Advanced Maya Texturing and Lighting- P9 pdf

the outcolor of the fractal node is connected to the transparency of a blinn material node named propellercolor.. For example, in Figure 7.16 the transform node of a single-node camera,

output color

Figure 7.14 The colors of two abstract shapes are controlled by a Distance Between utility This scene is included on the CD as

Creating Simulated Propeller Spin

A spinning plane propeller is basically a blurred disc Although the prop is visible

with the correct point-of-view or proper frame rate, its shape is generally indistinct

You can emulate a spinning propeller in maya by having a propeller disc drive its

own transparency For example, in Figure 7.15 a nurBS disc is animated rotating

from 0 to 10,000 degrees in Z over a period of 90 frames

rotateZ input1X

outputX input1X

outputX

offsetU

outC olor

placementMatrix

outC olor color

Figure 7.15 A NURBS disc serves as a spinning propeller The opacity flicker is driven by its own geometry The yellow arrow

indicates the point at which Maya inserts a unitConversion node A simplified version of this scene is included on the CD as

the rotateZ of the disc’s transform node is connected to the input1X of a plydivide node named multiplydivide1 the outputX of multiplydivide1 is connected

multi-to the input1X of a second multiplydivide node named multiplydivide2 the input2X

of multiplydivide1 is set to 0.01 the input2X of multiplydivide2 is set to 0.005

this sequence converts a potentially large rotation value into an extremely small one

the outputX of multiplydivide2 is connected to the offsetu of the place2dtexture node belonging to a fractal texture node thus, the rotation of the disc automatically pushes the fractal texture node in the u direction the repeat uV of the place2dtex-ture node is set to 0.001, 0.001, which reveals only a small section of the fractal the custom settings for the fractal texture node are as follows:

ratio: 0.5Frequency ratio: 10Bias: –0.3

Filter: 5

these adjustments create a softer version of the fractal pattern the outcolor

of the fractal node is connected to the transparency of a blinn material node named

propellercolor As the disc rotates, the fractal moves left, revealing darker and lighter

sections hence, the propeller disc flickers during the animation the color of the disc

is derived from a circular ramp texture with brown and yellow handles the ramp is

projected onto the disc for a more exact lineup of colors while this technique might

not work for close-ups, it can be used successfully for wider shots and flybys it also

serves as an extremely efficient method of rendering since no motion blur is involved

Reproducing the Hitchcock Zoom-Dolly

Alfred hitchcock introduced a famous zoom-dolly camera move in the film Vertigo

(1958) Steven Spielberg later popularized the same motion in Jaws (1978) if a camera

zooms out while simultaneously dollying forward, the background distorts over time

this is due to the optical nature of the camera lens telephoto lenses (for example,

300 mm) flatten a scene, but wide lenses (for example, 24 mm) give a scene more

depth it’s possible to change the focal length of a zoom lens with a twist of the hand

(for example, 200 mm to 50 mm)

You can automate the hitchcock zoom-dolly with custom connections For example, in Figure 7.16 the transform node of a single-node camera, named hitch-

cam, is parented to a group node named hitchcamgroup to view the custom

shad-ing network, open hitchcock.ma and follow these steps:

1. open the hypershade window and switch to the utilities tab

2. mmB-drag the multiplydivide node into the work area

3. with the multiplydivide node selected, click the input And output connections

button

hitchcamgroup is animated along the Z axis hitchcamgroup’s translateZ attribute is connected to the input1X of the multiplydivide node the outputX of

the multiplydivide node is connected to the focallength of the camera’s shape node,

named hitchcamShape the multiplydivide node’s operation is set to multiply, and

its input2X is set to 10 when hitchcamgroup is at its start position of 0, 1, 10, the

focallength of hitchcamShape is 100 when hitchcamgroup is at its end position of

0, 1, 1, the focallength of hitchcamShape is 10 Scrubbing the timeline will quickly

show the high degree of distortion that happens to the background and foreground

objects An animation curve node—seen at the top of the network—appears because

an attribute is keyframed even though hitchcamgroup is the parent of hitchcam,

there is no visible connection in the hypershade window

on top of itself is the quickest way to do this Choosing Other from the Connect Input Of menu opens the Connection Editor and reveals that the node is listed in both the Output and the Input column That said, an attribute cannot be connected to itself (for example, focalLength

to focalLength) Nevertheless, two different attributes can be connected (for example,

focal-Length to shutterAngle)

focalLength

input1X

translate Z

Figure 7.16 A Hitchcock zoom-dolly is created by connecting a camera’s translation to its focal length This

scene is included on the CD as hitchcock.ma A QuickTime movie is included as hitchcock.mov

