2d interval

hi,

i thougt that a 4 point surface with u:1, v:1 has the same intervals , as the lenght of the sides. hope u understand what i mean, the ghx should point it out ...

thanx for the help

Attachments:

2dinterval.ghx, 65 KB

Replies to This Discussion

Permalink Reply by David Rutten on December 10, 2009 at 5:11pm

Hi Dcay,

The length of which sides? The average length? Intervals do not carry useful information regarding size or shape of an object. They are merely two numbers that define the range of the valid parameter space. You can change the U and V intervals of any surface using the _Reparameterize command without affecting the shape in any way.

Curves and surfaces are given an interval at the time of creation and it is up to each command to determine what that initial interval should be. Most commands will pick intervals that roughly correlate to the physical dimensions, but there are also commands that will create intervals based on control-point-count.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by dcay on December 10, 2009 at 5:32pm

thanxs for responding,

"They are merely two numbers that define the range of the valid parameter space."

ok so where does the numbers come from ?
if i have a surface for i input in the divide interval2 component it gives me for example something like
u{0.0 to 100} v{0.0 to 200}
so what does this 0.0 to 200 say about my surface ?

Permalink Reply by David Rutten on December 11, 2009 at 2:25am

The numbers come from nowhere special. Nowhere important. They say nothing about your surface. You can change the numbers without affecting your surface, and you can change your surface without affecting the numbers.

Someone of course has to invent these numbers when the surface is created from scratch, but they are free to use any numbers they please, provided they are different numbers for the lower and upper limit.

Most often, it is easiest to work in the unit range (0.0 to 1.0) and there's an option in the menu of all curve and surface parameters that allows you to normalise the domain by reparameterising the existing domain to the zero-one range. Sometimes however it is important to maintain arbitrary intervals, which is why we don't always reset the domain to zero-one whenever the geometry changes.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

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