Utility Nodes in an Animation Pipeline

1. Utility Nodes in an Animation Pipeline Joe Harkins Creature Technical Director Tippett Studio

2. Definition: node • A construct that holds specific information, along with the actions associated with that information. WHAT IS A UTILITY NODE?

3. Definition: utility node • A node that allows the creation of specific shading effects, most commonly used in shading networks. • They are sometimes referred to as “math nodes”. WHAT IS A UTILITY NODE?

4. Definition: attributes • a slot in a node that can hold a value or a connection to another node. Attributes control how a node works. WHAT IS A UTILITY NODE?

5. Definition: Input • two types of numerical inputs: static, dynamic. • dynamic input • updates in real-time as the upstream connection changes. • static input • does not change and is not connected to any other nodes WHAT IS A UTILITY NODE?

6. Definition: Operator • operation: mathematical function • Usually determined by the type of node you have created. The process of combining inputs and performing a mathematical function. WHAT IS A UTILITY NODE?

7. Definition: Output • output: dynamic result of the operation • An output attribute's job is to hold the result of the operation from the utility node. The real-time capability means that the output attribute is always accurate. WHAT IS A UTILITY NODE?

8. Definition: Compute • compute: hidden function • Each node in Maya must take the attributes associated with it and compute them to give you an output. The output is the dynamic result of the operation, but the operation is the result of a computation that must be made within Maya. WHAT IS A UTILITY NODE?

9. disadvantage: no string inputs • No MEL commands • No text data • No variable storage advantage: reliable evaluation Updates with the dependency graph in real-time. Evaluation is reliable to upstream connections. Advantages &Disadvantages

10. advantage: evaluation speed • using an expression with commands like "getAttr" and "setAttr" is going to be slower than using a utility node with direct connections to perform the same operation. Expressions take longer to evaluate because they contain code. That code must then by parsed and evaluated by the processor. A node is a simple mathematical operation that has a specific function and requires no preprocessing. Advantages &Disadvantages

11. disadvantage: MEL dependency • most utility nodes must be created manually using MEL. • Some nodes can be created within the Hypershade window. Advantages &Disadvantages

12. advantage: flexibility • Utility nodes can be quickly edited with MEL. advantage: technical control Utility nodes can essentially be locked down and require a certain amount of effort to change. Advantages &Disadvantages

13. disadvantage: archaic naming • What if you don't know what kind of node you need? • Why is it called “addDoubleLinear”? • Why are there so many different nodes? • When in doubt - press F1 Advantages &Disadvantages

14. advantage: functionality advantage: not name dependant Unaffected by referencing, namespaces, script errors, or variables changes. advantage: keyable dynamic attributes Any input from a utility node can accept keyframe animation. Advantages &Disadvantages

15. Utility Node Creation • MEL Commands you need to know… • createNode • the "createNode" command will allow you to create any type of node in Maya, for example, to create an "addDoubleLinear" type node, you would type the following into the script editor: • createNode "addDoubleLinear"; • It would be better to name the node something besides the default name Maya gives it, add the -n flag as follows: • createNode "addDoubleLinear" -n "add1"; • connectAttr • This command would connect objectA's translation in the X axis to the first input of the "add1" utility node that was created using the createNode command above: • connectAttr "objectA.translateX" "add1.input1"; • setAttr • If the attribute is static you only need to set it initially at time of creation. Do this with the setAttr command on the utility node as follows: • setAttr "add1.input2" 5; Utility Nodesand MEL

16. MEL Flow Control • for loops • MEL offers a very convenient way to parse through the selection list by using for loops to break the list of objects (ie: a string array) down to per-item manipulation. • $listOfThingsSelected=`ls -sl`; • // Note that if listOfThingsSelected hasn't been declared yet, • // it will be dynamically typed based on the result of the "ls" command. • for ($i=0; $i < size($listOfThingsSelected); ++$i) • { • print $listOfThingsSelected[$i]; • } • Alternatively, this does the exact same thing: • string $listOfThingsSelected[] =`ls -sl`; • for ($thing in $listOfThingsSelected) • { • print $thing; • } Utility Nodesand MEL

17. MEL Flow Control • What is an array? • A list that can hold more than one value. The array assigns each value its own place in line which will allow you to call individual items from the array with ease. • string $listOfThingsSelected[] =`ls -sl`; • for ($thing in $listOfThingsSelected) • { • createNode addDoubleLinear -n ($thing + "addMe"); • } Utility Nodesand MEL