Tapping into Construction History Nodes

You can put construction history nodes to work in the hypershade window in ure 7.17, an asteroid model automatically receives more surface detail as it approaches the camera along the X axis

Fig-to view the entire cusFig-tom network, open history.ma and follow these steps:

1. open the hypershade window and switch to the utilities tab

2. mmB-drag the clamp node into the work area

3. with the clamp node selected, click the input And output connections button

A portion of the network becomes visible

4. Select all the visible nodes and click the input And output connections button

a second time

inputP olymesh

transla teX

input1X

outputX

Figure 7.17 A polygon asteroid receives more detail as it approaches the camera Iterations of a Smooth tool are driven by custom

connections This scene is included on the CD as history.ma A QuickTime movie is included as history.mov

For the network to function, the animated translateX attribute of the pSphere polygon transform node is connected to the input1X of a multiplydivide node the

multiplydivide node’s operation is set to divide and its input2X attribute is set to

15 this division increases the amount of distance the asteroid must travel before

the detail is increased the outputX of the multiplydivide node is connected to the

inputr of a clamp node the outputr of the clamp node is connected to the divisions

attribute of a polySmoothFace node the polySmoothFace node is a product of

choos-ing mesh > Smooth whenever the Smooth tool is applied, it creates two new nodes:

polySmoothFace and polySurfaceShape the divisions attribute of polySmoothFace

controls the number of iterations the Smooth tool undertakes the clamp node’s

maxr attribute is set to 3 so that the iterations stay between 0 and 3 the surface’s

pre-Smooth state is retained by polySurfaceShape Both polySmoothFace and

polySur-faceShape nodes, like all construction history nodes, will exist until history has been

deleted on the polygon surface (edit > delete By type > history)

Redirecting the Initial Shading Group Node

By default, maya assigns all new geometry to the initial Shading group and the bert material connected to it (named lambert1) You can replace the lambert with a Blinn or any other material by deleting the connection between the outcolor of the default lambert material node and the surfaceShader attribute of the initialShading-group node You can locate the initialShadinggroup node by clicking the input And output connections button while lambert1 is selected You can then connect the outcolor of a new material to surfaceShader of the initialShadinggroup From that point forward, all new surfaces are automatically assigned to the new material (see Figure 7.18) the outcolor of the default lambert material node is also connected to the surfaceShader of the initialparticleSe node A different material can be connected

lam-to this as well the initialparticleSe node determines the default material qualities of software-rendered Blobby Surface, cloud, and tube particles

outC olor surfac eShader outC olor surfaceShader

New default Blinn

Old default Lambert

Figure 7.18 The default Lambert material is replaced with a Blinn This scene is included on the

CD as initial_shading.ma

group node with a name along the lines of blinn1SG These material-specific shading group nodes can

be deleted and replaced if necessary For additional information on shading groups, see Chapter 4

Connecting Multiple Materials in One Network

A custom shading network is not limited to a single material in some situations, necting one material to a second material can force the renderer to apply an additional layer of evaluation to the assigned surface As a simple demonstration of this, the out-color of a phong material node is connected to the color of a lambert material node

(see Figure 7.19) Although the lambert node does not have the ability to produce a

specular highlight, it picks up the look of a specular highlight from the phong.

outColor

color

Figure 7.19 A Lambert material inherits the qualities of a Phong.

to achieve this, the renderer evaluates the assigned surface as if a phong rial was assigned to it the renderer takes the color information from this evaluation

mate-and applies it to the color of the lambert material this evaluation occurs at each

pixel and the color is assigned at each pixel if a pixel is white with the phong shading

model, then the lambert color is white hence, a false specular highlight is produced

