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30 Jul 2024 18:18:19 EDT (-0400)
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From: sumdumguy
Subject: How to add a bump to an object?
Date: 17 Nov 2008 17:20:00
Message: <web.4921ed67475bbc133b34ecfe0@news.povray.org>
I am stuck with the following problem: I have an egg-shaped object and I want to
pull on it locally, deforming it. I want the deformation to affect the entire
shape. The easiest way to visualize it is to think of an egg with a plastic
shell and liquid inside. Now bring a match close to one spot on the egg,
locally softnening the plastic and allowing water to bulge out the shape.
One approach would be to do a blob. However, blobs are too local and they only
work with spheres and cylinders not splined lathe objects like my egg shape.
Is there a way to programmatically add a bump to an object in a particular
direction?


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From: Mike Williams
Subject: Re: How to add a bump to an object?
Date: 18 Nov 2008 00:14:29
Message: <w85TYvBS0kIJFwau@econym.demon.co.uk>
Wasn't it sumdumguy who wrote:
>I am stuck with the following problem: I have an egg-shaped object and 
>I want to
>pull on it locally, deforming it. I want the deformation to affect the entire
>shape. The easiest way to visualize it is to think of an egg with a plastic
>shell and liquid inside. Now bring a match close to one spot on the egg,
>locally softnening the plastic and allowing water to bulge out the shape.
>One approach would be to do a blob. However, blobs are too local and they only
>work with spheres and cylinders not splined lathe objects like my egg shape.
>Is there a way to programmatically add a bump to an object in a particular
>direction?

I reckon that there are two basic approaches, neither of them easy.

You could model your egg as a smooth mesh and calculate the changes to 
the vertices and normals as the shape changes.

You could model your egg as an isosurface and do isosurface blobbing 
http://www.econym.demon.co.uk/isotut/combine.htm#blob
Hint: if you want a real egg shape, rather than just an ellipsoid, you 
can use non-linear scaling on a sphere
http://www.econym.demon.co.uk/isotut/substitute.htm

-- 
Mike Williams
Gentleman of Leisure


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From: sumdumguy
Subject: Re: How to add a bump to an object?
Date: 18 Nov 2008 01:35:00
Message: <web.492261d42924023d3b34ecfe0@news.povray.org>
Thanks. The latter works great albeit slow.


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