[Sidefx-houdini-list] First question to the list

David McBride david00289 at yahoo.com
Wed Mar 10 05:26:41 EST 2010


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
>> _______________________________________________
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>> 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
> =======================================
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