[Sidefx-houdini-list] First question to the list
David McBride
david00289 at yahoo.com
Wed Mar 10 18:52:15 EST 2010
it starts off with z^4 on the right. i subtracted z^4 from both sides. the node likes f=0
________________________________
From: Alex Czetwertynski <alex at franktheplumber.com>
To: sidefx-houdini-list at sidefx.com
Sent: Thu, March 11, 2010 1:00:11 AM
Subject: Re: [Sidefx-houdini-list] First question to the list
Thanks David
That is an awesome explanation! I can now generate all of those shapes!
If you wouldn't mind explaining one more thing....In this case, why
did the equal sign in the original equation become a minus in the
implicit function?
Thanks again, this is really fun
Alex
On Mar 10, 2010, at 2:26 AM, David McBride wrote:
> Alex,
>
> BTW, in the isosurface node those algebraic surfaces should go
> something like this:
>
> e.g. the Calyx, x2+y2z3 = z4 becomes $X*$X+$Y*$Y*$Z*$Z*$Z - $Z*
> $Z*$Z*$Z. Just enter it into the implicit function parameter window
> and you're done. No trig required hehe. Your (y4 - x4 + a y2 + b x2
> = 0) would just need some numbers of your choosing plugged in for a
> and b.
>
> best,
>
> david
>
>
>
>
> ________________________________
> From: Alex Czetwertynski <alex at franktheplumber.com>
> To: sidefx-houdini-list at sidefx.com
> Sent: Wed, March 10, 2010 4:14:42 AM
> Subject: Re: [Sidefx-houdini-list] First question to the list
>
> Thanks Andrew
>
> I was not able to get the formatting right, even by copy pasting into
> a text editor (I'm on a mac...), but I just recreated the network
> based and it worked fine.
>
> My knowledge of mathematics is probably too basic to understand
> exactly what is going on, as I was trying to figure out how I could
> plug the following cartesian equation
> (y4 - x4 + a y2 + b x2 = 0)
> into a similar setup, but have to admit I have no idea. Will go back
> to Trig 101 before I keep asking questions about this....
>
> Thanks for your help, at least I now have a nice Lituus curve!
>
> Alex
>
> On Mar 8, 2010, at 6:16 PM, Andrew D Lyons wrote:
>
>> This site is using mostly polar coordinates. Houdini uses mostly
>> cartesian coordinates:
>>
>> http://en.wikipedia.org/wiki/Polar_coordinate_system
>> http://en.wikipedia.org/wiki/Cartesian_coordinate_system
>> http://en.wikipedia.org/wiki/Polar_coordinate_system#Converting_between_polar_and_Cartesian_coordinates
>>
>> In any case to model something like this in Houdini you to set up
>> extra points to sample, and then do a conversion to cartesian as you
>> go. Take a look at the point SOP in this network: (Drop this script
>> in
>> a textport in Houdini - watch out for line wrapping from the email:)
>> ---------------------------------------------------------
>>
>> # Automatically generated script: Monday March 08, 18:11
>> \set noalias = 1
>> set saved_path = `execute("oppwf")`
>> opcf /obj
>>
>> # Node Lituus (Object/geo)
>> opadd -n geo Lituus
>> oplocate -x 3.69 -y 0.286303 Lituus
>> opset -S on Lituus
>> opparm Lituus use_dcolor ( off )
>> chautoscope Lituus +tx +ty +tz +rx +ry +rz +sx +sy +sz
>> opset -d on -r off Lituus
>> opexprlanguage -s hscript Lituus
>> opcf Lituus
>>
>> # Node file1 (Sop/file)
>> opadd -n file file1
>> oplocate -x 0 -y 0 file1
>> opset -d off -r off file1
>> opexprlanguage -s hscript file1
>>
>> # Node grid1 (Sop/grid)
>> opadd -n grid grid1
>> oplocate -x 11.8336 -y 5.95065 grid1
>> opparm grid1 rows ( 100 ) cols ( 1 )
>> opexprlanguage -s hscript grid1
>>
>> # Node point1 (Sop/point)
>> opadd -n point point1
>> oplocate -x 11.8668 -y 4.82124 point1
>> opparm point1 numcustom ( 1 )
>> chblockbegin
>> chadd -t 0 0 point1 tx
>> chkey -t 0 -v 0 -m 0 -a 0 -A 0 -T a -F 'cos(ch("weight"))*
>> 1/sqrt(ch("weight"))' point1/tx
>> chadd -t 0 0 point1 ty
>> chkey -t 0 -v 0 -m 0 -a 0 -A 0 -T a -F '$TY' point1/ty
>> chadd -t 0 0 point1 weight
>> chkey -t 0 -v 1 -m 0 -a 0 -A 0 -T a -F '$PI *($PT/18)*90' point1/
>> weight
>> chadd -t 0 0 point1 tz
>> chkey -t 0 -v 0 -m 0 -a 0 -A 0 -T a -F 'sin(ch("weight"))*
>> 1/sqrt(ch("weight"))' point1/tz
>> chblockend
>> opparm point1 t ( tx ty tz ) doweight ( on ) weight ( weight )
>> opset -d off -r off point1
>> opexprlanguage -s hscript point1
>>
>> # Node delete1 (Sop/delete)
>> opadd -n delete delete1
>> oplocate -x 11.8668 -y 3.86161 delete1
>> chblockbegin
>> chadd -t 0 0 delete1 rangeend
>> chkey -t 0 -v 0 -m 0 -a 0 -A 0 -T a -F '$N' delete1/rangeend
>> chblockend
>> opparm delete1 entity ( point ) pattern ( 0 )
>> opset -d off -r off delete1
>> opexprlanguage -s hscript delete1
>>
>> # Node null1 (Sop/null)
>> opadd -n null null1
>> oplocate -x 11.8668 -y 2.98478 null1
>> opset -d on -r on null1
>> opexprlanguage -s hscript null1
>> oporder -e file1 grid1 point1 delete1 null1
>> opcf ..
>>
>> opcf /obj
>> opcf Lituus
>> opwire -n grid1 -0 point1
>> opwire -n point1 -0 delete1
>> opwire -n delete1 -0 null1
>> opcf ..
>> opcf $saved_path
>>
>> ---------------------------------------------------------
>>
>>
>> Cheers
>>
>>
>> On 8 March 2010 17:35, Alex Czetwertynski <alex at franktheplumber.com>
>> wrote:
>>
>>> Hello
>>>
>>> This is my first post, been lurking around for a while...
>>> Been using Houdini for only a few months, so excuse the newbie tone
>>> of
>>> this question...
>>>
>>> I'm interested in using Houdini to create shapes of this sort
>>> http://xahlee.org/SpecialPlaneCurves_dir/specialPlaneCurves.html
>>>
>>> What would be the way to go about creating, say, a Lituus shape? It
>>> seems to me that the type of equation that is being used contains
>>> symbols that I have never seen in Houdini, but I could be wrong.
>>>
>>> Thanks!
>>> Alex
>>> _______________________________________________
>>> Sidefx-houdini-list mailing list
>>> Sidefx-houdini-list at sidefx.com
>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>
>>
>>
>>
>> --
>> =======================================
>> Andrew D Lyons | Digital Artist | http://www.tstex.com
>> =======================================
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>
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