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Art of Illusion modelling tutorial - the hourglass
http://www.artofillusion.org/docs/hourglasstut/[5/12/2015
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Art of Illusion modelling tutorialthe hourglass
Version 1.2For Art of Illusion version 2.9
Copyright 2001 Rick van der MeidenChanges copyright 2011 Peter
Eastman
Introduction
In this tutorarial you'll be shown how to model a simple object
with Art of Illusion (AoI), using as an example the hourglass in
the pictureabove. This tutorial does not cover all the feature
found in the AoI modeller, there are simply too many, but enough to
get you started. Youwill propably figure out the rest by simply
trying, experimenting, creating cool graphics.
If you are already familiar with 3D modelling, you will propably
not need to follow this tuturial step by step. You might leaf
through it to getsome idea of the program's capabilities, but
please go and just try it out yourself. For you newbies: I'll get
you going making your own 3Dgraphics in just a few minutes.
For the sake of completeness, an AoI scene file called
"hourglass.aoi" is distributed with this tutorial that you can
simply open with themodeller. However, if you want to learn from
this tutorial, you should try building the scene yourself.
Look around
Lets assume that you've downloaded the whole bunch of AoI,
you've got the right JDK version, read the readme files, and got
the thing going.If not, refer to the Art of Illusion home page.
When you start AoI, you are presented the main screen. On top of
the window is your basicmenu bar; take a look around, see what's in
the pulldowns. If there's a lot up there that you don't understand,
don't worry. You will in time.
To the left you see some icons. Clicking them selects a tool and
a single line of help is displayed at the bottom of the screen. The
icons are:
move object rotate object
resize object move/resize/rotate object
create box create sphere
create cylinder create spline mesh
create polygon create curve
create camera create light source
move view rotate view
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Art of Illusion modelling tutorial - the hourglass
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The bulk of the screen displays four views on the 3D model:
Front, Left, Top and Camera1. For each view the user can set a
camera orstandard viewpoint (front, left, top, etc.), perspective
or parallel viewing mode, display mode (wireframe, shaded, etc.),
and a zoom factor(default 100). These viewpoints can be changed
using the two appropriate tools for movement and rotation. You will
often change the scaleand position of these views but not the
viewpoint. The standard views are quite sufficient for most
modelling sessions. Only the lower rightview, Camera1, will be
changed often because it's very useful for checking out the
model.
On the right is a (now empty) space for showing a list of
objects (shapes) in your model. From this list you can select or
deselect objects byclicking on their names. Also, double-clicking
will bring up the edit-object dialog.
Before getting started, you need to know about one more thing:
coordinates. The positions and dimensions of objects are determined
by acoordinate system with three axes, named X, Y and Z. The X axis
is considered to be pointing to the right, that is: the greater the
Xcoordinate of a point, the more to the right it is in the model.
Likewise, the Y axis points upwards and the Z axis points out of
the screentowards you. (In jargon this is called a right handed
coordinate system)
Getting started
It's commonly considered good practice to start a 3D modelling
session by first sketching your model on grid paper, to get some
idea of itsdimensions and shape. If you don't, then at least set up
a grid in the modeller:
select Scene->Grids from the menuset Spacing to 0.5set
Subdivisions to 10check Show grid and Snap to gridclick OK
This allows us to easily draw objects with an exact position and
size and to align objects othogonally. You may change the grid
parameters atany time to accomodate your needs for finer or coarser
grids. Now let's start drawing. First draw a box for the wooden top
and bottom of thehourglass frame:
select the 'create box' tooldraw a box of 1.5 units wide and 0.1
units hight in the front view. That is, with a grid of 0.5 units
and 10 subdivision, 3 gridlines wideand two subdivisions high.
select the 'resize object' toolscale the object in the top view
until it is square, 1.5 by 1.5 units.
select the 'move object' toolmove the box so it is centered in
the top view.move it in the front view so it is just below the
second grid line from the center.check out the box's coordinates in
the Properties panel at the bottom right of the window. The box
should be sized 1.5 units on the Xaxis, 0.1 units on the Y axis,
and 1.5 again on the Z axis. It should be positioned with its
origin at coordinate (0, -1.05, 0). From thispanel you can change
the box's size, position, orientation, and other properties (see
figure below).