18. MEL Flow Control • To connect the attributes for each item in the array to the node and vice versa let’s take the loop one step further: • string $listOfThingsSelected[] =`ls -sl`; • for ($thing in $listOfThingsSelected) • { • createNode addDoubleLinear -n ($thing + "addMe"); • connectAttr ($thing + ".translateX") ($thing + "addMe.input1"); • connectAttr ($thing + ".translateY") ($thing + "addMe.input2"); • connectAttr ($thing + "addMe.output") ($thing + ".translateZ"); • } • select $listOfThingsSelected; • A procedure is a collection of MEL commands that can be accessed by executing the name of that procedure (and any associated arguments) . • proc createAddNode () • { • string $listOfThingsSelected[] =`ls -sl`; • for ($thing in $listOfThingsSelected) • { • createNode addDoubleLinear -n ($thing + "addMe"); • connectAttr ($thing + ".translateX") ($thing + "addMe.input1"); • connectAttr ($thing + ".translateY") ($thing + "addMe.input2"); • connectAttr ($thing + "addMe.output") ($thing + ".translateZ"); • } • select $listOfThingsSelected; • } Utility Nodesand MEL

19. MEL Flow Control • If/else statements • Conditional statements allow you to choose which items in the array will be affected by the procedure. • proc createAddNode () • { • string $listOfThingsSelected[] =`ls -sl`; • for ($thing in $listOfThingsSelected) • { • if(`nodeType $thing` == "joint") • { • createNode addDoubleLinear -n ($thing + "addMe"); • connectAttr ($thing + ".translateX") ($thing + "addMe.input1"); • connectAttr ($thing + ".translateY") ($thing + "addMe.input2"); • connectAttr ($thing + "addMe.output") ($thing + ".translateZ"); • } • else print ($thing + " is not a joint, skipping! \n"); • } • select $listOfThingsSelected; • } Utility Nodesand MEL

20. GUI Implementation • Combining commands • There are only three MEL commands needed to control the nodes during creation. • Worry about the methodology used to create the nodes themselves. • Goal is to have a script with procedures that are robust, easy to understand, and offer flexibility during use. • Interactive window • Avoid name specific scripting. • Use input data from fields to define variables. • Name all of your fields appropriately for querying data within the procedure. Utility Nodesand MEL

21. GUI Implementation • Extracting data from the GUI • global proc createAddNode () • { • string $listOfThingsSelected[] =`ls -sl`; • string $input1 = `textField -q -tx adl_input1`; • string $input2 = `textField -q -tx adl_input2`; • string $output = `textField -q -tx adl_output`; • for ($thing in $listOfThingsSelected) • { • if(`nodeType $thing` == "joint") • { • createNode addDoubleLinear -n ($thing + "addMe"); • connectAttr ($thing + "." + $input1) ($thing + "addMe.input1"); • connectAttr ($thing + "." + $input2) ($thing + "addMe.input2"); • connectAttr ($thing + "addMe.output") ($thing + "." + $output); • } • else print ($thing + " is not a joint, skipping! \n"); • } • select $listOfThingsSelected; • } Utility Nodesand MEL

22. Utility Creator MEL Script Utility Nodesand MEL

23. Rigging Solutions • Expression Replacement • An example of an expression that could be replaced with a utility node: • objectA.translateX = objectB.translateX * .75; • MEL code to create a multDoubleLinear node doing the equivelent would be: • string $mdl = `createNode multDoubleLinear`; • connectAttr "objectB.translateX" ($mdl + ".input1"); • setAttr ($mdl + ".input2") .75; • This is another example, only slightly more complex; first the expression: • float $tx = `getAttr objectB.translateX`; • float $ty = `getAttr objectB.translateY`; • objectA.translateX = ($tx + $ty)* .75; • The MEL code for utility node conversion would be: • string $adl = `createNode addDoubleLinear`; • string $mdl = `createNode multDoubleLinear`; • connectAttr "objectB.translateX" ($adl + ".input1"); • connectAttr "objectB.translateY" ($adl + ".input2"); • connectAttr ($adl + ".output") ($mdl + ".input1") ; • setAttr ($mdl + ".input2") .75; • connectAttr ($mdl + ".output") "objectA.translateX"; Defining Areas of Use

