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3. Geometry Preparation for Muscle Sims — Transcript

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0:01so now that John has given a broad
0:02overview of the muscle setup we are
0:04ready to go into more step-by-step
0:07detail for each node I've also switched
0:10from the capara to this minur model as
0:14it has more complex muscles which will
0:16be better suited to our needs now the
0:19first thing we want to do is to make
0:20sure that our geometry is prepared
0:22correctly for the muscle simulation so
0:26let's start off by reading in the muscle
0:28model typically what you will do in a
0:31production situation is you will read a
0:33static muscle model from disk either as
0:38a USD file or an almic file perhaps fbx
0:42or bgo and that depends on your personal
0:45preferences but I will just show you
0:47some gotchas for those of you who are
0:50new to
0:50Houdini if you read in an almic file you
0:54will see we clicked on the info pane
0:57here we have 49 points
1:0049 Primitives and down here it shows
1:04that those 49 Primitives are packed
1:06almic now pack almic are very fast to
1:10read but they are not particularly
1:13useful for simulating so what we want to
1:16do is we want to get these into polygon
1:18form and so the best way to do that is
1:21with an unpack node
1:23now if you're reading in a USD file
1:27you'll want to use unpack USD instead
1:32or unpack USD to
1:34polygons but for almic just the unpack
1:36should be good and now you'll see that
1:40we have 13,000 and something points and
1:43Primitives and The Primitives of type
1:44polygon so that is excellent that is
1:47what we need however you might have a
1:49case where the almic was created by a
1:52different
1:53software you might still not have
1:56everything in polygonal form and in that
1:58case you'll want to add a con node after
2:01you're
2:02unpack and that will convert them to
2:05polygons and then you should be good to
2:08go so that is the first crucial step is
2:12to read in your geometry and make sure
2:14that it is in polygonal form the next
2:16step is to make sure that your model is
2:19in Scales of meters because many other
2:23software packages use centimeters as
2:26their default scale whereas Houdini uses
2:28meters and if you don't scale down your
2:31model the simulation will behave as if
2:34it is a giant so let's go into the front
2:37view with space bar
2:39three and with the Grid on got something
2:43else displayed so let me just hit Space
2:46by F to frame the muscles and we can see
2:52that this is 200 M tall which is
2:55definitely not what we want we want him
2:57to be about 2 m tall so I'm going to put
3:00drop down a transform
3:02node connect that up and to convert from
3:06ctim to meters we're going to set the
3:09uniform scale to 01 now it looks like
3:12it's disappeared but it's actually just
3:14down there so if I hit space bar F again
3:16it will frame in
3:18on the model and we will see that it is
3:21now 2 m tall which is perfect let me
3:24just remind you that if the rest of your
3:26production pipeline is working in centim
3:30units you will probably want to scale
3:32your final result back up again before
3:34you export it so then you will put down
3:37another transform node right at the end
3:39of
3:41everything before your whatever type of
3:44file caching you want to do and you will
3:47set your uniform scale to 100 and then
3:49that will scale it back up to the
3:51original scale that it
3:53was all right I will go back into
3:57perspective with space bar one
4:01and now let's look at our bones so for
4:05our rest bones we also want to make sure
4:08that it is in the correct scale as well
4:11as being
4:15polygons oh yes one thing I wanted to
4:18add uh don't get confused by this being
4:21by these being stash nodes
4:23basically in production environment you
4:26would use something like this what I
4:28have done is I've created created a
4:30stash node after I read my file in like
4:33this you see it's empty by default when
4:35you create it when you click stash input
4:37it will take whatever it's reading from
4:39disk here and save it into the file it's
4:42important to know that in
4:45Houdini when you're reading in a file
4:48it's not saving it into the hip file by
4:51default it's always just pointing to
4:53disk and loading it into memory as it
4:55reads it but if you want to actually
4:57save it into the file you use a stash
5:00node and click stash input now most of
5:02the time you would not do that the only
5:04reason I'm doing that is because I'm
5:05sharing this file online where it's
5:09easier to not have to worry about having
5:11a lot of external files along with the
5:14hip file to um pass along but if you on
5:18a shared network in a in a studio or
5:21something you will probably just read in
5:24files from disk so that is the logic
