The objective is to learn to use Maya's lights, surfaces, textures, more advanced modeling techniques, and rendering capabilities. As usual, a complete explanation of how to use Maya is not possible here. Further instructions will be given in class, and the readers and tutors will provide it outside of class. Some online help is also available.
Using advanced rendering and complex objects, shaders, and lights can really tax the computing power of these moderate-speed machines. Not only will rendering take longer, but because the rendering is using the processor, everything else will take longer also. It is wise to use crude shading and rendering to design the scene, and to add advanced options gradually. Also, remember to save multiple copies of your work as you progress, so that you never inadvertently damage your scene or file and have nothing to go back to. Make sure you are not animating! Set the renderer to only create one image.
This is a fairly complex assignment so it would be wise to do it early, before machines and tutors become busy.
For full credit on this assignment, fulfill all these conditions. The requirements must be clearly visible in both of the .jpg images that you submit.
Light are another fundamental object in Maya. Without light, there will be total darkness and you won't be able to see anything. Initially, Maya provides one default light that is above the ground plane. Under Lighting, this is the choice Use Default Lighting.
You can add a new light from the Create menu. Pick the Lights submenu, and then select the type of light you would like to add (the types are described below). An icon representing the light will appear at the origin of the scene. You can change the name of the light in the Channels window (on the right of the screen); try to pick something descriptive that will let you easily identify it later on.
When you add new lights, the Lighting automatically changes to a scenario where your created lights (Use All Lights) are used in the scene instead of the default. Or, you can show the effect of only the selected lights. (Aside: if you remove your lights and still ask to see All Lights, nothing will appear in the scene windows, but a rendering will automatically give you a default light. If you would rather see a black rendering, you can turn this off in the Render Globals window.
| Picking Lights and object properties | Light Attributes panel |
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All the lights can be given a color, and the default is white. Click on the Color choice in the light's Attribute Editor to reset the color. The slider next to the Color choice seems to have the save effect as the Intensity slider below it. Probably the effect of the two is accumulated.
As stated in the shading notes, computing the realistic amount of continuously reflected light between all surfaces is very difficult and computationally expensive. To simulate the effect, Maya uses a very common practice: ambient light. An ambient light is essentially a "background noise" light, a constant amount of light shown on all surfaces regardless of their location and orientation at all times. You can adjust the color and intensity of the ambient light. The default is set at "white" and ".50" respectively, which is adequate for most scenes. Ambient light is usually set to a low intensity if it used in a scene.
Ambient lights in Maya are actually not traditional ambient lights as usually defined in computer graphics. Traditionally, there is at most one ambient light and its location has no effect; it shines everywhere. In Maya, the ambient light is a combination of an ambient light and a point light (see below), so moving it around has an effect.
A directional light is best exemplified by sun light. It comes from an infinite distance away, and the light rays are always parallel to each other. The directional light has three properties that really matters - direction, color, and intensity. The direction can be controlled by physically rotating the light object using the rotation transformation tool, or by using the specialized manipulator tool for this type of object using Modify->TransformationTools->ShowManipulatorTool. Color and intensity can be changed in the channels/object window, or the attribute editor.
A typical example of a point light is the candle, which sits at one position and emits light into space all around it. The position of the point light matters, just like the position of a candle determines what area it will light up. There is also an "Decay Rate" option, which determines how far the light will shine before its intensity diminishes, also known as attenuation. There are four types of Decay Rate which affect how fast the light changes from full intensity down to no intensity as it gets further from its source.
In the examples below, the green ball represents the point light above the
white ground plane. All other lights (including Ambient light, which we talked
about above) have been turned off.
| No Decay | Linear |
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Quadratic |
Cubic |
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A spot light is a "cone" of light. Both its position and direction affects its results. Again, these two parameters have to be changed within the layout view. A spot light also has three more unique parameters, "Cone Angle" and "Penumbra Angle" and "Drop-off". "Cone Angle" defines the angle of the cone. "Drop-off" defines how much "escaped" light goes to the areas around the defined cone. So a spot light with "Drop-off" of zero will create a rather sharp spot on a flat surface, whereas a larger "Drop-off" value will make the area surrounding the spot soften. "Penumbra Angle" controls a drop off outward from (+) or inward from (-) the edge of the spot. You probably need to render the scene to see the effect of a penumbra.
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Spotlight Options |
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| No Dropoff | Some Dropoff => Soft Edge |
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Area light can be thought of as a rectangular array of point lights; it sends out light in all directions. Very similar to directional light, the orientation and position affect its results greatly. Again, we leave it up to you to explore its uses. Area lights can be expensive to use (in time).
Volume lights cover a volume of space. You guys get to figure this one out. This can also be time-consuming.
Lighting is a very important part of graphics. There are lots of lighting effects that we did not touch on, such as caustics, refraction, etc. Maya has a very powerful lighting system so it is worth your while to spend some time playing with different lighting effects by changing the attributes of the lights you create.
