October 23, 2007 Workshop 9 Notes

LIGHTING AND MATERIALS

This workshop is developed the Robinson text, and contains examples that are reinforced by background concepts in Chapters Chapter 14 + Chapter 15 (part), pages 349 402 

1. Shader types in Maya are based upon standard rendering algorithms:  

• Lambert – flat – cosine shading (Lambert’s law)
• Phong – typical phong (spectral highlight)
• Phong E – spectral highlight in white
• Blinn – metallic objects
• Anistropic – good for material with grooves
• Layered Shader – more than one material
• Ramp Shader – ramp color (eye ball)
• Shadows …. Map of shodow lines from viewpoint of light sources (geo calculation)

These types of shaders are acessible through the hypershade dialog box or Window/Rendering Editors/Hypershade

2. Lighting types & 3 pts lighting  - Chapter 14

Lighting types commonly used are 1) Ambient, 2) Distant/Directional, 3) Point and 4) Spot Light which appear from left to right in the Rendering Shelf tab in Maya. Ambient light provides general background illumination. A Distant/Directional light provides parellel light rays from a specific angular orientation, and may be used to mimic such distant lights as sunlight or moonlight. A point light is an omni-directional light that sends light out in all directions from a single location. A directional light sends light in a specific direction at a specific angle from a source location to a target location. 

Key and Fill Lighting: A typical three point lighting setup has a Spot light (also known as a Key light) to the upper right of model at full intensity to provide high contast shadows, a Point light (also known as a fill light) to the upper left of the model at lower insensity filling in middle grey values, and a back spot light (also known as a back key light) at lower intensity than the front spot light and that provides some three-dimensional depth to the rendering.   

Key light set at full intenstity and positioned using the show manipulator tool (selected tool on left-hand side of Application window).

3. Materials Some Definition of Textures and Methods

Materials reference attribute nodes that determine look of an object. This includes

Texture – an material  that is mapped to object
      Types:  procedural (based on an algorithm) and
                    image (based on a photograph).

Bump Map – image read for its grey scale value that makes a material have the appearance of a surface relief

4. Menu items in Hypershade window (Left to Right)

Toggle bar – hide or show Create bar leaving more or less work area
Show top and bottom tabs - shows materias/textures as well as work area.
Show bottom tab - shows work area
Show top tab - shows materials/textures
Show previous graph (in work area)
Show next graph (in work area)
Clear Graph bar – clears out any nodes in work area
Rearrange graph bar – cleans up work area
Graph materials on select objects – finds material assigned to object
Show input connections
Show input and output connections
Show output connections

5. Basic material properties:

Color – RGB or HSV sleection model color
Transparency – degree to which material is transparent
Ambient Color – brightness or darkness of whole material
Incandescence – create appearance of giving light
Bump mapping – makes a surface appear bumpy

6. Example of use of simple material definition and assignment

Change color of an object

1. from Windows menu select Rendering Editors -> Hypershade
2. Select create materials
3. Click Lambert (cosine shaded object)
4. Double click the new material to invoke attribute editor 
5. Select field next to color on right-hand side of screen.
6. Choose color from rgb or hsv model/accept
   
   
   
   
   
7. Drag material with middle button onto surface from icon in work are to object. Or select surface and select material with right mouse button, select “Assign Material to Selection”

6. Texture mapping nurbs surface

Prepare brick.jpg file or somephoto.jpg file. Make a material from a lamber shader. In the color selection area on the right-hand side of  the the screen, select the checkered symbol and follow the dialog box to load the brick.jpg file.

1. Nurbs surfaces U horizontal – V vertical map from lower left corner to upper right
2. Can map TIF, JPG and Maya’s IFF
3. Create Lambert material
4. In Hypershade panel double click on icon.
5. Add brick file to material
6. Select object, right click on lambert material and assign to object
7. Double click on pace2dTexture node
8. See red square on object: middle mouse button - drag center to move, drag corners to rotate,
9. Repeat UV … to repeat pattern (do 4 in each of U and V)

7. Ramp texture (eyeball)

1. Create Phone E shader
2. Double click on the icon (gets attributes window), and then click checkerboard icon on the color.
3. Select ramp shader.
4. Change top shader to black by lowering color solider to left.
5. Move middle shader (default color is green) closer to top
6. Click on ramp 1/5th way to bottom, place new position indicator just below 2nd one (above).
7. Click and drag bottom indicator just below new one (3rd one).
8. Click on color swatch for above indicator and select white.
9. Change shader type to U Ramp and assign to sphere

