EnigmA Amiga Run 1995 November/EnigmA AMIGA RUN 02 (1995)(G.R. Edizioni)(IT)[!][issue 1995-11][Skylink CD].iso/earcd/docs/lwml9505.lha/LWML9505.TXT/[e-mail]_Mon May 22 08:37:56 1995.msg

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From: [e-mail] (James Hastings-Trew)
Subject: Re: Decals
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[e-mail] writes:

>        OK.  Now, how is the precedence of the effect determind?  To my ears,
>        it seems that there must be some kind of implicit or explicit alpha
>        channel defining how the each texture affects the previous texture.

Bitmap textures can be "told" to ignore colour 0... obviously this only
applies to indexed colour images (8bits and down). Colour 0 is then
"transparent" so that the colour of the previous texture is unchanged.
Procedural textures usually modify the colour of the previous texture --
modification meaning anything from "do nothing" to "completely replace" at
any given point on the surface. Most procedural textures in Lightwave and
Imagine take the base colour of the object and do something to it in some
sort of non-uniform way across the surface. For example, the wood texture
in Lightwave takes the base colour of the object and applies another colour
to it in a wood-grain pattern. Take that a step further, and imagine that
the "base colour" is whatever the last texture did to the surface, and
you'll see how it works.

>        And, of course, how is it placed?  In TrueSpace, you can see a rep-
>        resentation of the bitmapular  :^)  rectangle.

Imagine represents the bitmap as a cubic volume, which has a fairly
intelligent guess at where you'd like to place the bitmap (covering the
entire object). Since each type of mapping requires a different position of
the texture map cube, Imagine will default to giving a "standard" placement
depending on what kind of map projection you want. Imagine does not call
its projection options anything as obvious as "flat" or "spherical" or
"cylindrical" but instead makes you figure out which axis you'd like the
map to be flat in, and which axis to 'wrap' the map around.

You can move, rotate, skew, scale, and stretch the mapping volume in
Imagine. This is a really cool feature that I wish Lightwave had. For
example, have a look at my "treekit" objects (on LightROM 1 I believe). I
created the same objects for Imagine and for Lightwave. Due to the
shortcomings of Lightwave's mapping options, I had to build the trees as a
heirarchy of objects which were mapped and then rotated into position. In
Imagine, the objects were built as a single object, and the mappings
themselves were rotated into position instead. Much easier to build and
manage the object.

Having said that, I have not had that much trouble with Lightwave mapping,
and careful planning and forethought is all that is needed to get the
effects I want. I really like the diffuse and specular mapping (which
Imagine does not have). The mapping options would not be enough to get me
to switch back to Imagine.


--
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