In the real world shadows are created when an object blocks light from passing through. By default, 3D scenes do not create shadows. An object will not cast a shadow unless you set the scene up to cast shadows. Realistic shadows are expensive, in terms of rendering and computations, but there are ways to speed the process up. The most accurate way to create shadows is through a process called ray tracing. Ray tracing involves shooting rays from a light source along its orientation. When the light ray intersects and object, it will stop (if the object is opaque). Everything blocked by the object will not be illuminated by that light, resulting in a shadow. To achieve this effect in Maya you can set the Shadows parameters in a light's attribute.
For Ray traced shadows check "Use Ray Trace Shadows" under Light Attributes: Shadow>Raytrace Shadow attributes. The Shadow Rays and Ray Depth attributes control how accurate the shadows are. You also need to change the the Render Globals attributes to use raytracing:
Render Globals>Raytracing Quality>Use Raytracing
A quick and dirty way to get shadows is to use depth mapped shadows. This is less expensive then ray tracing. Under the light attributes for a light select:
Shadows>Depth Map Shadow Attributes>Use Depth Map Shadows
As discussed in the class, notes, and text, the effect of lights depends on the surfaces that they strike and reflect from. Various parameters to change this are found in the "Material Attributes" window. You have already learned how to change the basic color of the surface by assigning a material to the object.
Different material types will have different parameters. Lambert materials have a more matte appearance, while Blinn has a more shiny look. Blinn materials let you affect how shiny the material appears by allowing you to change with the specular highlights. There are more material types as well for you to experiment with. Below are properties common to all materials. Material parameters are simplifications of reality, and you aren't constrained to mimic reality when you use them.
In Blinn materials, the eccentricity controls how big the specular highlight is. Eccentricity is the amount of incoming light that is reflected out in the specular direction. This affects the brightness of highlights. The greater the value, the more polished the object, hence the smaller the highlight spot becomes. Specular Rolloff is like attenuation in lights, controlling how the specular blends into the rest of the material.
Maya provides a Hypershade window/panel that provides a graphical user-interface (GUI) to the materials and material assignment. You can move around in the hypershade window the same as moving the camera in Maya, except to zoom in click and drag a selection marquee down and too the left.
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"Transparency", as the name implies, controls how transparent the object is. The more transparent the object, the more light is allowed to pass through it. "Refractive Index" is the same concept as in physics; it controls the angle at which light enters and leaves an object. The default "Refractive Index" is 1.0, which is that of the air. To make light bend as it goes through an object, such as glass, this value has to be changed.
"Refraction" simulates how light bends when it passes through a semitransparent or transparent object. To change the refraction of an object, adjust the refraction in the material attributes for the object's material. Refraction can only be rendered using raytracing. Different materials have different indices of refraction, with the higher the index, the more "bend" the light undergoes. Most indices are around 1.0 - 1.5. In the Render Globals you can set the depth of refraction (i.e. a sphere would have 2 depths, one for the front surface, one for the rear surface).
"Translucency" is similar to "Transparency" in that color and light effects are shown through. The difference is that objects on the other side of a translucent object are not visible. You can use translucency to make effects such as the silhouette of an object on a stage curtain, or to see the bones in your character's hands if the hands are held up to a light source.
You can think of texture mapping as wrapping a very stretchy wall paper on the surface. Normally, whatever surface color you designated for the object will be thus overridden by the texture. Textures work on the face level of the object. A texture has U,V coordinates that range from 0-1. When you apply a texture to an object you are specifying which vertices of the object have which U,V coordinates. Changing the U,V coordinates changes how the image is pasted on to the object's faces.
Nearly every material attribute can have a texture assigned to it. While your
object may look like wood (wood texture), it can reflect like water. In this
assignment, we will only touch the basics of texture mapping. To texture map
a surface, click on the 
button next to "Color". This will bring up the "Create Render
Node" window for the material. You can have 2D or 3D textures, the most
common being 2D. To pick an image you have created as a texture, select the
file icon. Or you could use the other existing texture types for the texture
map.
Normally, you want to map the texture, which is often a rectangular bitmap (really a digital image), to the object with the appropriate type. Once a texture is applied to an object, you can change how the texture "fits" around the object as well as what part of the texture is displayed on the surface. For example, if you want to make the Earth, it's most logical to choose the "Spherical Mapping" type rather than "Planar Mapping", since you want to wrap the image around the a sphere, not a cube. If you want to show a wall painting on a flat surface, you'd want to use the "Planar Mapping" type, not "Spherical Mapping" or any other. You can access the texture projection as well as other features of textures for an object from the Edit Polygons>Texture menu.
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There is a special window in Maya used for modifying texture coordinates
called the "UV Texture Editor" under the Window menu. The texture
editor localizes a lot of the features you can use for placement of textures.
There is not enough space for a full tutorial on the texture editor, and
it is not required for this assignment. It is a useful tool for more advanced
texturing. A fairly simple tutorial is available at: http://uj.furrycat.net/modelling/uv.html.
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You can have multiple layers of textures, such as a bump map as well as a normal texture. If you need more then one texture of the same type you can apply a multi-texture.
You might enjoy mapping the image of yourself that you used in the first assignment onto a 3D object.
