Try

new Vector4d(0.0, 1.0 , 0.0,  -JsliderValue * extremumPointTop  ); //
(the plane will be parallel to the xz plane)

Assuming  the JsliderValue is between 0 and 1.

The eqation of a plane in 3d space is

0 = ax + by + cz + d. In the vector4d you specify the a parameters
a,b,c,d.

To get a feeling what this equation describes take some simple examples:

a = 1, b = 0, c = 0, d = 0 -> 0 = x : the plane is defined as all points
with x coordinate  = 0 that is the yz plane.

a= 1, b = 0, c = 0, d = 1 -> 0 = x + d -> -d = x: the plane is defined
as all points with x coordinate  = -d that is the yz plane translated
along the x axes about -d.

With the parameters 0,1,0 -jsliderValue * extremum the equation reads as

y = jSliderValue * extremum. The defimed half space which points are
rendered is then y <= jSliderValue * extremum that mean all points with
an y value <=
jSliderValue * extremum are rendered.

Olivier Tassy schrieb:

> Hi,I have a Jslider(values 0 to 100%) wich performs a modelclipping
> for a set of objects in my scene.I want the clipping to start from the
> top point of the top object and finish to the bottom point of the
> bottom object.I can get the coords of both extremum by using
> BoundingBox'  getUpper and getLower methods (thank you Joachim), but I
> don't know how to set the plane equation for the ModelClip. I tried
> with something likeVector4d eqn1 = new Vector4d(0.0, extremumPointTop
> , 0.0,  -JsliderValue * extremumPointTop  );modelclip.setPlane(1,
> eqn1); But it seems to be wrong.  Thanks for your help in advance.

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