Any attribute of the phong material node that is mapped will carry through For

example, if a texture is mapped to the Bump mapping attribute of the phong node, the

bump will appear automatically on the lambert node

Note: For a demonstration of a complex, custom skin shader that uses the majority of techniques

in this chapter (including multiple materials), see section 7.2 of the Additional_Techniques.pdf

file on the CD

Using the Studio Clear Coat Utility

Studio clear coat is a plug-in utility that’s in its own category its sole function is to

create reflections with uneven intensity As opposed to the car paint shading network

detailed in Figure 7.2, this utility functions as a single node

For example, in Figure 7.20 the outValue of a studioclearcoat node is nected to the reflectivity of a blinn material node (named car_paint) the same light-

con-ing and environment that was used in Figure 7.2 is applied here the studioclearcoat

node has an index value of 1.7, a Scale value of 1.55, and a Bias value of –0.1 the

resulting render is almost identical to Figure 7.2 the main difference is the rapidity

with which the Studio clear coat utility transitions between the hood reflection and

fender reflection Although this is not necessarily better or worse, the Studio clear

coat utility is extremely easy to apply unfortunately, it will not work with the mental

ray renderer the custom paint network used in Figure 7.2, on the other hand, offers

more flexibility with the addition of the Value gradient and will work with maya

soft-ware or mental ray renderers

Figure 7.20 The reflective falloff of car paint is controlled by a Studio Clear Coat utility A simplified version

of the scene is included on the CD as clearcoat.ma.the Studio clear coat utility’s attributes follow:

Index represents the refractive index of the surface A refractive index is a constant

that relates the speed of light through a vacuum to the speed of light though a material (such as car paint) the constant follows:

speed of light through a vacuum

÷ speed of light through a material

water has a refractive index of 1.33, which equates to 1/0.75 the speed of light through water is only 0.75 times as fast as the speed of light through a vacuum the refractive index of air is extremely close to 1 and is considered 1 when working in 3d

As light passes between two materials that possess different refractive indices, the angle

of refraction does not match the angle of incidence (the angle between the incoming light ray and the material boundary normal, which is perpendicular to the boundary surface) if the light passes from a material with a low refractive index to a high refrac-tive index, the angle of refraction is rotated toward the material boundary normal hence, objects appear bent (for example, when a pole is dipped into water) the clear-coat paint systems on modern cars produce a refractive index somewhere between 1.4 and 1.8 the amount of perceived distortion is minimized by the extreme thinness of the transparent clear-coat layer (an average of 50 to 100 microns)

Scale Serves as a multiplier for the final result higher values will make the reflection

more intense

Bias offsets the intensity of the reflection lower values decrease the intensity of the

reflection and increase the contrast within the reflection higher values increase the intensity and lower the contrast the default value is –0.1

Note: If the Studio Clear Coat utility is not visible in the General Utilities section of the Hypershade

window, choose Window > Settings/Preferences > Plug-In Manager and click the Loaded check box for

between angles of incidence and angles of refraction The law is named after Willebrord Snell (1580–1626), who developed a mathematical model based on earlier investigations by Claudius Ptolemy (ca 100–170) and others For more information on Snell’s Law, see Chapter 12

Chapter Tutorial: Building a Custom Cartoon Shading Network

in this tutorial, you will create a custom cartoon shading network that combines solid

colors with a simulated halftone print (see Figure 7.21) Sampler info, Surface

lumi-nance, condition, and multiply divide utilities will be used

Figure 7.21 A custom cartoon shading network applied to primitives A QuickTime movie is included

on the CD as cartoon.mov

1. create a new maya scene open the hypershade window

2. mmB-drag a Surface Shader material into the work area and rename it

Cartoon mmB-drag a condition utility (found in the general utilities section

of the create maya nodes menu) into the work area place it to the left of the cartoon node use Figure 7.22 as a reference

ConditionA

place2dTexture ConditionB

projection

RampA

Figure 7.22 The shading network of the custom Cartoon material

3. connect the outcolor of the condition node to the outcolor of the cartoon node You will have to open the connection editor to do this

4 Select the condition node and rename it ConditionA open its Attribute editor

tab click the color if False map button and choose a ramp texture from the create render node window A place2dtexture node will automatically appear

with the new ramp node rename the ramp node RampA.

