Texturing

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TUTORIALS |
Textures for realism
ON THE WEB
●
The tutorial fi les are in
the Stop Press section of
www.3dworldmag.com
Getting dirty
Life, as everyone knows, is dirty. It’s the accurate simulation of years of grime, scratches and contact with the
physical worlds that can lend some essential realism to an otherwise pristine, antiseptic model
BY STEFAN MORRELL
ften it’s the small details like scratches, scuff
marks and dents that lend a certain realism
to even the most fantastic objects. In fact,
the everyday wear and tear that can only be
re-created with a careful mix of hand-painted textures
and photographic reference can be the thing that really
makes or breaks a model.
In this tutorial, we’re going to take an otherwise pristine droid
and give it a good visual thrashing. Imagine it is battle-scarred from
years of confl ict and abuse: we need to create the tell-tale signs of
everyday life. Its edges are faded and worn, scratches in exposed
areas have been fi lled with ground in dirt, and recessed areas have
become clogged up and decals have decayed over time.
It is often these touches that can make your model shine, adding
character to an otherwise lifeless object. And knowing where the
scratches, grazes and grime will be most effective can be an artform
in itself.
Using scene fi les available on the
3D World
website, we will
begin by using the Render to Texture dialog to render an Ambient
Occlusion (MR) map. This is used throughout the texturing process,
both as an aid in knowing where to paint (and where not to) and
as a mask for fi lling new layers. This map can be multiplied above
the texture, offering free ambient occlusion without any extra
render overhead. It’s a technique commonly used in game texturing,
where real-time ambient occlusion would be too expensive to use
otherwise. We will also look into using a scratch brush to roughen up
the edges of the model. While the brush itself is important, painting
these scratches should be done in a very loose fashion, as if you
were roughly scribbling on paper.
We will create a base texture, followed by colour fi lls that use
the Use All Layers function in
Photoshop
, an often overlooked
feature that can quickly and effectively add much-needed variation
to a texture.
Finally, we’ll create a greyscale bump and refl ection/specular
map using a modifi ed version of the colour texture. Layers and the
blending options in
Photoshop
will help us create a hard-surface
texture that looks like it’s seen many years of use, and interacts with
lighting and shaders as you’d expect an object to in the real world.
FAC TFILE
FOR
3ds Max
DIFFICULTY
Intermediate
TIME TAKEN
Three hours
ON THE WEB
• Scene fi les
• Textures
• Screenshots
ALSO REQUIRED
Photoshop
Stefan Morrell is a freelance digital artist living and working
in New Zealand
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Textures for realism
| TUTORIALS
STAGE ONE |
Rendering an ambient occlusion map
EXPERT TIP
Render to texture
Take time to explore the options in the
Render to Texture dialog. Rendering
different elements can be a great help
when it comes to texturing: if we had,
for example, parts laid out onto a UV
template, we could assign colours to
each part and render a diffuse map.
Then the colour could act as a mask in
Photoshop
. The benefi t of rendering
an occlusion map is to bake an
expensive rendering effect into the
texture. This way, you no longer need
to use the more expensive rendering
option. When laying out your UVs, try
to avoid overlapping faces: these will
appear as black in your baked texture..
Load up the droid_start.max scene with
3ds Max 8
.
This scene contains a droid model that is UV mapped
and ready for texturing. However, before baking an
ambient occlusion map, we need to change the render engine
from the default scanline to
mental ray
. Press [f10] and scroll
down to Assign Renderer. Click the Production box and assign
mental ray
as the renderer.
With ‘hullfront’ selected, open the Render to Texture
dialog (Render > Render to Texture) and, under the
Output rollout, select Add > Ambient Occlusion (MR).
Change the map size to 1024 and Samples to 32: the default
of 16 will render faster, but 32 will offer a fi ner result. Now
create a path to save the rendered image and hit Render.
STAGE TWO |
Creating the basic texture
While in
3ds Max,
we can render a UV template that
can be used as a guide when painting in
Photoshop
.
