art of illusion modelling tutorial - the hourglass

Art of Illusion modelling tutorial - the hourglass

http://www.artofillusion.org/docs/hourglasstut/[5/12/2015 5:17:57 PM]

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



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).



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:



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.



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.



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:



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.



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:



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:



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



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.



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:



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 hourglass

art of illusion modelling tutorial - the hourglass

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