Ramp interpolation

[Noti]

Although I don't expect to get an answer, I still want to ask:

what kind of base function is used for the B-spline interpolation of ramp panel in Houdini.

Because as shown in the figure below, the shape I draw with vex according to the B-spline basis function is basically the same as that of the convert node, but this result is different from that of the B-spline in the ramp panel. And i found that the curve shape of the ramp panel is better to use.

The biggest difference is the position of the extreme point of the curve. I drew it in blue.

So I would like someone to indicate what base function (or method) is used by the B-spline of the ramp panel in Houdini?

[anim]

you can use PolySpline SOP

set Spline Type to BSpline

and First/Last CV count to 2

[Noti]

11 hours ago, anim said:

you can use PolySpline SOP

set Spline Type to BSpline

and First/Last CV count to 2

Hi, thanks.

It does achieve the same result as ramp, but what I want to know is what interpolation formula it uses (Bspline).

Because i want to use it outside houdini.

[Aizatulin]

Hi,

have you checked "De Boor's algorithm" ?

https://en.wikipedia.org/wiki/De_Boor's_algorithm

It seem to give similar result if you add 2 additional start and 2 additional end points.

The weights are all 1 and the knots uniformly distributed.

Here is an experimental file

 

 

deBoorTestC.hipnc

[Noti]

1 hour ago, Aizatulin said:

Hi,

have you checked "De Boor's algorithm" ?

https://en.wikipedia.org/wiki/De_Boor's_algorithm

It seem to give similar result if you add 2 additional start and 2 additional end points.

The weights are all 1 and the knots uniformly distributed.

Here is an experimental file

 

 

deBoorTestC.hipnc

My god! You gave me a lot of inspiration.

Just add two more points at both ends.

Thanks a lot and share my code here, you can see some differ（want to buy you a drink haha）.

deBoorTestC.hipnc