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Art of Illusion modelling tutorial - the hourglass
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Notice that you can draw any object in either the front, left or
top view. Since you can only draw two dimensions at once, you'll
have to set athird dimension afterwards. You may use the scale and
move tools for changing the position and size of the box. But if
you have a clear ideaof what the dimensions should be, the
Properties panel is much quicker.
The first box is the bottom of the model. The top looks exacly
the same, so create a box for it by copying.
select the first box, Cube 1 from the list on the rightselect
Edit->Copy from the menuselect Edit->Paste from the menumove
the copy upwards until the bottom of the box is at y=1. Do this by
using either:
the 'move object' tool. Hold shift to move only orthogonal.the
Properties panel. Center it at y=1.05.the Object->Transform
Object option from the menu. Move it 2 units upwards on the Y
axis.the Object->Align Objects option from the menu. Align the
bottom (y-axis) to 0.
Now we have two boxes, symmetrical about the origin. Note that
both boxes are still named Cube1. You can change the name of the
selectedobject in the Properties panel. Proper names could be 'Top'
and 'Bottom'. Now it is easier to keep them apart when selecting
from the list.
Using the techniques above we can also create the four poles
between the top and bottom boards. Use the 'create cylinder' tool
tocreate a cylinder of the following proportions:
position: X = 0.6, Y = 0, Z = 0.6size: X = 0.05, Y = 2, Z =
0.05
And create three more cylinders in the other corners of the
hourglass frame. Hints:
draw the first cylinder in the front or left view, this allows
you to set it's diameter as well as its length. Position the
cylinder using theother views.Create the other cylinders by copying
and moving.You cannot see the cylinders you've created in the top
view because they are obscured by the top box. Select
Scene->Display Mode->Wireframe from the menu, and you will be
able to see them again.
Now we have a frame for the hourglass. Now use the 'move
viewpoint' tool and the 'rotate viewpoint' tool to change the
lower-right view (camera1). Now you can see the model from any
angle you like. The result should look something like this:
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Art of Illusion modelling tutorial - the hourglass
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A complex object
The most complex shape in this scene is the glass bulb. It will
be created using the Lathe tool. A lathe is an object created by
revolving a
spline curve, which determines the contour of the shape, around
an axis. To create the contour curve we will use the create curve
tool.To avoid painfully precise mouse work, first create a finer
Grid: spacing 0.2 with 2 subdivisions. Then select Scene->One
View from themenu. You can then set the zoom factor of the view to
200 percent. Now create the spline curve by adding the points 1
though 9 shown in theimage below (in that order). Double-click
point 9 to finish the spline curve. Make sure that the first and
the last point are nicely on the y axisand tangent to the the top
and bottom boxes we made earlier.
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This is an approximated curve, meaning the curve does not pass
exactly through all the points. You can also create interpolated
curves, where
the curve does pass through all the points. Double-click the
create curve icon to pick which kind of curve to create. The
approximatedcurve is less intuitive, but produces a smoother shape
than the interpolated curve does. The direction of the curve at the
beginning and end ofthe curve is determined by the only adjacent
point. The curve is vertical at point 5 because points 4 and 6 are
both vertically displaced fromthis point. In general, the curve at
any point is determined by the immediately preceding and following
definition points.
As the central axis of the glass bulb, we will use the line
running though the endpoints of the curve. In our drawing, this is
the y axis, but byusing the first line results in a solid object.
To create the lathe, first select the curve and then select
Tools->Lathe from the menu. In the lathedialog, select the Line
though endpoints as the lathe axis (see figure below).
The lathe shape is automatically centered at (0, 0, 0). This is
exactly where we want it, so leave it. (Of course this is no
coincidence. I plannedit that way!). The spline curve that we
created first is now redundant. You may delete it, but you don't
have to since it won't show up in thefinal rendering. To delete an
object, select it (from screen or from list of objects) and press
delete on the keyboard. You may also use themenu option
Edit->Clear.
Scene layout
Now we've finished modelling all the shapes. We should try to
render the scene with accurate shapes and lighting. Before
rendering though,we should determine the layout of the key elements
in the scene, the camera and the light.
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Art of Illusion modelling tutorial - the hourglass
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First, determine the position and orientation of the camera.
This is easily done using the camera preview in the lower right
corner. Translate
and rotate the view using the move view tool and the rotate view
tool. Hold Control while moving the view to zoom in and out.
And you may roll the view over by holding Control and using the
rotate view tool. You may also position the camera using the
move
object tool and the rotate object tool or with the Properties
panel. The camera is an object just like any other. A good position
mightbe one where you can see the top and two other sides of the
object.
