POV-Ray : Newsgroups : povray.advanced-users : mesh2 cut off Server Time
1 Nov 2024 05:20:04 EDT (-0400)
  mesh2 cut off (Message 1 to 2 of 2)  
From: gregjohn
Subject: mesh2 cut off
Date: 27 Oct 2007 19:30:00
Message: <web.4723c8d63337baa434d207310@news.povray.org>
I was trying to make a mesh2 that looks like this: imagine a goldfish bowl with
a conical funnel glued to it.  The "circle" of the goldfish bowl is congruent
with the large "circle" of the funnel, with the funnel poking back up inside it
rather than being a "hat".

I used a macro of my creation to extrude a mesh2 into this shape. A problem-- a
feature-- of my mesh2 is that the normals all point away from the center line
of the object. They are "correct" for the bowl portion but pointing the wrong
way for
the funnel portion.

Odd thing is that when I render it, it looks like the opening of the goldfish
bowl is closed off as if I had put a flat cylinder there.

Now I know that it something might be unseeemly in a structure where the normals
are messed up. But I wouldn't have expected my messing with the laws of nature
to close off the shape.  Have I interpreted what I'm seeing correctly?


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From: Jan Dvorak
Subject: Re: mesh2 cut off
Date: 28 Oct 2007 02:29:24
Message: <47243a54$1@news.povray.org>
gregjohn napsal(a):
> I was trying to make a mesh2 that looks like this: imagine a goldfish bowl with
> a conical funnel glued to it.  The "circle" of the goldfish bowl is congruent
> with the large "circle" of the funnel, with the funnel poking back up inside it
> rather than being a "hat".
> 
> I used a macro of my creation to extrude a mesh2 into this shape. A problem-- a
> feature-- of my mesh2 is that the normals all point away from the center line
> of the object. They are "correct" for the bowl portion but pointing the wrong
> way for
> the funnel portion.
> 
> Odd thing is that when I render it, it looks like the opening of the goldfish
> bowl is closed off as if I had put a flat cylinder there.
> 
> Now I know that it something might be unseeemly in a structure where the normals
> are messed up. But I wouldn't have expected my messing with the laws of nature
> to close off the shape.  Have I interpreted what I'm seeing correctly?
> 
> 
> 
> 
> 
1) look at the lathe object. It does exactly what you want.
2) as far as I know POVray does no backface culling unless you use 
interior_texture. Are you sure there is no flat face where you expect 
your mesh2 (e.g. water)?
3) please post your rendering in the pov-ray.binaries.images or post a 
link to the image here. Also please post your pov-code.
4) also, don't forget you need a closed object if you want to use 
refraction.


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