With ‘hullfront’ selected, add a UVW modifi er
(Modifi ers > UV Coordinates > Unwrap UWV) and in the
modifi er options, click Edit. With the Edit window open, select
Tools > Render UVW Template, and set both width and height
to 1024. Click Render UV Template and save the image.
Open the occlusion map and template in
Photoshop
,
copy the template onto the occlusion map and
change its Blending Mode to Screen. Change the
opacity of the Occlusion layer to 35%, then create a new layer
and fi ll it with 50% gray (R:128; G:128; B:128). Name this
layer ‘Base’, and make sure it is below the Occlusion layer. The
template should be at the top of the stack.
Create a layer called ‘Scratches’. With the Brush tool
selected, press [F5] to open Brush Options and select
‘Chalk 11 pixels’ from the Brush Tip Shape dropdown.
Activate Shape Dynamics if you have a tablet, select Scattering
and apply the values: Scatter: 209% (Both Axes, Pen Pressure
Control); Count: 4; Count Jitter: 36% (Control Off). Activate
Texture with the default settings, and select Wet Edges.
Set the Scratches layer to Screen, and scribble the
lines in very quickly and roughly. Imagine you’re
rough-sketching something with a pen and paper.
They have to look natural and unplanned, after all. These lines
are to simulate aging and general wear and tear along exposed
edges of the droid, so keep them loose. They’ll also be used
later for both bump map and fl ood fi ll masks.
Because you want to paint these scratches in logical
areas, such as along exposed edges, it’s a good idea
to have the
3ds Max
scene open, with an Unwrap
UVW modifi er applied and the Edit window open. You can now
select faces of the model and see what parts of the texture
they correspond to when viewing the UVs.
Create a new layer called Grime and, using any soft
brush, lightly paint in some dirt along areas that
might be expected to collect it. Apply a 10% vertical
motion blur to the layer, then paint over the grime again using
a slightly darker shade and a smaller brush. Apply the same
motion blur, change opacity on this layer to around 80% and
set the Blend Mode to Overlay.
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TUTORIALS |
Textures for realism
STAGE THREE |
How to create aged paint
EXPERT TIP
All Layers
The All Layers option can be very
effective at quickly creating aged
paint. The way it reads the contrast of
all the layers means you can control
where paintwork may be aged and
worn away from everyday exposure.
With our texture, we’ve assumed the
edges of the droid are more worn, and
the contrast offered by the Scratch
layer means any fl ood fi lls we apply
will avoid that area. All Layers can be
used with several
Photoshop
tools and
can create various effects. It’s also a
good idea to keep this effect as subtle
as possible, because it’s very easy to
overdo things.
Open photosource_Concrete.jpg and copy it to a new
layer called ‘Grunge’. Set the Blend Mode to Soft
Light and change opacity to 25 per cent. Turn off the
Template layer. Now create a new layer called Paint and select
the Bucket Fill tool, check the All Layers option and apply the
fi ll. These fi lls are affected by the contrast of all the other
layers, so the scratch edges are not receiving any fi ll. To have a
more subtle effect, raise the Tolerance value.
Create a new layer below the Paint layer and call it
‘Undercoat’. Hold [Ctrl] and click on the Paint layer.
This will make a selection based on the previous
paint fi ll. Expand this selection by two pixels (Select > Modify
> Expand) and, with the Undercoat layer selected, fi ll with a
darker shade (R:124; G:88; B:6). You won’t need the All Layers
option selected for this fi ll.
STAGE FOUR |
Hullfront textures
Refer back to your
3ds Max
scene with the UVW
Editor open, and ensure you’re selecting the right
areas for this step. We want to put a stripe of colour
around the edge of the droid, so select faces in the UVW editor
and see which parts of the model they correspond to – the red
areas in the screenshot.
In
Photoshop,
create a new layer called ‘PaintColour’
and select the soon-to-be red band. Turn All Layers
back on and fi ll the selection with red. Move this new
layer above the Occlusion layer. Open Decal.psd, select the
Barcode layer and drag it to your hullfront texture. Position
it on the droid and change its Blend Mode to Multiply. Do the
same with the other decals, using the Normal blend mode.