Next we should illuminate the scene. As you can see there is
already a light source in the scene from the beginning of the
session, Light 1.The light source should be positioned so that it
illuminates the side of the object we are looking at. Light 1 is
probably not positioned correctlygiven the position of the camera.
Since this light source is also far away, we'll delete it and
create a new one. AoI supports three types of lightsources: point
lights, directional lights and spot lights. We'll use the simplest
of them, the point light. Follow the next steps to
correctlyilluminate the scene:
Find a position for the new light near the camera or at least on
the same side of the object as the camera. Use a lower zoom factor
(30)to find the camera in the views.
To create the light, click on the create light source icon and
click over the position where you want the light. You
shouldprobably move the light (just like moving other objects) in
one of the other views to get the correct position in 3D space.We
should change some properties of the light source to accomodate its
position relative to the hourglass. You can do that with
theProperties panel, as shown in the image below. The default
Intensity value is a bit high, resulting in a picture that looks
like thecamera was blinded by the light. Change the intensity value
to 0.8. Set the Decay Rate to zero. This value determines how fast
lightintensity decays over distance. In reality, light intensity
decay is related to the squared distance. The default Decay Rate
would result ina very dark image. This simple scene does not need
this much realism anyway, so let's make things easy and turn it
off.
Now let's render. Select Scene->Render Scene from the menu.
Don't bother with the settings yet, just press OK on the render
dialog. Theresult should be something like this:
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Art of Illusion modelling tutorial - the hourglass
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Rather boring isn't it ? Everything is a dull white. We want
wood and glass, we should add textures.
Textures and materials
Wood
Let's create a texture that looks like wood. Select
Scene->Textures from the menu to display the Textures and
Materials dialog. Find thepopup menu that says New... (in the top
right corner of the dialog) and select Procedural 3D texture.
3D procedural textures determine color, roughness, reflection
and other surface properties as a function of 3D coordinates. For
any position inspace, the texture defines what a shape's surface
looks like, as if we had cut the shape out of a solid block of this
'material'. However, forobjects of which we can actually see the
inside, transparent objects, we should use a material to define the
inside, not a texture. Texturesonly determine what the surface of
an object looks like.
A function mapping 3D coordinates to the values of texture
properties is created by graphically connecting functional
components. There aresix categories of components:
Values determine a color or value that may be used as input for
other values.Operators are simple mathematical operations like
addition and subtraction.Functions output scalar values that depend
on their inputs.Color functions output color values that depend on
their inputs.Transforms transform coordinates to a new set of
coordinates.Patterns determine a scalar value as a function of
coordinate values. This scalar value may be used to determine a
color pattern for thetexture or to pattern some other texture
property.
When you've created a new texture, you'll be presented with a
dialog in which you may specify the texture. There's a large empty
white area,in which we'll add functional components. And to the
right there are blocks with names like diffuse, specular,
transparent, etc. These areproperties of a texture which will be
connected to the components we've added in the empty area.
The following components are added to the procedure to make a
wood texture:
Select Patterns in the menu on the left side of the window to
display the Patterns category, then click on Wood. This is a
pattern ofconcentric cylindrical bands along the Z axis, just like
the cross-section of a tree trunk has concentric rings of color.
The default inputsof this components are the three coordinate
values, X, Y, Z and a 0.5 noise value. These are fine, so we won't
have to add componentsfor them.We'll use this pattern for the
diffuse color of the texture. Select the Color Functions category
in the menu, then click on Custom.Connect the wood pattern
component to the custom color function, and connect the color
function to the diffuse color component at theright of the dialog
(see figure below). Now you should see rings appear on the preview
image.
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Art of Illusion modelling tutorial - the hourglass
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Next we should add some nice woodish colors to the texture. To
do this, double-click the custom color function component. You'll
bepresented with the dialog below. Add extra markers (little
trangles) and set the color at each triangle to match the colors in
the dialogbelow.
Finally, we'll make the wood texture a bit denser, more rings.
Double-click the wood pattern component and set the values shown in
thedialog:
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Art of Illusion modelling tutorial - the hourglass
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The preview now looks like this:
The texture doesn't really look very realistic but it will have
to do for now. To create more complex textures, read the section on
textures ofthe the Art of Illusion manual.