24. Rigging Solutions • Joint Dampening – multDoubleLinear node • Joint’s rotation is multiplied by a driving joint for a final output. • Output is then input to the hierarchy above the driven joint for indirect manipulation. • Can be gradually dialed on, or turned off to have no effect. Defining Areas of Use

25. Rigging Solutions • Joint Averaging • query the distance between two locators, then divide the distance by the number of joints and input into each joint’s translation using a multiplyDivide node. • joint.translate = locator.translate / number of joints Defining Areas of Use

26. Rigging Solutions • Custom Driven Attributes • Useful for driving blendShapes or changing the range of an existing attribute for greater control. • Output = Min + (((Value-OldMin)/(OldMax-OldMin)) * (Max-Min)) Defining Areas of Use

27. Rigging Solutions • FK/IK Switching • Requires 3 separate chains: driven, FK, IK • Connecting the driven skeleton to the driving FK and IK skeletons using • a blendTwoAttr node will allow animation blending between the two chains. • Use a custom attribute, connected to the attributeBlender of the node, as a driver. Defining Areas of Use

28. Rigging Solutions • FK/IK Switching Defining Areas of Use

29. Animation Solutions • Animation Blending • Able to be added nondestructively. • blendColors node is a good choice for this simple operation. • can take up to six inputs, two for each channel, R, G and B respectively. It also has one input called “blender”, which can be connected to a user added attribute to control the blending. • Here’s the code you would need to create the connections for channels that exist on selected objects: • string $all[] = `ls -sl`; string $each; string $blender = "blendObject.blendAttribute"; for ($each in $all) • {string $blendColors = `createNode blendColors`; connectAttr $blender ($blendColors + ".blender"); connectAttr ($each + ".rx") ($blendColors + ".c1r"); connectAttr ($each + ".ry") ($blendColors + ".c2r"); connectAttr ($blendColors + ".opr") ($each + ".rz"); • } • Here is the formula used for color blending: • output[i] = Color1[i] * Blender[i] + Color2[i] * (1.0 - Blender[i]) Defining Areas of Use

30. Animation Solutions • Noise Animation • Able to be added nondestructively. • unlike blending - is mulitplied in an additive fashion. • Uses a hierarchy based system to avoid locking off channels. • multDoubleLinear gives us ( A * B = C ) • A = noiseCurve (driving animation curve) • B = noiseMult (to control input of noiseCurve) • C = output to an identical channel one node above in the hierarchy. Defining Areas of Use string $all[] = `ls -sl`; for ($each in $all){ string $noiseNodes[] = `listRelatives -p -pa $each`; string $noiseNode = $noiseNodes[0]; string $mdl = `createNode multDoubleLinear`; string $inChan[] = `channelBox -q -sma mainChannelBox`; for ($channel in $inChan){ catch (`addAttr -ln ($channel + "_noiseCurve") -k 1 $each`); catch (`addAttr -ln ($channel + "_noiseMult") -k 1 $each`); connectAttr ($each+ "." + $channel + "_noiseCurve") ($mdl + ".i1"); connectAttr ($each+ "." + $channel + "_noiseMult") ($mdl + ".i2"); setAttr ($each+ "." + $channel + "_noiseMult") 1; connectAttr ($mdl + ".output") ($noiseNode + "." + $channel);}}

31. Animation Solutions • Noise Animation - noiseMaker MEL Script Defining Areas of Use

32. Animation Solutions • Noise Animation - noiseMaker MEL Script • Randomly generated noise animation • for($frame=$start;$frame<=$end;$frame+=$step) • { • currentTime $frame; • $rand = `rand $min $max`; • setAttr ($obj + "." + $channel + "_noiseCurve") $rand; • $noise = `getAttr ($obj + "." + $channel + "_noiseCurve")`; • setKeyframe -v $noise -at ($channel + "_noiseCurve") $obj; • } • checks to see if you want the generated curve to cycle infintely and if you want it to be locked so you can't accidently set new keyframes on it: • if ($cycle == 1) setInfinity -poi cycle -at ($channel + "_noiseCurve") $obj; • if ($lock == 1)setAttr ($obj + "." + $channel + "_noiseCurve") -lock 1; Defining Areas of Use

