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From: shaun@attila.esa.oz (Shaun)
Newsgroups: comp.graphics
Subject: 3d Surface Patches
Keywords: patches, 3d
Message-ID: <415@attila.esa.oz>
Date: 12 Oct 89 03:12:11 GMT
Organization: esa
Lines: 61

Can anybody help with a classification scheme and explanation of 3d patch terminology.

1. Patches can be bilinear or bicubic

	I Understand this

2. Patches can be rational or nonrational 

	I Don't understand this

3. Patches can be uniform or non uniform

	I Don't understand this


4. Types of patches

	Bezier		(Understand)
	Spline		(Understand)
	Hermite		(don't understand)
	Power		(don't understand)
	CatmullRom	(don't understand)


5. Basis Matrices & Power Matrices

I know each bicubic has 2 4x4 matrices (one for U and one for V). I am a bit unclear
about the distinction between a power matrix and a  basis matrix. 
Also what is meant by 
	"a basis matrix that is used to transform from the power basis to the preferred basis ?".

6. Knots

What is meant by know values

7. Ducks

What are ducks.


I have a fair idea about most of the above, by have a little difficulty with some of the ideas and
terms used. I have read Foley & Van Dam, Newman & Sproull, RanKin, Rogers & Adams. Each explain
a little but none unify the concepts.

Also I have a specific question about texturing mapping and patch (U, V) interpolation. 
I want to group a IxJ array of similar type patches together and interpolate 
[U1 -> [0, 1], V1 -> [0,  1] across the entire array of
patches. I want to do this so that I can map a single unit square texture onto the entire
patch array surface, not just repeat the texture for each patch in the array.

I know that I have asked for a lot of information, but any help unifying concepts would
be appreciated.

	
Shaun Arundell: shaun@attila.esa.oz.AU (shaun%attila.esa.oz.AU@UUNET.UU.NET)
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-- 
Shaun Arundell: shaun@attila.esa.oz.AU (shaun%attila.esa.oz.AU@UUNET.UU.NET)
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