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1 Tutorials LightWave 3D Texturing 101: Building Textures em Qua Jan 26, 2011 1:50 am

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by Gregory Duquesne


Introduction

Texturing
is a powerful and yet easy to use way to add
complexity to computer generated images. The
image to the left was created using only one
subdivided polygon, no drawings, nor photographs,
nor images of any kind, and this comes straight
from the renderer, no post processing applied.
All of the geometry, the distribution of the
rocks, the way snow sticks on the rocks, the
colors, etc... everything here is procedural,
which means that a few controls (on the procedural
function) are enough to describe this model,
and by adjusting some of these controls entire
new worlds can be created. It also means that
this model is very compact: the object is 2k
and the scene is 9k in size, making it easy to
manipulate, load, etc.

Texturing is no news for most
LightWave® users, they have been using displacement
textures, color textures, etc. since the very
early days of LightWave®. What's new with
LightWave® [6] is that the texturing paradigm
has been unified and extended to the entire application
including Modeler, this combined with the generalization
of subdivision surfaces and volumetric effects
in Layout is opening new ways to model that didn't
exist beforeTexture Layers
Textures are built upon 3 different components:


  • Images Maps
  • Procedurals
  • Gradients

Since these can be layered inside a texture
we call them texture layers. Each layer type
performs something very different:
<blockquote class="text_body">
Image maps:
<blockquote>
These are designed to apply an existing
image by choosing from different projections.
One of the major novelties with L[6] is the
UV projection which is described in more
details in other tutorials.
</blockquote>
Procedurals:
<blockquote>
They are functions which given a 3D coordinate
return a value, or a vector ( depending on
the evaluation context ). The new thing in
L[6] about procedurals is that they are now
implemented as plugins, so when a new plugin
is added it expands the choice of procedurals.
Another novelty is that all the procedurals
are available everywhere instead of being
restricted to certain areas as was the case
before.
</blockquote>
Gradients:
<blockquote>
These are new to LightWave®, they allow
the parametrisation of the textures. That
means that given some local parameters you
can change the appearance of the texture,
that's the way the snow was created in the
landscape image by using the "slope" parameter.
More on this important subject later.
</blockquote>
</blockquote>

Combining Layers
One of the most interesting benefits of layering
is that you can set different blending modes
between layers, this sets how one layer affects
the other. The blending modes are the following:


  • Additive
  • Subtractive
  • Difference
  • Multiply
  • Divide
  • Alpha
  • Texture Displacement

The first 5 modes are just different operators
on the layer outputs: A + B, A - B, A * B, A
B. Note that they are combined with the layer
opacity setting, so "additive" for instance is
only truly additive for an opacity value of 50%.
This is also how it used to work in previous
versions of LightWave®.
The 2 last modes are the most interesting in
terms of functionality:

Alpha Blending Mode
The Alpha mode allows to set any layer as an
alpha channel for the previous layer. The interesting
thing about it is that any layer can become an
alpha channel, therefore you can use an image
map as the color information and use a procedural
to set its transparency. Here is an example of
a texture that uses this functionality: Say we
want to make a texture that puts pink dots only
on the top of an object (more specifically in
the flat areas). To recreate this example, just
go to Modeler, create a box, open the surface
editor and add a texture to the color channel.
We set the first layer to be procedural (Layer
Type) and select "Dots" as the procedural type,
then we set the color to pink and adjust the
scale. This makes the base color texture:
<table align="center" border="0" cellpadding="0" cellspacing="0" width="160">
<tr>
<td></td>
</tr>
</table>
Now we had an additional gradient layer that
we set to use the slope (Input Parameter), and
we had keys so that the gradient goes from white
to black. As we can see on the sample sphere
this makes the surface white where it is flat
(that is on the top of the sphere) and black
where the slope increases:
<table align="center" border="0" cellpadding="0" cellspacing="0" width="160">
<tr>
<td></td>
</tr>
</table>
Now what we want is to have the original pink
dots show where the white is. We can do that
by simply setting the layer blending mode to "Alpha".
This produces the following result:
<table align="center" border="0" cellpadding="0" cellspacing="0" width="160">
<tr>
<td></td>
</tr>
</table>
What we have done here is say that the pink
dots should only affect the flat areas. This
looks trivial but it allowed us to create a relationship
between 2 layers and furthermore to relate texturing
to the geometry of the surface. The later point
will be examined in greater details later in
the next paragraph, suffice is to say for the
moment that it is one of the most powerful features
of the new texturing scheme.
Why exactly are the pink dots showing on the
top of the sphere ? That's because the gradient
is white on the top of the sphere, therefore
the alpha channel is white which means opaque,
so the previous layer (that is the pink dots)
will be show on the top. Similarly where the
gradient is black, the previous layer will be
transparent. You can try different colors for
the keys and see how their luminosity affects
the final result. Note that from there we can
do all kinds of modifications to the alpha channel
by inverting the layer, changing the opacity,
etc. all this will change the alpha channel and
the way it affects our nice little fuzzy pink
dots.

Texture Displacement
Mode

Texture Displacement is another interesting
blending mode. What it does is similar to the
displacements we can apply on objects, the difference
is that it only affects the internal texture
coordinates. Example: let's say we have a brick
layer that we like, but we want to add more detail
and randomness to it, unfortunately there is
nothing in the brick parameters that let us do
that. What if we could perturb one layer by another
a bit like we perturb a surface using bump ?
Well, that's what the texture displacement is
for. Here is the effect that we get by perturbing
a "brick" procedural layer by a "turbulence" procedural
layer:
<table align="center" border="0" cellpadding="0" cellspacing="0" width="160">
<tr>
<td></td>
</tr>
</table>
Note that the texture displacement layer must
be placed before the layer to displace. Also
note that the effect of displacement will propagate
to all the layers that follow. A way to understand
that is to think of the texture engine as a pipeline:
information is being carried over layer after
layer and affected by each layer, what this mode
is doing is just displacing the texture coordinates
the same way as a regular displacement would
distort an object's geometry, therefore all the
layers that follow will use distorted texture
coordinates which in turn will distort that pattern
they create.
Up Next: Texturing
102: Gradients & External Parameters
.
]

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