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I am pretty New to Povray and use Moray as well to generate scenes. But I
have a problem with the bicubic_patch.
What I wanted to do is generate a flat bicubic_patch where the start control
points are all at the same position. But it seems I loose the entire rounded
side and only display one the triangle. Even bringing the points close
This is the code I have
object { // BezPtch001
object {
bicubic_patch { type 1 flatness 0.0100 u_steps 3 v_steps 3,
<1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
<1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
<-2.000000, -1.000000, 0.000000>, <-1.000000, -1.000000, 0.000000>,
<0.000000, -1.000000, 0.000000>, <1.000000, -1.000000, 0.000000>,
<-2.000000, 0.000000, 0.000000>, <-1.000000, 0.000000, 0.000000>,
<0.000000, 0.000000, 0.000000>, <1.000000, 0.000000, 0.000000>,
<-2.000000, 1.000000, 0.000000>, <-1.000000, 1.000000, 0.000000>,
<0.000000, 1.000000, 0.000000>, <1.000000, 1.000000, 0.000000>
}
}
material {
Material2
}
translate 1.0*z
}
Bizarly enough moving some of the inner pounts up along the Z axis does
solve my problem for the most part. Like this.
object { // BezPtch001
object {
bicubic_patch { type 1 flatness 0.0050 u_steps 3 v_steps 3,
<1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
<1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
<-2.000000, -1.000000, 0.000000>, <-1.000000, -1.000000, 0.200000>,
<0.000000, -1.000000, 0.200000>, <1.000000, -1.000000, 0.200000>,
<-2.000000, 0.000000, 0.000000>, <-1.000000, 0.000000, 0.200000>,
<0.000000, 0.000000, 0.200000>, <1.000000, 0.000000, 0.200000>,
<-2.000000, 1.000000, 0.000000>, <-1.000000, 1.000000, 0.200000>,
<0.000000, 1.000000, 0.200000>, <1.000000, 1.000000, 0.200000>
}
}
material {
Material2
}
translate 1.0*z
}
Am I just stupid? Or is this normal? And if so Why?
Napivo
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I'm not sure what shape you want it to be, but 2 of your corner points are
in the same place. The points in a bicubic patch follow this order:
A, B, C, D,
E, F, G, H,
I, J, K, L,
M, N, O, P
You can imagine that's a top-down view of the patch, the points A D M and P
are the corners, all the ones in between are control points. In yours A and
D have the same position <1.000000, -2.000000, 0.000000>, hence it appears
triangular.
A simple square one would be:
<0,0,0>, <1,0,0>, <2,0,0>, <3,0,0>,
<0,1,0>, <1,1,0>, <2,1,0>, <3,1,0>,
<0,2,0>, <1,2,0>, <2,2,0>, <3,2,0>,
<0,3,0>, <1,3,0>, <2,3,0>, <3,3,0>
That might be an easier thing to start with. Note the control points are
evenly spread between the corners so you get a nice distribution of polygons
when pov processes the patch. Also I wouldn't bother using flatness, it's
not really necessary unless your patch is really slow to draw.
--
Tek
http://evilsuperbrain.com
"Napivo" <Nap### [at] yahoo fr> wrote in message
news:web.45a761af6f5b502e3cd9c0860@news.povray.org...
>I am pretty New to Povray and use Moray as well to generate scenes. But I
> have a problem with the bicubic_patch.
>
> What I wanted to do is generate a flat bicubic_patch where the start
> control
> points are all at the same position. But it seems I loose the entire
> rounded
> side and only display one the triangle. Even bringing the points close
> together doesn't solve my problem.
>
> This is the code I have
>
> object { // BezPtch001
> object {
> bicubic_patch { type 1 flatness 0.0100 u_steps 3 v_steps 3,
> <1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
> <1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
> <-2.000000, -1.000000, 0.000000>, <-1.000000, -1.000000, 0.000000>,
> <0.000000, -1.000000, 0.000000>, <1.000000, -1.000000, 0.000000>,
> <-2.000000, 0.000000, 0.000000>, <-1.000000, 0.000000, 0.000000>,
> <0.000000, 0.000000, 0.000000>, <1.000000, 0.000000, 0.000000>,
> <-2.000000, 1.000000, 0.000000>, <-1.000000, 1.000000, 0.000000>,
> <0.000000, 1.000000, 0.000000>, <1.000000, 1.000000, 0.000000>
> }
> }
> material {
> Material2
> }
> translate 1.0*z
> }
>
> Bizarly enough moving some of the inner pounts up along the Z axis does
> solve my problem for the most part. Like this.
