2. Basic Muscle Pass — Transcript

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1. 0:00okay let's start by diving into this
2. 0:01geometry object and we'll drop down the
3. 0:04capibara test
4. 0:06geometry with the capar asset we can
5. 0:09output the outer skin the muscle
6. 0:10surfaces bones and the animated skeleton
7. 0:13which we'll use shortly so let's switch
8. 0:15the output to muscles and then we can
9. 0:17convert these polygonal surfaces to
10. 0:19solids we'll use a muscle solidify node
11. 0:21to do that for us this node will Loop
12. 0:24through each of the connected pieces on
13. 0:25the incoming geometry and convert it to
14. 0:27tetrahedrons
15. 0:30um there are parameters here that allow
16. 0:31us to go in and change the resolution of
17. 0:34those tets um so for instance if I just
18. 0:37raise the minimum size slightly we're
19. 0:39going to get a slightly coarser model
20. 0:41but that should be sufficient for what
21. 0:42we're going to do here today now I might
22. 0:45also add that all the muscle tools that
23. 0:46we're going to be interested in can be
24. 0:48found by hitting the tab menu going
25. 0:50under character effects and then over to
26. 0:52the muscles subtab so everything we need
27. 0:55we'll find in this area here so while
28. 0:57we're here we're going to grab the
29. 0:59muscle solver node
30. 1:00which we can now drop down and append to
31. 1:02our
32. 1:05Network let that
33. 1:08initialize and if we look at the output
34. 1:12of this node here now um we're ready to
35. 1:15start simulating with this geometry um
36. 1:17let me just first turn on the ground
37. 1:19plane so that we have something to
38. 1:20collide with so if I run that um we
39. 1:24won't have much of a muscle
40. 1:25simulation going on as much as we do
41. 1:27just a bunch of soft body objects
42. 1:29falling to the floor and colliding with
43. 1:31each
44. 1:37other let me come over here and adjust
45. 1:39my frame
46. 1:46range and if we play
47. 1:49that like I said it's a uh just a
48. 1:52collection of soft body objects
49. 1:56falling so how do we get this to look
50. 1:58more like a muscle simulation
51. 2:00let's duplicate the capua asset and
52. 2:03switch the output to Bone
53. 2:06surfaces and this will now give us our
54. 2:09skeleton model which um is not animated
55. 2:13at all it's a static it's a static
56. 2:16skeleton and if we wire the output to
57. 2:19the second input on the muscle solver
58. 2:22the second input is expecting the
59. 2:24attachment Target for the
60. 2:26muscles and maybe we can play our
61. 2:28simulation at this point to to get an
62. 2:30idea of where things
63. 2:41are and now we get a new Avalanche of
64. 2:43soft body objects this time finding new
65. 2:46Collision geometry on its way
66. 2:49down so let's take this one step
67. 2:53further let's come back over to our
68. 2:56solid muscles and let's layer on some
69. 2:58attributes that will inform the muscle
70. 3:01solver node how to configure the
71. 3:03constraints that will attach to the
72. 3:05bones so we'll drop down a muscle
73. 3:07constraint properties
74. 3:09node and as we wire that in um we'll
75. 3:13save the details for exactly how the
76. 3:15muscles relate to the bones um for later
77. 3:18on in the video series for now we'll
78. 3:20just U connect it to the muscle solver
79. 3:23and just get the default values to work
80. 3:26for us for this example
81. 3:30Let's uh hit play and see where our
82. 3:31simulation goes
83. 3:36next and as that solving already we can
84. 3:39see that the muscles are no longer
85. 3:40falling
86. 3:42off they are um they are keeping an
87. 3:45attachment somewhat springy but um again
88. 3:48nothing's been tweaked at this
89. 3:50point okay so let's continue to build on
90. 3:53this and maybe we can add some more
91. 3:55movement as things currently stand we're
92. 3:58using the static non at output from the
93. 4:00capar asset to give us our
94. 4:03skeleton um but this asset does give us
95. 4:05animated joints on the second and third
96. 4:08outputs so what we can do is drop down a
97. 4:10joint to form
98. 4:13node and as we wire that
99. 4:17up all of a sudden now we see we have
100. 4:20animation on our
101. 4:24skeleton now normally we'd be able to
102. 4:26take this animated skeleton and feed it
103. 4:28directly into the muscle solver but
104. 4:29there is a small issue that we're going
105. 4:31to need to address before moving on if
106. 4:33we look at the components as they arrive
107. 4:36into the muscle solver uh we see that
108. 4:38the initial position for the bones and
109. 4:40the muscles no longer sink up and this
110. 4:43is due to the skeleton geometry coming
111. 4:46from an animated position right from
112. 4:48frame one and the muscles being set up
113. 4:52in uh the rest
114. 4:54position to fix this we'll need to
115. 4:56intercept The Joint animation coming out
116. 4:58of the third input and transition into
117. 5:01it from the rest position so we'll use a
118. 5:04skeleton blend soap here to blend from
119. 5:07the tpost position into the animated
120. 5:11output and we can simply key frame that
121. 5:15transition so that at the first frame
122. 5:18we're at a weight of zero I.E the rest
123. 5:21pose and by frame five let's say we
124. 5:23transition fully into our animated
125. 5:26joints
126. 5:29confirm that the transition is
127. 5:31working and if we look at the initial
128. 5:34setup for the muscle
129. 5:37solver we are
130. 5:39now back in business we'll start the
131. 5:42simulation up and we can see now that
132. 5:45the muscles are staying attached to the
133. 5:48animated bone
134. 5:52positions that's looking pretty springy
135. 5:55and loose as far as an attachment goes
