Rigging with Jason Schleifer

So I got a new job (yey =D) as a 3D generalist at Golden sq post, so Im a happy man, but I haven't really had any time to draw anything for my self, so no image update this week (nor last week it seems =P). I have been doing some rigging this week and I came across this wonderful tutorial called Animator Friendly Rigging by Jason Schleifer, a man who has worked on e.g. the Lord of the Rings. In this tutorial he goes through the principles of rigging and creates a complex production ready rig in Maya, but these principles of course are the same for any rig regardless of the software. The tutorial is around 10h long and comes with a 1500 page manual, so you can imagine that it is very detailed.

Here is a small example how he creates the base of a stretchy ik arm system with Maya. This follows closely his tutorial and all the credit goes to Jason for the principles and ideas, the only difference is that instead of mel expressions to control the stretchiness I have created connections in the hypergraph to do this (this should make the calculations faster, even thought the way he does it is not heavy in the first place).

1.First create 3 joint joint chain (best done in the side of front view) so that you will end up with something that looks like upper arm and forearm with a slight bend in the middle. You can name the joints up_arm, low_arm and hand. I have snapped the first joint in the side view to the grid position x=0 y=8 z=0 and the second randomly slightly to the left and lover around x=0 y=4 z=1 and the last joint to the centre of the world x=0 y=0 z=0.

2.Next create an ik system for the arm, by clicking Skeleton> IK Handle Tool and then by selecting your first join (up_arm) and then your last joint (hand).

3.Now you should have base for a normal working ik hand. Now create a locator and parent the ik handle to the locator, by first selecting the handle and then the locator and pressing [p]. You can rename the locator arm_loc and you should now be able to control the ik movement of the arm with this locator.

4.Now to the stretchy part. Maya evaluates the length of a bone by the distance of the joints child joint. In other words you can see the length of your upper_arm from the translate x value of your low_arm joint and we can also control the length of the upper arm by the translate x value of the low_arm joint. Same goes of course for the fore arm and the position of the hand joint

Just to make clear, even though maya displays bones between the joint balls, these balls are the actual joints. Easily demonstrated if you create a 2 joint joint-chain and then unparent the child by selecting it and pressing [shift+p], now you are left with 2 joints but no bone between them, so the bones are an extension of the joint and a visual representation of the joint hierarchy and these do effect the skinning of the character of course, but are not the joints them selves.

In order to know when to start the stretching of the arm we need to know the length of the whole arm which is of course the combined length of the upper arm and the fore arm. We can find these out from the child nodes of the upper arm’s and fore arm’s translation x values.

the length of the up_arm (upper arm) is the translation x value of low_arm and

the length of the low_arm (fore arm) is the translation x value of hand.

The arm needs to start to strech when the arm is completely straight witch means that the length after witch the arm needs to start to strech is the combined length of upper and lower arm ( low_arm.tx + hand.tx)

5. In order to know that we have reached the completely straight arm position we need to create something that measures the distance between the up_arm and the hand joint and when this value has reached the combined length of upper arm and fore arm we know that the hand is straight. We can do this by selecting Create > measure tool > distance tool. Now click on two places on the grid to create 2 locators and you can see that they are connected with a vector  and a value that displays the distance between the two locators. Now parent the first locator to arm_loc and then parent your up_arm(and of course the joint hierarchy with it) to the second locator. We do not want to parent the second locator to the up_arm because we are to control the length of the joint with the distance between the locators and this would be then affected by the up_arm and therefore it would create a loop. Now in my scene I get a value of 8 for the distance between the up_arm and hand when the hand is in its current slightly bend position.

6. In this example I will say that the translation x value of the low_arm is 4.3 and hand 4.5 so the full length of the arm is 8.8. If you want to know the exact values of your low_arm.tx you can type getAttr low_arm.tx to your Script editor and you will get a six decimal value for the translation value. We can now start to create the connections in the hypergraph. Now some people like to script things, but as I am more of a visual person I like to do things in the hypergraph rather than with mel if possible. So instead of doing Jason’s scripted set Driven Key system I have opted for mathematical graph system to do the same operations. Select your joints and your distanceDimensionShape (not just distanceDimension, but the actual shape node of it) and select input and output connections in the hypergraph.

So what we need to do is start to move the translate x values of the child joints to scale the joints as we move the arm locator, but we do not want to scale the joint smaller than their current value or other vice they will not bend at all but simply retain their current shape but get smaller. We also do not simply want to scale them up at their current position, so that the hand would not get straight ever. So we want the scaling only to happen when the arm is fully stretched to its maximum length, completely straight, but not before. We can do this by limiting the scale range with a clamp node to effect the arm only when the distance of the measure toll get bigger than the original length of the arm. You can get the clamp node from Rendering>create render node…and by selecting utilities and clamp. We can now make the following connections in order to create a system that outputs the translate x values to the joints.

