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I believe this is possible to do with isosurfaces - I'm just not very good
at them :s
I need something like a sine wave extruded in the +z direction
If I have:
f(x) = sin(2*pi*x)
how do I get that into something like corrugated roof? I've read the
excellent tutorial on isosurfaces <http://www.econym.demon.co.uk/isotut/>
and can copy/paste as well as the next man but am obviously missing
something as I don't seem to be able to do what I need
As always, any input is greatly appreciated!
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Simon wrote:
> If I have:
> f(x) = sin(2*pi*x)
>
> how do I get that into something like corrugated roof?
Simon,
The cross section of a corrugated roof will be 2D, so you will need data
for at least two axes when making your roof. Here is an example:
function{
y // Makes a y-facing surface.
+cos(2*pi*x)/4 // Distorts surface by adding one x-oriented wave
// per unit, scaled by 0.25.
}
~Sam
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Thanks very much for that :) That actually makes sense :)
I'd gone off on a tangent and actually came up witha macro to make a mesh
froma given function - I'll compare the 2 to match parse times/render
times. Also, I expect the isosurface will have a higher quality...
Again, thank you!
~S
"Samuel Benge" <stb### [at] THIShotmail com> wrote in message
news:4677e60d$1@news.povray.org...
> Simon wrote:
>> If I have:
>> f(x) = sin(2*pi*x)
>>
>> how do I get that into something like corrugated roof?
>
> Simon,
>
> The cross section of a corrugated roof will be 2D, so you will need data
> for at least two axes when making your roof. Here is an example:
>
> function{
> y // makes a y-facing surface
> +cos(x*pi*2)/4 // distorts surface by adding one x-oriented wave
> // per unit, scaled by 0.125
> }
>
> ~Sam
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Wasn't it Simon who wrote:
>I believe this is possible to do with isosurfaces - I'm just not very good
>at them :s
>
>I need something like a sine wave extruded in the +z direction
>
>If I have:
>f(x) = sin(2*pi*x)
>
>how do I get that into something like corrugated roof? I've read the
>excellent tutorial on isosurfaces <http://www.econym.demon.co.uk/isotut/>
>and can copy/paste as well as the next man but am obviously missing
>something as I don't seem to be able to do what I need
Mathematically, what you want to plot is y=f(x)
I.e y = sin(2*pi*x)
But isosurfaces evaluate expressions of the format
<function> = <threshold>
where threshold is a constant, so we rewrite the expression as
y - sin(2*pi*x) = 0
isosurface {
function { y - sin(2*pi*x) }
max_gradient 4
contained_by{sphere{0,5}}
pigment {rgb 1}
}
We dont need to bother saying "threshold 0" because that's the default.
--
Mike Williams
Gentleman of Leisure
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That is very clear! Thanks Mike - If you don't mind some further
questions...
Say we wanted to do something like an infinitely long crinkle-cut chip
(excuse the awful description)
Dealing with 1 dimension at a time...
y<1+sin(x*2*pi)
y>-1+sin(x*2*pi + pi/2)
how can I combine the 2? - to be more precise, how do I define the "solid"
bit as the area between the two?
If you'd rather point me at a tutorial and leave me to it, I understand but
if you're willing to walk me through this, I'd greatly appreciate it
Thanks in advance!
NB I've used the sine wave isosurface for the curtains in an animation I'm
posting in p.b-a if you're interested.
"Mike Williams" <nos### [at] econymdemoncouk> wrote in message
news:Vbj### [at] econymdemoncouk...
> Wasn't it Simon who wrote:
>>I believe this is possible to do with isosurfaces - I'm just not very good
>>at them :s
>>
>>I need something like a sine wave extruded in the +z direction
>>
>>If I have:
>>f(x) = sin(2*pi*x)
>>
>>how do I get that into something like corrugated roof? I've read the
>>excellent tutorial on isosurfaces <http://www.econym.demon.co.uk/isotut/>
>>and can copy/paste as well as the next man but am obviously missing
>>something as I don't seem to be able to do what I need
>
> Mathematically, what you want to plot is y=f(x)
>
> I.e y = sin(2*pi*x)
>
> But isosurfaces evaluate expressions of the format
> <function> = <threshold>
> where threshold is a constant, so we rewrite the expression as
>
> y - sin(2*pi*x) = 0
>
> isosurface {
> function { y - sin(2*pi*x) }
> max_gradient 4
> contained_by{sphere{0,5}}
> pigment {rgb 1}
> }
>
> We dont need to bother saying "threshold 0" because that's the default.
>
> --
> Mike Williams
> Gentleman of Leisure
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Wasn't it Simon who wrote:
>That is very clear! Thanks Mike - If you don't mind some further
>questions...
>
>Say we wanted to do something like an infinitely long crinkle-cut chip
>(excuse the awful description)
>
>Dealing with 1 dimension at a time...
>
>y<1+sin(x*2*pi)
>y>-1+sin(x*2*pi + pi/2)
>
>how can I combine the 2? - to be more precise, how do I define the "solid"
>bit as the area between the two?
>
>If you'd rather point me at a tutorial and leave me to it, I understand but
>if you're willing to walk me through this, I'd greatly appreciate it
>
>Thanks in advance!
You can use this trick to do two dimensions at once
http://www.econym.demon.co.uk/isotut/substitute.htm#thick
Like this:
function { abs(sin(2*pi*x)-y)-0.25 }
To do four directions, you can use max() to perform the intersection of
the simpler functions.
#declare F = function(x,y) {0.1*sin(2*pi*x)+y}
isosurface {
function { max( F(x,y-1), F(x-0.5,-y-1), F(x,z-1), F(x-0.5,-z-1)) }
max_gradient 1.2
contained_by{box{<-5,-2,-2><5,2,2>}}
pigment {rgb <0.9,0.8,0.7>}
}
--
Mike Williams
Gentleman of Leisure
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