Function gets it's math wrong ?

In the attached files, both calculation results output by functions are wrong.
Did I miss something about functions ?

Attachments:

Wrong_Math.ghx, 75 KB

Replies to This Discussion

Permalink Reply by Vicente Soler on August 11, 2009 at 10:39am

Don't use 'e' as the name of a variable. Grasshopper think's you're trying to use the mathematical constant e.

Permalink Reply by Olivier Suire on August 11, 2009 at 11:09am

GOT IT !!
Thanks Vicente.
Now this is pretty nasty : there should be big flashing warnings about this...

Permalink Reply by Vicente Soler on August 11, 2009 at 11:31am

Don't give David ideas for new icons to draw.

Permalink Reply by David Rutten on December 1, 2009 at 1:59am

The new version of Grasshopper has overwritable variables. First, all the constants (e, pi, phi etc.) are declared, but if you then decide to use a variable of your own called e, pi or phi, the value will replace the constant.

--
David Rutten
david@mcneel.com
Leusden, Holland

Permalink Reply by Leonid Krykhtin on November 29, 2009 at 4:12pm

Hello Vicente!
Could you explain how to create math surfaces using functions components if I have a function expression.
I take the math function expressions from Wolfram's website and write them inside of a GH function component. But have no idea how to proceed. What components do I need to input/output to a function component?

Permalink Reply by Vicente Soler on November 29, 2009 at 4:37pm

Hi,
First you need to know the parametric equations and the uv domain you want to represent.
For example, i want to create an Enneper surface, i know the parametric equations are:
x = u*cos(v)-u^3/3*cos(3*v)
y = u^2*cos(2*v)
z = -u*sin(v)-u^(3)/3*sin(3*v)

and the domain i want to display is:
u: 0 to 1
v: -PI to PI

One way of creating this surface would be like this:

The expression component must be set to "cross-reference".
Although it doesn't look pretty, to simplify the definition i concatenated the 3 equations using the syntax to create directly a point from an expression component, this is "{x,y,z}".

Permalink Reply by Leonid Krykhtin on November 30, 2009 at 12:56pm

Vicente,
Thanks a lot for your explanation.
I haven't got the logic of building that kind of definition.
Why do we need the Addition component?
Why did you input 20 to the Range components?
Why did you input 1 to the Addition component?
What if I don't have u and v variables but have only x, y, and z variables like in a Schwarz IsoSurface:
-(cos(x)+cos(y)+cos(z))
where x: -4 to 4,
y: -4 to 4,
z: -4 to 4.

Thanks in advance.
Leonid

Permalink Reply by Vicente Soler on November 30, 2009 at 1:22pm

What the definition does is to create a grid of points in 3d space that corresponds to the shape of the surface, then i interpolate a surface through these points.

20 is the resolution of the surface. If i divide an interval in 20 steps, i end up with 21 numbers, so i'm creating a grid of points that consists of 21 x 21 points. Since the surface component asks for the number of points in the U direction, i get the number "20" and add 1 to end up with 21.

If you want to create an isosurface, it's not as easy since the points can't be arranged into a grid. You can display the boundary points of the surface easily but to create actual geometry you need something like a marching cubes algorithm. I did a definition for it but it works really slow. An alternative can be to bake the points and use rhino's mesh from points command.

Permalink Reply by Leonid Krykhtin on November 30, 2009 at 2:45pm

Thanks very much.
I will try to experiment.

Permalink Reply by Chris K. Palmer on November 30, 2009 at 4:15pm

Hi Leonid,

Here is a definition I made awhile back to make several common parametric surfaces. It is of course quite similar to the one Vicente made. Many paths to the same goal!

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