rig soft forms in blender

An­i­mate a lion’s mane jel­ly­fish, de­rived from a loop­ing in­stal­la­tion orig­i­nally cre­ated for an aquar­ium

3D Artist - - CONTENTS -

So when a client comes to you ask­ing for a seam­less loop of a near pho­to­real jel­ly­fish, to be cre­ated en­tirely in Blender, you know that you’re go­ing to have to find some pretty smart so­lu­tions to some pretty big prob­lems. like how do you be­gin to man­u­ally an­i­mate a thou­sand ten­ta­cles? (Be­cause there’s no way to make a sim­u­la­tion that com­plex loop flu­idly; not to men­tion how to man­age all the in­ter­sec­tion er­rors.) And how do you rig an amor­phous blob to move in such a par­tic­u­lar way? over the next 15 steps you will learn the over-arch­ing principles and main tech­niques of how you can rig a jel­ly­fish, or any amor­phous blob, while still keep­ing the rig light­weight and kind to your CPU.


Do your home­work and study ref­er­ences get to know the crea­ture you’re rig­ging, and be­come fa­mil­iar with how it moves. don’t just study a video, use Blender’s grease Pen­cil tools to ro­to­scope (trace) a video frame by frame. this not only gets you used to the un­du­lat­ing mo­tion of the jel­ly­fish, it can also be used as ref­er­ence in­stead of the video, should the video play­back prove too CPU heavy for your view­port. Vi­tal to the suc­cess of a project like this is be­ing eco­nom­i­cal with com­puter power. Af­ter all, if it doesn’t play­back smoothly, it’ll be im­pos­si­ble to an­i­mate, and we don’t all have the lux­ury of work­ing on su­per com­put­ers. Ad­di­tion­ally, grease Pen­cil an­i­ma­tions can be moved to wher­ever it is that you need them, mak­ing them rather ver­sa­tile in projects.


Work­bench setup tip if you fix a car you prob­a­bly shouldn’t at­tempt to fix it while it’s still mov­ing. it’s best prac­tice to work on it in a garage. like­wise, when you rig a crea­ture, it’s good to set up a ‘work­bench’ space. to do this, give the ar­ma­ture (and any sep­a­rate or ad­di­tional parts) a ‘child of’ con­straint and point it to an empty or null. this mas­terempty is what you an­i­mate to move the crea­ture around the scene. this way you can cre­ate a test an­i­ma­tion with the rig and see it mov­ing in situ. But then by slid­ing the ‘child of’ con­straint’s in­flu­ence to zero, you can have your rig in the cen­tre of the scene with all its axis aligned to the scene and or­tho­graphic cam­eras, per­fect for a clean and or­derly way of mod­i­fy­ing a rig. then with a snap of the in­flu­ence slider you will be test­ing the mod­i­fi­ca­tions in situ once more.


Set up the work­bench driver As the crea­ture be­comes more com­plex, you’ll likely need mul­ti­ple ‘child of’ con­straints for each part (de­pend­ing on your hi­er­ar­chy). so it’s a good idea to set up a cus­tom prop­erty on your mas­terempty – the prop­erty should be called some­thing like ‘par­ent­ing’ and have a range of 0-1. then we can add a driver to each of the ‘child of’ mod­i­fier’s in­flu­ence slid­ers. now the ‘par­ent­ing’ prop­erty will af­fect all the ‘child of’ mod­i­fiers at once.


Bone setup let’s look at rig­ging the bell, the main sec­tion of the crea­ture. We need bones, but we want as few con­trols as pos­si­ble, to achieve max­i­mum vari­ance. We will cre­ate a chain of reg­u­lar bones to guide a few ‘bendy bones’ to de­form the mesh. Cre­ate an ar­ma­ture, call it ‘jel­ly_rig’. Cre­ate a ‘Root’ bone, point­ing up­wards. then cre­ate a bone a lit­tle be­low that, also point­ing up called ‘bel­l_­peak’. from the base of bel­l_­peak ex­trude a bone along the -x axis (call it ‘Up­per’), and another from the tip of that one (call it ‘lower’). from each of th­ese ex­trude a small bone along the z axis. Call the one clos­est to the cen­tre ‘up­per_c­trl’ and ‘low­er_c­trl’. Par­ent each of th­ese to the ‘Root’ bone (keep off­set), also par­ent (keep off­set) bell_ peak to the ‘Root’, then Up­per to ‘bel­l_­peak’ (keep off­set).