8. Layered Shader

1. Create two blinn shaders red and blue.
2. In blue shade, double clock on icon, and then on transparency color select fractal.
3. Create layered shader
4. Double click on layered shader material.
5. Drag blue and redmaterials from the Hypershade into the red square under Layered Shader Attributes. (note blue shader comes before red shader)
6. Click X under original green shader to remove it.
7. On blue blinn shader, use fractal to define transparency
8. Apply shade a square
9. In Render view, click on the Redo Previous Render Icon. Red can be seen through the blue due to fractal transparency.

9. Bump Map

1. Create NURBS plane.
2. Hypershade create Lambert and assign to plane via MMB.
3. Double-click on Lambert sphere.
4. Click map button next to bump mapping and select bulge.
5. From Create Menu/Select Lights/Directional light.
6. Use Show Manipulator Tool to rotate light onto plane.
7. Select render icon (upper right hand side of screen) to see bump map..
8. To change bump depth/chose graph materials on selected objects icon in hypershade panel and select lambert object.
9. Select bump2d node, increase bump depth , & render (render icon)

10. Projection Map

1. Create NURBS plane.
2. Create a lambert material in Hypershade and apply to plane.
3. Double-click on the lambert material in Hypershade
4. In attribute editor, click on map next to color slider.
5. Click on radio button to projector.
6. Click the file button (select a file).
7. Click file1 tab at top of attribute editor.
8. Click on folder icon next to Image Name
9. Open your own image.
10. Goto perspective view and select key #6 to render.
11. Select the place3d texture utility in the perspective view.
12. Rotate plane -90 so that image projects onto NURBS plane.
13. With the place 3d texture tool selected press ctrl/ctrl – a to open attribute editor.
14. Click the “fit to box” button.
15. Experiment with scale and move options.

[If surface appears to be moving through texture, then in Rendering mode, select the surface, and then from the Texturing menu select “Create Texture Reference Object”]

11. To Improve Quality of Rendering

1. Select object.
2. In hypershade panel, choose Graph Materials on Selected Objects Icon.
3. Double-click on the material in Hypershade.
4. In Attribute editor, under Hardware Texturing, click arrow to expand options.
5. Change “Texture Quality” setting to High. {only do for temporary viewing, slows Maya down]

12. 3D Paint Tool

1. Create Lambert material and assign it to a new NURBS sphere.
2. Select the sphere.
3. From Texturing Menu, select box next to 3D Paint Tool.
4. Scroll down until you see File Textures.
5. Click the Assign Textures button, determine resolution, and click Assign Textures {note project setup must include texture area
6. In perspective view, hold “b” key and move mouse left & right to size brush.
7. Click and drag on surface to paint.
8. Select swatch next to floor color and choose yellow at top of Color Choose.
9. Click “Flood Paint”
10. Change paint color and paint smiley face on surface.
11. Click on the change brush button, scroll down Visor and select hair folder.
12. Choose hair type and paint on to sphere.
13. Clear surface with flood button.
14. Select brush adjacent to Artisan to return to normal bursh.
15. Decrease capacity of brush to see color beneath
16. Can edit image in Photoshop directly from directory.
17. [techniques can also be used for Attributes and Transparency, pull-down menu under file textures.

13. Camera Attributes:
 1,  View window/view menu.
 2.  Depth of Field Attribute (tied to fstop).
3. Select view depth (depth of field is distance before & after).

14. Depth of field is the region of sharp focus in a photograph. Depth of field is determined by the camera's aperture setting. At wide aperture settings (for example, at fStop f/2), the depth of field is shallow, and more of the foreground and background (that brackets the area in sharp focus) is out of focus. At narrow aperture settings (for example, at fStop f/22), the depth of field is deep, and more of the foreground and background is in focus.
Motion Blur/Render Globals Option
1. Simluates blurred motion on object.

View/Import Image (sets view background image)

Fit to Resolution Gate – Rendering resolution
Fit to Film Gate – fits to Camera resolution (aspect ratio)

IPR Rendering (interactive rendering not avail in raytracing – see changes immediately)

1. Select NURBS plane with bump map.
2. IPR rendering, draw box about plane.
3. Update bump depth (to 2)
4. See Changes immediately