5. Select rampA and open its Attribute editor tab create four color handles that

go from black to green to white (see Figure 7.23) change rampA’s tion attribute to none

interpola-6. mmB-drag a Surface luminance utility (found in the color utilities section

of the create maya nodes menu) into the work area place it to the left of the

other nodes connect the outValue of the surfaceluminance node to the

first-term of conditionA

7. connect the outValue of the surfaceluminance node to the vcoord of rampA

You will have to use the connection editor this connection forces the render

to select different pixels in the V direction of the ramp based on the amount of

light any given point on the assigned surface receives if a surface point is dark,

it gets its color from the bottom of the ramp if a surface point receives a erate amount of light, it gets its color from the center of the ramp

mod-8. mmB-drag a second condition utility into the work area place it to the left

of conditionA rename the new condition node ConditonB connect the

out-color of conditionB to out-coloriftrue of conditionA

Figure 7.23 (Left) RampB (Right) RampA

9. mmB-drag a Sampler info utility (found in the general utilities section of

the create maya nodes menu) into the work area place it to the left of ditionB connect the facingratio of the samplerinfo node to the firstterm of conditionB

con-10. Select conditionB and open its Attribute editor tab Set the color if False

attri-bute to 0, 0, 0 click the color if true map button, select As projection in the 2d textures section of the create render node window, and click the ramp texture button Selecting As projection creates the ramp texture with a projec-tion node and a place3dtexture node (see Figure 7.22) rename the new ramp

node RampB.

11 create a new one-node camera by choosing create > cameras > camera from

the main maya menu create several primitives and place them in the view of the camera Assign all the primitives to the cartoon material Feel free to change the camera’s Background color attribute to white or add a white ground plane

12. Select the projection node and open its Attribute editor tab change the proj

type attribute to perspective mmB-drag the new camera node, named camera, from the cameras tab area to the work area and drop it on top of the projection node choose other from the connect input of drop-down menu the con-nection editor window opens connect the message of the camera node to the linkedcamera of the projection node the message attribute is normally hid-den when you choose left display > Show hidden in the connection editor, the message attribute becomes visible at the top of the list when the camera

node is connected to the projection node, the projection node will know to

proj-ect from the view of the new camera and not the default persp camera

Figure 7.24 Selected camera frustum

14. Select rampB and open its Attribute editor tab place two color handles in the color field A black handle should be at the bottom A dark purple handle should be at the center (Figure 7.23) Set type to circular ramp and interpola-tion to none rampB will produce a halftone print pattern Select the place2d-texture node of rampB open its Attribute editor tab and change the repeat

uV value to 65, 40 choose larger numbers to create smaller halftone circles

15. Select conditionB and open its Attribute editor tab Set the Second term bute to 0.3 and the operation to greater than conditionB works as an if statement if the facingratio of the samplerinfo node is greater than 0.3, con-ditionB will output the halftone pattern of rampB as the color if the facingra-tio is 0.3 or less, pure black will be output as the color; ultimately, this creates a black “ink line” around the edge of the objects

attri-16. Select conditionA and open its Attribute editor tab Set the Second term bute to 0.5 and the operation to less than conditionA serves as a second if statement if the outValue of the surfaceluminance node is less than 0.5, the

color output by conditionB is selected (black or halftone dots) if the outValue

of the surfaceluminance node is equal to or greater than 0.5, the color output

by rampA (various shades of green) is selected the surfaceluminance node also controls the vcoord of rampA, so that the selection of different shades of green is based on the amount of light the surface receives

17. the custom cartoon material is complete! render out a test it should look

simi-lar to Figure 7.21 if you get stuck, a finished version of the material is saved as

8

Math utilities refine outputs and emulate complex mathematics Switch utilities let you create numerous texture variations with

a single material With Array Mapper and Particle Sampler utilities, you can control a particle’s material and movement on a per- particle basis You can also create unique effects with Stencil and Optical FX utilities

Chapter Contents

Practical applications of each math utility

A general approach to using per-particles attributes The functionality of the Array Mapper and Particle Sampler utilities Uses for Stencil and Optical FX utilities

The purpose of Unit Conversion and other scene nodes

8