5:28behind why I have these stash nodes
5:32here okay so back to the
5:35bones so the bones need to have a t POS
5:38attribute now the muscles will
5:40eventually also get a t POS attribute
5:42but they will be created automatically
5:44by the muscle nodes but the bones need
5:47to have the T POS attribute created
5:49manually so the way you do this is if
5:53you press Tab and go to character
5:56effects muscles you will see
6:00that there
6:01is a set T pose
6:06option as well as an extract T pose
6:09option so let's start with the set T
6:13pose you'll notice is this is actually
6:15creating a node called rest position but
6:19the set T pose is an alias for the rest
6:22position node with the rest attribute
6:26already set to the name that the
6:30is expected by the muscle nodes which is
6:32T pose when you create a just a plain
6:34rest position
6:36node the default name for the rest
6:38attribute is
6:40rest it's completely fine to create a
6:44rest attribute node and manually change
6:47this to T pose I can see my
6:51keyboard
6:53but this Alias is just the helper for
6:56you to do it quickly
6:58okay so what this does is it takes
7:01whatever incoming position which is the
7:04P value the position is saved as a p
7:07point
7:08value into the P
7:11attribute and what this does is it takes
7:14whatever value is incoming in the P
7:16attribute and saves it to a an attribute
7:20called T pose and if we even look in the
7:23geometry
7:25spreadsheet we will see
7:30that
7:32the T
7:34pose attribute and P attribute
7:39match let's look at our bone animation
7:43so don't worry about the bone animation
7:45how I've set this up we just need to
7:49assume that you will have bone animation
7:51coming in in some form in this case
7:54because I've used the rest
7:55attribute and deformed it the the rest
7:58bones and have formed it to create my
8:01animation I already have a t pose
8:03attribute but let's say you're in a
8:06situation where your bone animation is
8:09coming in without a t POS attribute
8:12firstly let me just add that your bone
8:14animation and your T POS bones your rest
8:16bones should be blend shapable their
8:18point order must match but now let's say
8:22you have some type of animation and we
8:24need to set the T pose attribute so I'm
8:27going to say set T pose
8:31now in this case we have animated bones
8:37so we don't want to set the animation to
8:39the T pose that's contrary to what one
8:43would expect so what we're going to do
8:45is we're going to take the rest phones
8:47we're going to pipe it in as the second
8:49input and what it will do when there is
8:51a second input connected is it will save
8:54the P value of the second input into the
8:57T pose attribute instead
9:00so now we've created a toose attribute
9:03that is containing positional value of
9:07the second input even though the first
9:09input is dynamic now I mentioned earlier
9:14there's also the extract T POS now what
9:16the extract T POS does it's also an
9:18alias for the rest position node but
9:21here the mode is said to extract rest so
9:24what this does is it does the reverse so
9:27instead of saving the P value into T
9:30pose it's going to take the existing T
9:32pose value and replace the P value with
9:35that t pose value so now you see it has
9:39removed the animation the normals are
9:41still animating but the P
9:45value has been replaced with the static
9:48rest POS P so that's just to explain
9:52what these two nodes do in my case
9:55however my animation already has a t
9:57pose attribute so I don't need to worry
9:59about this but now we need to think
10:03about our pre-roll for the bones if
10:06you're lucky and you work in a pipeline
10:08where animation is exported with a
10:10pre-roll for you then that's great and
10:12you don't need to worry about this but
10:15that's not always the case so let's have
10:17a look at this Nifty little node and how
10:20it can help you so firstly for your
10:22muscle pre-roll you want to set your
10:24mode to blend into
10:26sequence when a parameter
10:29is bold like this it means it's not set
10:32to the default value so the default
10:34value is hold but instead we want to set
10:36it to blend into sequence next we'll see
10:39this T POS tab also is not set to
10:41default and that's because we've set it
10:44to use the attribute instead of initial
10:47frame because our initial frame on the
10:49animation isn't in the T pose so instead
10:52we're going to say use front attribute
10:54and the attribute will be called T pose
10:59now let's go to the main tab the first
11:03tab the initialization frame is the
11:07first frame of your animation or the
11:10last frame of your pre-roll so basically
11:14the pose that you want to grab from the
11:16incoming animation which you want to be
11:20the last frame of your pre-roll or we
11:23can let's say the target pose
11:26so here I've used frame 11 because in
11:29this case I set up the animation to