136. 5:57so maybe we can tweak that a little bit
137. 5:59just before we we move
138. 6:00forward we'll come back up here to the
139. 6:02muscle constraint properties and I'm
140. 6:05just going to go over to the um muscle
141. 6:07to Bone Tab and enable the stiffness
142. 6:11parameter let's see what a stiffness
143. 6:13value of 10 is going to give us come
144. 6:16back to the solver node run that one
145. 6:19more
146. 6:20time and sure enough that has stiffened
147. 6:22up the constraints quite a bit so this
148. 6:24is a constraint that's attaching each
149. 6:26muscle to whatever bone it finds in the
150. 6:29in its vicinity and uh by stiffening it
151. 6:32up we've um removed a lot of the springy
152. 6:36quality that the muscle to Bone
153. 6:38attachments
154. 6:39had so maybe the stiffness here is a
155. 6:42little too high uh we may want to bring
156. 6:44back a little bit of the bounce and uh
157. 6:47just relax that spring a little bit so
158. 6:49let's do that once again come back up
159. 6:51here let's say take that down to
160. 6:58five and we'll run it once
161. 7:03more so that's looking a little more
162. 7:06Dynamic we're getting some bounce and
163. 7:08some secondary
164. 7:13motion so I'm just about to run my
165. 7:15simulation and write the output to disk
166. 7:17I've added a file cache node here to
167. 7:19capture the output but before I do that
168. 7:21there's um uh one or two things we want
169. 7:23to just talk about real quick here um
170. 7:26the uh when the when the muscle solver
171. 7:29uh config figures its constraints it
172. 7:30does this by um going back to a rest
173. 7:34position so it takes away your animation
174. 7:36puts your gometry in the rest position
175. 7:38and configures the constraints there the
176. 7:41uh the rest position by convention is
177. 7:43something we're calling T pose now where
178. 7:45is T POS coming from uh for starters on
179. 7:47the muscle solver if we scroll down we
180. 7:50see here that under rest position the
181. 7:52muscle solver is expecting to find a
182. 7:53toose attribute on the muscle input and
183. 7:55a separately named toose attribute on
184. 7:57the bones now the muscle input
185. 8:00um if we look at from the point when we
186. 8:01solidified the geometry that toose
187. 8:04attribute was generated for us
188. 8:05automatically so basically it's
189. 8:06capturing the construction position for
190. 8:09all the data and and storing it as a
191. 8:12rest position named to POS on the bone
192. 8:15side uh since the source of the bones
193. 8:18could be from anywhere um we need to
194. 8:20ensure that the attribute is placed
195. 8:22there
196. 8:23manually by by default if the uh solver
197. 8:27does not find uh these attributes the
198. 8:31the rest position attributes it will use
199. 8:33the start frame the initialization frame
200. 8:36here as though it were the T POS so it
201. 8:38will um Park everything at this Frame
202. 8:40construct the constraints and Carry On
203. 8:42from there um but let's put in a a t POS
204. 8:46attribute in here explicitly so to do
205. 8:48that we simply um append
206. 8:51um um a modified version of the rest
207. 8:54position swap that we find here under
208. 8:57this tool called set T pose
209. 9:01and what it's doing is it's simply
210. 9:02capturing the uh incoming position as a
211. 9:05rest attribute naming it t pose so now
212. 9:07as this data flows through um the muscle
213. 9:10solver will find the T pose and make all
214. 9:12the necessary connections as it did
215. 9:14before and just before we run our
216. 9:16simulation and save it out the output
217. 9:19from the muscle solver included uh all
218. 9:22the original attributes and U groups
219. 9:25that were necessary for it to run um as
220. 9:27we move forward into the next pass for
221. 9:29the tissue solver those attributes and
222. 9:32groups are no longer
223. 9:34needed also we only really need
224. 9:36polygonal geometry uh when we get to our
225. 9:39tissue pass so we're going to go ahead
226. 9:40and convert the tetrahedrons to polygons
227. 9:42as
228. 9:44well okay so for the cleanup um as I
229. 9:47said we are converting uh our tits to uh
230. 9:51polygon so what we end up with here are
231. 9:54just the polygonal shells that surround
232. 9:55our our muscles um we're going to delete
233. 9:58all attributes so I've used this syntax
234. 10:00here to just basically say clear out all
235. 10:02attributes and if you notice here we're
236. 10:04saying everything except the T POS
237. 10:06attribute we're going to hang on to that
238. 10:08now a word about that the um you may
239. 10:11find it's more efficient to uh save out
240. 10:15your T pose separately and then uh
241. 10:17reapply it uh later on as I'm writing
242. 10:20out a full sequence of uh the simulation
243. 10:23frame by frame every single frame in my
244. 10:25case is going to contain data that
245. 10:27represents the T pose and it doesn't
246. 10:28change so so uh you can choose to uh
247. 10:31have a more efficient workflow if you
248. 10:32like but for for my purposes this is
249. 10:35just a test so uh we're going to just
250. 10:37make it simple do that uh and then
251. 10:39finally uh removing any groups uh again
252. 10:42we don't need anything so we've
253. 10:43basically stripped everything down uh
254. 10:46very close to the bare minimum
255. 10:47here uh also I've um just simply renamed
256. 10:51uh this file cache node as a name that I
257. 10:54can easily reference later on and I've
258. 10:56appended a null sop to our bone anim so
259. 10:59that that can also be referenced and
260. 11:01easily uh retrieved when we need it from
261. 11:04our second pass so let's uh run our
262. 11:07simulation and uh move forward