Make a selection of the ‘eye’ part of the template
– refer to the UVWs in
3ds Max
to ensure you’re
selecting the correct area – and, with the Base layer
active, use levels to darken this area (Image > Adjustments
> Levels). Save the selection for later use (Select> Save
Selection). This process will add variation to the texture. For a
little more detail, add some text to the circular part of the lens.
Add an Adjustment layer at the top of the layer
stack and call this ‘Global Colour’ (Layer > New
Adjustment Layer > Color Balance), following the
values in the screenshot to create a global colour adjustment
to all the layers in the stack. Save a copy of the .psd fi le
before fl attening all the layers. Add a small amount (25%) of
sharpening and save the image as ‘hullfi nal_colour.tga’.
Open the previously saved layered .psd, which we
will use to create the greyscale bump map. Select the
Scratches layer and invert it (Image > Adjustments
> Invert), then change the Blend Mode to Multiply. Select the
PaintColour layer and desaturate it (Image > Adjustments >
Desaturate) before adjusting the brightness so that the Paint
Colour layer is brighter than the Paint Fill layer.
Desaturate and adjust the brightness of the
Undercoat layer so it is slightly darker than the
Paintfi ll layer, then reload the selection saved earlier
(Select > Load Selection). Adjust the brightness of the Base
layer – ensuring it’s light enough that the Scratches layer can
be clearly seen. Invert the selection and lower the brightness
of the Base layer so it is darker than both Paintfi ll layers.
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Textures for realism
| TUTORIALS
STAGE FOUR (Continued) |
Hullfront textures
[Ctrl]+click the Danger decal layer and create a new
layer. Fill this selection with a shade that is slightly
lighter than the Paint Fill layer, which should help to
sell the decal as a sticker on the surface on the model. Raise
the opacity of the Grunge layer to 70% and convert the image
to greyscale (Image > Mode > Greyscale). Save as ‘Hullfront_
Bump.tga’ and ‘Hullfront_Bump.psd’.
Using the same layered .psd, we can create a specular
map. Select the Scratches layer, set Blend Mode to
Screen and invert it back to white: this will ensure
this part of the model receives the most highlights. The rule
with a specular map is that whatever is light will create strong
highlights and whatever is dark will receive less: think about
where dirt might collect for added realism.
Lower the opacity of the PaintColor layer to 7% and
PaintFill to 35%. The Scratches layer should be the
brightest of all here but, essentially, we are trying
dull down all the layers so there’s not too much contrast. If you
want more refl ection below the paint work, make the Base
layer brighter. Lower the occlusion opacity to 20% and save
this fi le as ‘Hullfront_Spec.tga’.
STAGE FIVE |
Wrapping up
Each of the main templates are painted using these
techniques. The eye of the droid was done using
a simple shape created with the selection tool in
Photoshop
and applied to the self-illumination Material slot in
3ds Max
. This is a pretty quick way to add a cool sci-fi feel to
the fi nal scene.
Smaller elements on the model such as bolts, screws
and vents can be dressed with a generic tiling
texture. This makes template creation easier, and
saves time laying out UVs for parts that are rarely seen. Import
photosource_rust.jpg, and play around with it using fl ood fi lls
with All Layers. Save the result as a Pattern fi ll for quick access
(Edit > Defi ne Pattern).
To see the fi nal settings, open the Droid_Final.max
scene. You can examine how each texture map has
been applied to the model using the Material/Map
Navigator. The high contrast of the greyscale bump map
means bump strength should be kept fairly low in this
instance, suggesting grazes rather than gouges. Lighting has
also been kept fairly low-key, with the exception of some
omni lights placed inside the model to create a subtle sci-fi
interior effect. For added realism, use the specular map as a
refl ection mask, remembering that anything light on the map
will cause more refl ection and dark areas will show less. You
could even add some HDRI in your rendering if you have the
time and horsepower. Try using the specular map as a mask
for the HDRI refl ection.
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