>
> object { // BezPtch001
> object {
> bicubic_patch { type 1 flatness 0.0050 u_steps 3 v_steps 3,
> <1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
> <1.000000, -2.000000, 0.000000>, <1.000000, -2.000000, 0.000000>,
> <-2.000000, -1.000000, 0.000000>, <-1.000000, -1.000000, 0.200000>,
> <0.000000, -1.000000, 0.200000>, <1.000000, -1.000000, 0.200000>,
> <-2.000000, 0.000000, 0.000000>, <-1.000000, 0.000000, 0.200000>,
> <0.000000, 0.000000, 0.200000>, <1.000000, 0.000000, 0.200000>,
> <-2.000000, 1.000000, 0.000000>, <-1.000000, 1.000000, 0.200000>,
> <0.000000, 1.000000, 0.200000>, <1.000000, 1.000000, 0.200000>
> }
> }
> material {
> Material2
> }
> translate 1.0*z
> }
>
> Am I just stupid? Or is this normal? And if so Why?
>
> Napivo
>
>
>
>
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Thanks,
I posted a message at http://docs.google.com/View?docid=dk65p6z_6cpkdtv to
demonstrate what I was trying to do. It works now as I decided to curve
the deck of the ship. This is more realistic anyhow.
But I still find it odd that a flat bicubic_patch gives me a rectangle while
a curved one curves in both directions.
I will not worry about it any longer. For me the problem is solved.
Thanks for your time
Napivo
"Tek" <tek### [at] evilsuperbraincom> wrote:
> I'm not sure what shape you want it to be, but 2 of your corner points are
> in the same place. The points in a bicubic patch follow this order:
>
> A, B, C, D,
> E, F, G, H,
> I, J, K, L,
> M, N, O, P
>
> You can imagine that's a top-down view of the patch, the points A D M and P
> are the corners, all the ones in between are control points. In yours A and
> D have the same position <1.000000, -2.000000, 0.000000>, hence it appears
> triangular.
>
> A simple square one would be:
> <0,0,0>, <1,0,0>, <2,0,0>, <3,0,0>,
> <0,1,0>, <1,1,0>, <2,1,0>, <3,1,0>,
> <0,2,0>, <1,2,0>, <2,2,0>, <3,2,0>,
> <0,3,0>, <1,3,0>, <2,3,0>, <3,3,0>
>
> That might be an easier thing to start with. Note the control points are
> evenly spread between the corners so you get a nice distribution of polygons
> when pov processes the patch. Also I wouldn't bother using flatness, it's
> not really necessary unless your patch is really slow to draw.
>
> --
> Tek
> http://evilsuperbrain.com
>
// Message Truncated //
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Napivo nous apporta ses lumieres en ce 12-01-2007 08:19:
> Thanks,
> I posted a message at http://docs.google.com/View?docid=dk65p6z_6cpkdtv to
> demonstrate what I was trying to do. It works now as I decided to curve
> the deck of the ship. This is more realistic anyhow.
> But I still find it odd that a flat bicubic_patch gives me a rectangle while
> a curved one curves in both directions.
> I will not worry about it any longer. For me the problem is solved.
> Thanks for your time
> Napivo
There is nothing "strange" about a flat bicubic_patch to apears as a rectangle.
There are 4 base points and 12 equidistent control points, all coplanar, this
can't make anything but a rectangle unless two base points are merged into one
changint it into a triangle.
--
Alain
-------------------------------------------------
I'm so ugly I stuck my head out the window and got arrested for Mooning.
Rodney Dangerfield
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If anyone stumbles across this problem, the solution is to set the flatness
parameter to zero (the default value).
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