We connect the measure tool’s distance to clamp node’s input R . We want to make the min value on the clamp 8.8 which is the full length of the arm so that the arm does not scale after the distance between the upper arm and hand goes below this value. We do not really want to put any limit on the scaling so we can connect the distance node to the max value so that as it gets larger so does the max limit, but what happens if the distance gets smaller? Our min is 8.8, but our max would be less than this (and the max value would over ride the min) so we need to make sure that the max value never gets smaller than 8.8 and we can do this by adding 8.8 (the full length of the arm when not stretched) between the distance node and the clamp max value. Now the clamp always outputs values between 8.8 and infinity.

Next we want to divide this value by the full length of the arm in its original form, so by 8.8. We do this with multiplyDivide node and connect the output of the clamp noted to the input1 x value of this node and in the input2 x value we type 8.8. Remember to change the operation from multiply to divide. Now we get values between 1 and infinity. These values are scale values, so that if the out put is 2 the translate x value(the length of the bone) should be twice as big. But in order to connect these values to the translate x value we need to multiply them with the original joint length for each joint as they have different lengths. We can do this with multiplyDivide nodes as well.

Create 2 more multiplyDivide nodes, one for each joint. Now connect the output value from the previous division operation to the input1 x value of both of these nodes. Next type the original length values (child joint translate x values) to the input2 x values of these nodes. In my example scene the values are 4.3 and 4.5 so one node has 4.3 and the other 4.5 in the input2.x. Now all you need to do is connect the multiplyDivide nodes to the corresponding joints translate x values. So in my case the node that had the multiply value of 4.3 to the low_arm.tx value and the one with value 4.5 to hand.tx.

Here are the actual connections (the hypergraph shows other nodes as well, but I have not mentioned them here as they are not relevant to the operation):

distanceDimensionShape1.distance->clamp1.inputR

distanceDimensionShape1.distance->addDoubleLinear1.input1

addDoubleLinear1.input1->clamp1.maxR

clamp1.inputR->multiplyDivide1.input1x

( typed in value of 8.8 -> multiplyDivide1.input2x)

multiplyDivide1.outputX->multiplyDivide2.input1x

( typed in value of 4.3-> multiplyDivide2.input2x)

multiplyDivide1.outputX->multiplyDivide3.input1x

( typed in value of 4.5-> multiplyDivide3.input2x)

multiplyDivide2.outputX->low_arm.translateX

multiplyDivide3.outputX->hand.translateX

Now if everything has gone as it should you should have an ik arm that works normally, but also stretches when the handle goes beyond the normal length value of the arm. This is great for cartoony animation or even if you just need a little bit of exaggeration for your normal character.

Jason continues the creation of the arm, hand and the whole body from here and also creates a separate fk system for each part (in fact he has 4 separate joint systems for the legs for optimal flexibility), so if you like what you have seen here I truly recommend that you will have a look at the complete Animator Friendly Rigging tutorial. Here is his website www.jasonschleifer.com.

Punk

Here's something I did this weekend as I was asked by an employer can I create somewhat realistic digital paintings. I decided to go for an old punk. I do admire people who have skills to do realistic paintings and drawings, but I rarely spend my precious time creating just realistic looking paintings as I feel that I can just go and take photo of a similar subject in a minute which would take hours to paint. Doing these kind of portraits is good practice though and when I embark to do one of these I try to pick a subject that is not too common, such as an old punk.

black lion update

I managed to refine the design today a bit. I decided to incorporate some polar bear and panther into the lion (with some fantasy element as well of course) and here is the result. Even though they are suppose to be the same animal I like the side view better as the mane is more smoky and less fire like although less mane like in general but ok in this case.

black lion

Ok, so I haven't managed to update my blog every week, the weeks just seem to fly by. Here is a creature that I have drawn couple of weeks ago. it is not finished as I have spend more time on practicing marker drawing here than actually concentrating on the design as I got new copic markers =). I have a fairly clear idea how I want it to look, I just need to decide on the details. The creature is going to resemble a lion but I do not tend to make it look exactly like one, I want it to have a bit more of a creature quality than an actual lion. It is going to be black and it is going to have a smoke or black fire mane and maybe some rune like patterns (not like the orange lines currently on one of the faces) on its skin, well see. Anyway this is what I have for now.

Birthday present

It is my girlfriend's birthday next week, but she will be visiting her parents on the actual day so I gave her my present already this week which is this picture. Her favorite animal is pig and she likes purple so this is her inner piggy in a secret forest garden.

Character designs

I have decided that I will try to update my blog bit more often (given that I have time), so I will try to post something every week. This week it is just some characters that I have drawn this week.