermediate passages just do not see.

Palo

 

[zpaolo]

the nurb surfaces are not accepted by industry, if they have to realize a car body shop or the hull of a motorcycle.
the only accepted surfaces are beziers and on this there are no alternatives.

just to try to deepen, I found a lesson: http://personales.unican.es/iglesias/cd-cg/bsplines.pdf It is not that it is very discourse unfortunately, but the quite important thing is that the curves (or surfaces) of bezier turn out to be a "subset" of the curves nurbs, and to what I know most of the kernels of the cad take advantage of the nurbs to have maximum flexibility.
then surely it is "better" to work with curves in a certain way, the concept of class surfaces to is based more on how to use curves and surfaces that not on the mathematical definition that stands at the base (for example, better a curve that has two vertices and tangency vectors rather than a curve with three vertices of control), but I think we are a little bit shattered by the dead Christ of the subject :d

Palo