This texure will be assigned to the top and bottom boards and
the sticks in between that we've created earlier. Select all the
shapes that shouldbe assiged the Wood texture. Then select
Object->Set Texture and Material from the menu. Now select the
Wood texture and press OK.
Now select only the Top and Bottom objects. Again call up the
set texture dialog. Now click on the button labeled Edit Mapping.
In thisdialog, you may scale, translate, and rotate the texture to
fit the object. We'll only rotate the texure to get the following
result:
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Art of Illusion modelling tutorial - the hourglass
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Now for the sticks. Select them all and edit the mapping mapping
again. Create a mapping like this:
Now let's look at the result. The rendered image will look
something like this:
Glass
The glass bulb object should have the material properties of
glass. That is, it should should be transparent to light and it
should also reflectlight on the surface. Light that passes through
a glass object is refracted and attenuated (e.g. diminished, change
of color). Reflection andtransparency are texture properties.
Refraction and attenuation are properties of an object's material.
Materials can only be assigned to solidobjects. This makes sense
because the amount of attenuation and direction of the light after
refraction depends on where a ray of light entersand on where it
leaves the object. Fortunately, our bulb shape is a solid object.
All lathed shapes with the rotation axis through the begin-
andendpoints of the profile curve are solids.
First we'll create the glass texture, and then the glass
material.
Select the bulb. From the Texture option in the Properties
panel, select New Uniform Texture. This texture will make the
surfacetransparent, so the inside material will be visible, and it
determines the amount of specular reflection. The image below shows
what settingsto use for the new texture. Transparency is controlled
by both the Transparent Color and the Transparency value. The red,
green and bluefraction of the transparent color determine how much
of each color component remains when light passes though the
surface. It is a filter
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color. White, the default color, means that light of any colors
passes the surface. Black means no light passes. The transparency
valuedetermines the total fraction of the light that passes though.
A value of 0.7 means that 70 percent of the light is let through
the surface. Thisalso means that the transparent component
determines the color of the surface for 70 percent. The remaining
30 percent of color will bedetermined for 100 percent by
reflection, so the Specular value will be set to 1.0. Shininess
determines the brightness of reflected highlights.In most cases,
specularity and shininess should be set to the same value. The
surface's diffuse component does not affect the total color
withthese settings. We'll use the object's material to color the
glass.
To create a new material, select New Uniform Material for the
Material option in the Properties panel. The new material may also
benamed Glass. You can see the parameter settings in the image
below. The color of a material is affected by three parameters:
Emissive Color,Transparent Color, and Scattering Color. Emissive
color is the color of light given out by the material. Use this for
glowing materials likefire. Our glass shouldn't glow, so this is
set to black. Transparent color affects the light passing through
the object, and also colors theshadows cast by the object. It
specifies the fraction of red, green and blue that passes through.
Scattering color is the color of light that getsreflected from
inside the object. How much the light is attenuated is determined
by the Density value. A value of zero results in noattenuation. For
this glass material we'll specify a green scattering color that
only shows on very massive objects.
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Art of Illusion modelling tutorial - the hourglass
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The final rendering
The default black background makes the glass material look odd.
To improve the aprearence of the glass, we'll set a bright
background. SelectScene->Environment from the menu. In this
dialog, Environment is already set to Solid Color. Click on the
color box just below it, andchange it to white.
Finally, to improve the image quality, set Antialiasing to
Maximum in the render dialog. And if your light source is near the
object, checkingSoft Shadows will result in a more realistic image.
Both options cause the raytracer to cast multiple rays per pixel.
The results are averaged tocreate a smoother image. Setting the
minimum and maximum number of Rays/Pixel to higher values results
in better image quality andslower rendering speed. For a quick
image, don't use these options. Good quality is achieved by setting
minimum and maximum to 4 and 16rays respectively. More rays may be
needed for large soft shadow areas.
Raytracer settings and the resulting image are shown below:
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Art of Illusion modelling tutorial - the hourglass
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Imagine it
This is where the tutorial ends, but Art of Illusion is capable
of much more than shown here. From other tutorials and the manual
you maylearn about these. Most of the cool features are intuitive
enough though, and you can simply try them all and see their
effect.
Using the basics from this tutorial you can now start modelling
the worlds of your imagination. Gradually, as you learn to master
all of theprogram's features, you'll get better and better... and
more addicted.
Good luck.
artofillusion.orgArt of Illusion modelling tutorial - the
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