Cre­ate bone con­straints give the Up­per bone a damped track con­straint and point at the ‘up­per_ ctrl’. give the lower bone a damped track con­straint and point at the ‘low­er_c­trl’. the ‘bel­l_­peak’ and ‘up­per_c­trl’ and ‘low­er_c­trl’ give you con­trol over this ar­ma­ture. the ‘root’ bone lets you po­si­tion the ar­ma­ture in the scene (this is mostly re­dun­dant due to us­ing the child of and ‘mas­terempty’ as in step 2 but is use­ful for hi­er­ar­chy as well as counter animating and fix­ing trou­ble dur­ing an­i­ma­tion).


De­form bendy bones let’s ex­trude another bone from ‘bell peak’ (call it ‘up­per.def’), go­ing along the same axis as the up­per bone and reach­ing the same point. ex­trude another from ‘up­per.def’s’ tip, fol­low­ing the same axis and length as lower bone (call this ‘lower.def’). make both ‘bendy bones’ by adding six seg­ments in the bendy bone op­tions. give the ‘up­per.def’ a stretch-to Con­straint tar­get the ‘up­per_c­trl’ bone. give the ‘lower.def’ a stretch-to Con­straint tar­get the ‘low­er_c­trl’ bone. th­ese bones now flex and fol­low the an­gu­lar bones, and can de­form our rig.


Screw mod­i­fier and mesh de­former How do we use a sin­gle chain of bones to ma­nip­u­late an en­tire mesh? start by cre­at­ing a sin­gle vert a lit­tle above the tip of the jelly’s bell, (call this ob­ject ‘Jel­ly­meshdef’) then ex­trude a line of verts around the ‘bell’s’ pro­file, a sin­gle edge of verts and edges. Add an ar­ma­ture mod­i­fier to this ge­om­e­try, point it to our ‘jel­ly_rig’. then Weight Paint the verts to the bendy bones. this means adding ver­tex groups with names ‘de­f_up­per’ and ‘de­f_lower’ and ei­ther paint­ing in val­ues in Weight Paint mode or se­lect­ing the verts that fall clos­est to the bone with a cor­re­spond­ing name and as­sign­ing a value of 1 to it. this line of verts and edges should fol­low the de­for­ma­tions of our ar­ma­ture. if we then add a screw mod­i­fier, to ‘spin’ the ge­om­e­try around 360, we have a bell shape that de­forms all the way around with only a sin­gle con­trol arm. Add a mesh de­form mod­i­fier to the main ‘bell’ ge­om­e­try and ‘bind’ it to the spun ‘Jel­ly­meshdef’ ge­om­e­try. the sin­gle chain of bones con­trols the en­tire bell ge­om­e­try.


Add va­ri­ety with Wave mod­i­fiers to add some un­even­ness and break up the sym­me­try, we can stack mul­ti­ple Wave mod­i­fiers on top of the mesh de­former. Re­mem­ber the Wave mod­i­fier is par­tic­u­lar about how it is used and along what axis it will work. for­tu­nately due to our dili­gence in step 2, the mod­i­fiers will oc­cur prior to the child of mod­i­fiers, en­abling us to set up our ge­om­e­try along the cor­rect axis to make use of the Wave mod­i­fiers.

Cre­ate a Bézier curve, sub­di­vided as much as you need and cre­ate hooks at each con­trol point. th­ese hooks will be how you con­trol the ten­dril an­i­ma­tions


Man­ual ten­dril sys­tem to make the ten­drils, cre­ate lines of verts and edges with no faces (along the y axis so we can use them with the Wave mod­i­fiers later). Have ten to 20 of th­ese lines in a sin­gle ob­ject and sculpt them to look like a slightly wavy group of hairs. Call this ob­ject ‘ten­drils’. Cre­ate a cir­cle mesh and ex­trude out some faces. Call this ‘ten­drilcol­lar’. then cre­ate a Bézier curve, sub­di­vided it as much as you need and use Cmd/ctrl+h to cre­ate hooks at each con­trol point. th­ese hooks will be how you con­trol the ten­dril an­i­ma­tions. Keep in mind that the more you sub­di­vide, the more op­tions you will have, but also the harder you will have to work to an­i­mate it. We set­tled for five con­trol points on our curve, with more of them close to the start of the curve to avoid mesh in­ter­sec­tions.


