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The image gives some test examples that use fat Bezier patches, made up of fat
strips. fat fans, fat triangles or fat quadrilaterals.
The arrowhead is a single fat Bezier triangular patch (with its reflection) with
a hollow cylinder attached to one of the vertices. The Starck Juicer was the
subject of a recent set of posts. The body is mainly sphere sweeps (of a single
Bezier segment variety - I like the control) The legs are two fat strips.
I like the knife, which needs two fat fans, three fat strips - one specifically
the transition region.
The glasses are produced with a glass making #macro, using the sphere blends and
hollow roundcone.
The #macros in use do need e.g. eight vectors and eight radii for a strip, ten
for a triangular patch and sixteen for a quadrilateral patch. Challenging, but
not impossible for an object using very few patches - the seat and back of the
chair are each made of a single quadrilateral patch.
For static objects, there may be no advantage (and a disadvantage of needing
good 3D visualisation to input the co-ordinates and radii) over a modeller.
However, it is possible to parameterise some of the co-ordinates or radii to
simply change a shape, as in the next post to this thread.
Post a reply to this message
Attachments:
Download 'fat_bezier_test_examples.png' (193 KB)
Preview of image 'fat_bezier_test_examples.png'
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The wings are made of two quadrilateral patches and a triangular patch. One
quadrilateral patch blends to the fuselage, the second forms the main wing. The
triangular patch forms the wingtip.
Changing a single parameter allows for the wing to curve upwards when providing
lift.
The tail is a single fat triangular patch with a hollow roundcone for the intake
differenced for the exhaust. Any differences have to be done as locally with
the patch definition as possible - the numbers of objects in a patch mean a
difference with a union of many patches with take forever to render.
Lucky clipka is working on parse. Parse time was 31 seconds, render time 8
seconds at 1024x768.
I've posted these to see if there is enough interest for me to either post code,
bugs and all, or spend (quite a bit of) time cleaning it up and uploading to
objects.
I've tried to see if a human figure is possible. It sort of is, but parametric
posing is difficult, and I must be doing the clothing wrong, since that has been
very difficult. I will go back to see how POVPerson did it.
Post a reply to this message
Attachments:
Download 'fat_bezier_reaper.png' (108 KB)
Preview of image 'fat_bezier_reaper.png'
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hi,
"JimT" <nomail@nomail> wrote:
looks all very impressive, I really like the office chair.
> I've posted these to see if there is enough interest for me to either post code,
> bugs and all, or spend (quite a bit of) time cleaning it up and uploading to
> objects.
I'd love to see the code for the shapes of your first post, hope you can post.
regards, jr.
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Am 29.05.2018 um 16:14 schrieb JimT:
> Everyone is familiar with the roundcone, a convex object, and the sphere sweep
> derived from it.
Is everyone?
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On 29/05/2018 20:06, clipka wrote:
> Am 29.05.2018 um 16:14 schrieb JimT:
>> Everyone is familiar with the roundcone, a convex object, and the sphere sweep
>> derived from it.
>
> Is everyone?
>
Not me, for one.
--
Regards
Stephen
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Le 18-05-29 à 15:06, clipka a écrit :
> Am 29.05.2018 um 16:14 schrieb JimT:
>> Everyone is familiar with the roundcone, a convex object, and the sphere sweep
>> derived from it.
>
> Is everyone?
>
I do know about the tree versions, but don't remember using them.
Two with spherical ends and one with flat caps with a rounded connection
with the side.
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> I've posted these to see if there is enough interest for me to either post code,
> bugs and all, or spend (quite a bit of) time cleaning it up and uploading to
> objects.
>
Thanks Jim, this is an interesting idea.
I made some trials on the same idea although my computations were the other way
round : from the three spheres, let say in the horizontal plane, I first
computed the 2 tangent planes to the three spheres, the one above the spheres
and the one below. From the 6 tangency points, we get 6 lines. Grouping these
lines by pair, we get 3 cones. More specifically, in the middlee of each pair is
a line through the centers of 2 spheres, and the corresponding lathe object
around the middle line is the cone to be added.
This construction shows if I am not wrong that the cone is tangent to the plane,
so I did not understand your C1-problems in your first message.
My goal was much more simple than what you did. I just wanted to draw rounded
boxes with different radius along the edges.
Post a reply to this message
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"lelama" <nomail@nomail> wrote:
> > I've posted these to see if there is enough interest for me to either post code,
> > bugs and all, or spend (quite a bit of) time cleaning it up and uploading to
> > objects.
> >
>
> Thanks Jim, this is an interesting idea.
>
> I made some trials on the same idea although my computations were the other way
> round : from the three spheres, let say in the horizontal plane, I first
> computed the 2 tangent planes to the three spheres, the one above the spheres
> and the one below.
I accept your argument. Three spheres will have a pair of tangent planes and if
you join two of the tangent points, you have a line with two identical normals
at the ends which must be a generator of the tangent cone. The fat triangle
therefore has to be C_1 and the apparent discontinuity is all to do with
discontinuity of curvature.
Coming from the tangent cones direction, I didn't see why the two tangent points
had to be on a single generator of the tangent cone and assumed they weren't.
Checking in an actual example:
Nor21 = <-0.59960801,-0.05058799,0.79869336>
Nor22 = <-0.59960801,-0.05058799,0.79869336>
Nor23 = <-0.59960801,-0.05058799,0.79869336>
that is, three identical normals to 8 dp. So, thanks, I now realise the smooth
triangles are not needed - ordinary triangles or a pair of transformed prism
objects will do (a prism would help with CSG intersections and differences).
Simplifying the construction of a single fat triangle should have an effect on
the speed of parsing - which would be a help since it is slooow.
>From the 6 tangency points, we get 6 lines. Grouping these
> lines by pair, we get 3 cones. More specifically, in the middlee of each pair is
> a line through the centers of 2 spheres, and the corresponding lathe object
> around the middle line is the cone to be added.
>
> This construction shows if I am not wrong that the cone is tangent to the plane,
> so I did not understand your C1-problems in your first message.
>
> My goal was much more simple than what you did. I just wanted to draw rounded
> boxes with different radius along the edges.
I've added an image with the triangles in a different colour. I initially
expected the edges to be subtly curved, which they are not. Printing out the
three normals is a confirmations.
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clipka <ano### [at] anonymous org> wrote:
> Am 29.05.2018 um 16:14 schrieb JimT:
> > Everyone is familiar with the roundcone, a convex object, and the sphere sweep
> > derived from it.
>
> Is everyone?
Round_Cone, Round_Cone_Union, Round_Cone_Merge and Round_Cone2 and Round_Cone3
variants are in shapes.inc from John vanSickle.
Not that I am familiar with everything in the include files. I constructed a
round cone #macro before I was informed about the shapes.inc version. I wanted
it to use in a single Bezier segment version of a sphere sweep that would cope
with the sphere radius going negative by coming to a point, being absent while
the radius was negative, and then starting up again from a point.
I guess most people are familiar with the sphere sweep.
Anyway, thanks to isama, I am now happy to assert the fat triangle is C_1, and
go away to simplify the code.
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"lelama" <nomail@nomail> wrote:
Sorry, I've just got a new pair of glasses and misread your name. Maybe I should
go back to the optician.
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