This is just to illustrate some techniques. You should make something else for your object. You must make the object "from scratch" on your own, without importing pre-made objects other than the standard primitives. To start we will reset the scene using File > New Scene.
We are going to use the create curve tool to design a curve. Later on, we will rotate this curve to design a symmetrical object. This curve is simply the cross-section of a symmetrical object. To sketch this curve, choose the "CV Curve" or "EP Curve" tool from "Create" and then, in the "Side (XY)" view, sketch the outline of one side of a table leg on the right hand side of the Y axis - use your imagination to come up with a unique leg style that you like. Remember, you will need to press enter to finish the line you just created.
CV Curves are approximating curves that come close to the control points, but give you a better control over the curvature of the shape. EP Curve are interpolating curves that pass through edit points on the curve. To create a curve, choose one of the curve types in the create menu, and then click where you want the control points to be. Press enter when you are done creating points.
If you need to adjust the positioning of any of the points, select Control Vertex by right clicking on the curve. This lets you change the position of the curve control points, altering the shape of the curve, by selecting a control point and moving it with the move transform tool. Select the point (or points) you want to move and then use the "Move" tool to drag them around. You should limit your editing to the "Side" view so that your line stays planar (we'll make the shape 3D in the next step). Remember that if you need to undo your actions at any time, you can use undo (ctrl-z) and redo.
The Revolve tool is used to make objects that are symmetrical around one axis. Activate the Revolve tool by selecting Surfaces>Revolve. Another word for revolve is lathe. You can edit the results of the revolve by changing the attributes in the channels window by clicking the revolveX under the Inputs label.
In the numeric interface, you will see the following values: Start Sweep 0, End Sweep 360, Sections 8, Axis, and Pivot. Make sure that the Y axis is 1. In the perspective preview, you should see a four sided table leg appear where there was only a line or a polygon before. You can experiment by choosing different numeric values (such as the number of sides to design a smoother leg). You can change the 3D shape by changing the original curve you used for revolving. Select the curve, and then the control points, and move them around. Play with this and see how it affects the shape.
Extrude is similar to revolve but instead of sweeping the curve around a curve, it sweeps a curve along another curve in space. Create a curve as before. Create a second curve that comes out from the first curve in another direction. You can do this by creating the curve is a different orthogonal window. The first curve is the profile curve and the second curve is the path curve. Select them both (holding down the shift or control key), the profile first. Then use Surfaces->Extrude.
Lofting creates a surface between two or more curves. Create a few curves that are in different planes. An easy way to do this is a create one curve and then duplicate it and move the duplicates away from each other. Select them in the appropriate order. Choose Surfaces->Loft to see a surface between them.
Once you have a surface, you can modify it locally, that is by deformations that change part of the surface but not all of it. A simple way to do this is to use the right button over the active object to select Control Vertex for NURBS objects or Vertex for polygonal objects. (You can go back to selecting whole objects by using the right button over the object and choosing Select.) After switching to the new mode, you can select some of the vertices and control points and deform them as usual using translate, rotate, and scale. For NURBS objects, there is also a specific EditNURBS->SculptSurfacesTool. To use this, change the mode to selecting Surface Patches using the right mouse button over the object. Then the left mouse button will push, pull, smooth, or erase the surface in the area of the mouse. Select the details option of the SculptSurfaceTool to choose options. If you want to "sculpt" for the assignment, remember that you don't have to use this tool, but can just moves vertices and control points as described above. option.
Objects that you design in Maya can be easily bent, twisted, tapered
and sheared. Choose the "Animation" menu subset. Then under Deform
> Create Nonlinear > Bend. You can click and drag to bend your
object around the axes in the view you dragged in. Similarly, you can twist,
flare and squash the objects as well. Once the object is deformed, you can either
numerically adjust the values in the channels window or you can click on the
manipulator tool 
and then click the central line in the object. If you drag the center point,
it affects the bend, or deformation. The end points affect the area affected
by the deformation.
Duplicating refers to the process of cloning the same object. The approach in the duplication tool is to first select one or more objects, click on the "Duplicate" tool under the "Edit" menu, making copies at the same location as the selected object.
Position the legs of the table so that they could support a table top.
Create a table top and position it over the table legs by creating a cube and scaling it accordingly, or changing the values under the Inputs in the channel window. Give enough thickness to the table top so that the legs you created earlier penetrate into the table top. You will need to do this in order to work with the Boolean operations later.
Voila, you now have a nice table.
To create a 3D text, as opposed to 2D text, you must first create 2D text as
in the previous assignment. Then, select the faces of the text. Then use Edit
Polygons > Extrude. You can affect the extrusion by using the manipulator
tool.
Most of the procedures on how to render a scene were covered in the first Maya. Note, however, that because some of your objects will be reflective and/or transparent, it is very important that when you render you set the raytracing options in the render globals. Otherwise, even if your object is 100% reflective, it may not reflect the object right next to it. Notice that by turning on these options, depending on the complexity of your scene, rendering time can also increase dramatically.
Questions? E-mail Narayan Brooks
or Jane Wilhelms.
Or e-mail the class news group.