Cre­ate par­ent­ing ten­drils the first of th­ese hooks should be par­ented to the ten­drilcol­lar. the re­main­ing emp­ties and the ten­drilcol­lar, ten­drils and Bézier curve will all need a ‘child of’ con­straint (as in step 2). give the ten­drils a Curve mod­i­fier and point it to the Bézier curve. Re­po­si­tion the ten­drils to fix the off­set. the ten­drils should now de­form along the curve when you move the emp­ties. (once the mane is com­plete we will re­par­ent the col­lar).


Mod­i­fiers for ten­drils to give it some move­ment, add two Wave mod­i­fiers be­fore the Curve mod­i­fier. set one to work the x axis and one to work the y axis, set both to global and give them a cloudy tex­ture. this should cre­ate broad sway­ing mo­tions to em­u­late the un­der­cur­rent of the ocean. ex­per­i­ment with them to get the ef­fect you want. Cru­cially, we now need a dis­place mod­i­fier af­ter the Curve mod­i­fier, again use a cloudy tex­ture and set to global and ‘rgb to xyz’. this will cre­ate a tur­bu­lent ef­fect as the ten­drils move through space.


Fin­ish the ten­drils in order to keep the Wave and dis­place mod­i­fiers in check, Weight Paint a ver­tex group so that th­ese mod­i­fiers don’t af­fect the roots of the ten­drils. We can then add a sub­sur­face mod­i­fier to the stack to smooth the ten­drils out. We now have un­du­lat­ing ten­drils that can be an­i­mated man­u­ally. How­ever, as they have no faces they won’t ren­der, so add a screw mod­i­fier set to 0.4 de­grees to ex­trude out some faces, then add a so­lid­ify mod­i­fier to fin­ish off the ef­fect.


Du­pli­cate the ten­drils du­pli­cate the en­tire mass of ten­drils (ex­cept the col­lar) to another layer, re­par­ent­ing the first hook to a dif­fer­ent sec­tion of the col­lar. do this as many times as re­quired, re­mem­ber­ing you have to man­u­ally an­i­mate this… about ten of them did the job for us. this should re­sult in a full mane of ten­drils that can be man­u­ally an­i­mated, with a great deal of pro­ce­dural de­tails.

Put your cre­ation through its paces, par­tic­u­larly if you are cre­at­ing the rig for some­one else. no an­i­ma­tor wants to ex­pe­ri­ence a nasty sur­prise half­way through a project!


At­tach to the main rig now your mane of ten­drils is com­plete, at­tach them to the main rig. Put the rig in ‘work­bench’ mode (par­ent­ing to Zero) and go­ing back to the ‘Jel­ly_rig’, add a bone (called ‘skirt’) just be­low the ‘bell_ peak’ and par­ent it (with off­set) to the ‘bel­l_­peak’. this will now pre­vent the ten­dril roots from pen­e­trat­ing the bell ge­om­e­try, and fol­low its un­du­la­tion as you an­i­mate it. Be sure to test that you haven’t ‘or­phaned’ or ‘dou­ble par­ented’ any­thing. this means that when you ad­just the ‘par­ent­ing’ value, or­phaned ob­jects will not move and dou­ble par­ented ob­jects will shoot off ran­domly. or­phans need par­ent­ing or ‘child of’ mod­i­fiers, whereas dou­ble par­ents prob­a­bly have a ‘child of’ mod­i­fier (or Curve mod­i­fier) as well as a par­ent, so its in­her­ited trans­la­tion (move­ment) is dou­bled. to fix this, try un­par­ent­ing it.


Test and test again! Put your cre­ation through its paces, par­tic­u­larly if you are cre­at­ing the rig for some­one else. no an­i­ma­tor wants to ex­pe­ri­ence a nasty sur­prise half­way through a project! it may be pru­dent to lock the locrot and scale of any val­ues of any ob­ject in the rig that you don’t want to be tam­pered with. now’s a good time to re­view what you want to achieve with your rig and con­sider adding, or even scrapping parts of the rig that don’t fit with your work­flow. You can also think about chang­ing bone shapes to make the con­trols eas­ier to recog­nise.

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