33. Cyclic Animation • Animation Cycles - noiseMaker MEL Script • if ($copy == 1) • { • if (!`isConnected ($bta + ".output")($obj + "." + $channel) `) • { • copyKey -attribute $channel -option curve $obj; • CBdeleteConnection ($obj + "." + $channel); • pasteKey -attribute ($channel + "_noiseCurve") $obj; • } • } • You could combine the result with other cycles by using the blendColors or blendTwoAttr node, allowing you to blend between cycles quickly. The advantage, again, is the nondestructive additive nature of the multiplying and blending. Since we are not actively locking any attributes you can continue to animate normally. • If you are connecting two rigs together via constraints then the noise added to a loRes rig would transfer to the highRes rig without the need to add extra nodes to the highRes rig. ComplexSituations

34. Cyclic Animation • Offseting the Cycle - noiseMaker MEL Script • add time + user input to animation curve • addDoubleLinear.output = offsetAttr + time1.outTime • addDoubleLinear.output is connected to driverAttr • driverAttr <-> animCurve.input • multDoubleLinear.output = animCurve * noiseMultiplier • multDoubleLinear.output <--> final result • Connection must be forced in Maya • The –f flag tells Maya to break any connection • to the defined attribute and then force it to connect • to the one we want: • connectAttr -f objectA.driver objectA _animCurve.input; ComplexSituations

35. Advanced MEL Discussion • Custom attribute noise • Non-hierarchy based noise animation • noiseMaker will check any user defined attributes on the loaded objects to find out if the loaded attribute is custom and needs a special setup. If the custom attribute query returns true then the script will copy your animation curve, if any exists, onto an attribute named "custom attribute name + old" which can be used to blend between the old animation and the noise curve. • Here's how it breaks down: • customAttrA_blendDriver = customAttrA_noiseCurve * customAttrA_noiseMult • customAttrA_oldCurve is a copy of any existing animation on customAttrA • customAttrA_oldCurve and blendDriver are then blended together with the • customAttrA_blendOld attribute and finally output back to customAttrA • Here’s the code to show what’s going on in the script: • $mdl1 = `createNode multDoubleLinear`; • $bta = `createNode blendTwoAttr`; • addAttr -ln ($attr + "_oldCurve") -k 1 $obj; • addAttr -ln ($attr + "_blendOld") -k 1 $obj; • addAttr -ln ($attr + "_blendDriver") -k 1 $obj; • catch (`copyKey -attribute $attr -option curve $obj`); • catch (`CBdeleteConnection ($obj + "." + $attr)`); • catch (`pasteKey -attribute ($attr + "_oldCurve") $obj`); • connectAttr ($mdl1 + ".output") ($obj + "." + $attr + "_blendDriver"); • connectAttr ($obj + "." + $attr + "_blendDriver") ($bta + ".input[0]"); • connectAttr ($obj + "." + $attr + "_oldCurve") ($bta + ".input[1]"); • connectAttr ($obj + "." + $attr + "_blendOld") ($bta + ".ab"); • connectAttr ($bta + ".output") ($obj + "." + $attr); ComplexSituations

36. Advanced MEL Discussion • Replacing Math Cycles • Advanced expression replacement • 1. Evaluate what the expression is doing • breathroot1.scaleX=1+cos(time/breathcontrol.translateY)/10; • breathroot2.scaleX=1+cos(time/breathcontrol.translateY)/10; • In this case the expression is using the COS function to create rythmatic breathing by using inputs from translation of a locator. • 2. Determine whether or not the function is cyclic • 3. If cyclic returns true, create the cycle with an animation curve • 4. Setup cycle animation with utility nodes to mimic math function • string $multDivide = `createNode multiplyDivide`; • setAttr ($multDivide + ".operation") 2; • connectAttr "time1.outTime" "breathCurve.time"; • connectAttr "breathCurve.time" ($multDivide + ".i1x"); • connectAttr "breathcontrol.translateY" ($multDivide + ".i2x"); • connectAttr -f ($multDivide + ".outputX") "breathCurve_scaleCurve.input"; • string $mdl = `createNode multDoubleLinear`; • string $adl = `createNode addDoubleLinear`; • connectAttr "breathCurve.scaleCurve" ($mdl + ".i1"); • setAttr ($mdl + ".i2") .1; • connectAttr ($mdl + ".output") ($adl + ".i1"); • setAttr ($adl + ".i2") 1; • connectAttr ($adl + ".output") "breathroot1.scaleX"; • connectAttr ($adl + ".output") "breathroot2.scaleX"; ComplexSituations

37. Utility Nodes in an Animation Pipeline Thank You!