11:31start at frame 11 if you have got
11:33animation before frame 11 the pre-roll
11:36will just ignore
11:37it okay so I want
11:40my pre-roll to start uh sorry my
11:43pre-roll to end essentially on this
11:46Frame the initial hold is the last frame
11:49at which you want the T pose to be held
11:52at so all frames before this Frame will
11:56be on the T pose including this one and
11:58then from there on
11:59it will start blending to the
12:02initialization frame pose and the number
12:05of frames that that blend occurs over is
12:08going to be determined by the pre-roll
12:11duration so as you can see with this
12:14we're going to have it blend from T
12:17pose into that initialization frame and
12:20then the animation continues now I just
12:23want to point out something important if
12:25I template this incoming animation so
12:28that we can compare
12:30incoming animation to the pre-roll we
12:32see this matches perfectly and then
12:34obviously as we'd expect for the
12:36pre-roll part it will differ from the
12:41incoming
12:43but say you want to increase your
12:46initial
12:47hold right so what we have now is that
12:50we have until frame five we have the T
12:55pose being held and then we're going to
12:57have 10 frames of pre-roll
12:59but then that will overshoot our
13:01initialization frame so now our
13:04animation will no longer match the
13:06incoming animation after the
13:07initialization frame so to prevent that
13:10you need to make sure that these two
13:13numbers added together plus
13:16one adds up to the initialization frame
13:20so that means that if you want to give
13:22it an initial hold of five and you still
13:24want your animation to start on frame 11
13:27your pre-roll duration needs to decrease
13:29to five frames so now the animation
13:32lines up and we have a pre-roll of five
13:35frames here and a
13:38hold up to frame five here so just
13:42important to note that this is a frame
13:44number this is a number of frames this
13:46is a frame
13:47number let's show this in a more typical
13:50frame range for
13:52production so here I have my animation
13:56starting on frame 101
14:01one okay so what I want to
14:04do let's look at it here what I want to
14:08do is I want
14:10to have my pre-roll start on frame 990
14:14so I will set my initial hold to frame
14:15990 that's the last frame that I wanted
14:17to be on the T pose and I just realized
14:20I made a little mistake here when this
14:22was zero and
14:2410 um this isn't strictly speaking the T
14:28pose
14:30so just be aware of that I would either
14:31have to change this to zero or uh reduce
14:36increase this to frame one and reduce
14:38this to nine just to get it to be more
14:45accurate um but coming back to this one
14:48so in this case my animation is starting
14:51on
14:53frame1 my initial hold is frame 990 so
14:57that's the last frame that I wanted to
14:58be at T POS space where I have to frame
15:00it and then I'm going to let the
15:04pre-roll last for 10 frames so that this
15:07plus this is a th and then plus one
15:09equals that so that is perfect now it
15:11should line up great and you'll see if I
15:16increase
15:17this no longer lines up so this we will
15:21have to reduce to six to
15:25compensate all right so the more if your
15:29initialization frame is locked
15:31essentially if you want to add a longer
15:33pre-roll you will have to reduce your
15:36start frame numbers
15:38here okay let's go back to original
15:43file
15:45and now we have our bones with a
15:47pre-roll I can turn this template
15:53off now let's make sure that our muscles
15:59are correctly
16:02named now the important thing for the
16:05muscle names is that the muscle nodes
16:07expects the name to be stored as an
16:10attribute called musclecore
16:14ID and here looking at my
16:17incoming um
16:19attributes I see that I have a name
16:21attribute but I don't have a muscle ID
16:23attribute now in this case where there
16:26is a name attribute that's great I can
16:28just just very easily create a muscle ID
16:31from the name attribute and to do this
16:34I'm not going to use a muscle ID node
16:37okay it's very important you only need
16:39to use the muscle ID node if you don't
16:42have any names incoming on your
16:45geometry um it doesn't matter what the
16:48name of the attribute is that stores the
16:50name but if there is some form of name
16:53coming in you can use that and I will
16:56show you how the easiest way is to use
16:59an attribute
17:02copy and you just
17:05connect both inputs to the
17:07same incoming geometry and what it will
17:11do is it will copy an attribute from the
17:12geometry to itself but you can tell to
17:15give it a new name so I will use the
17:18name attribute I will give it a new name
17:20when I copy it and I will call it
17:22musclecore
17:24ID now this little warning here isn't
17:28too important but I'll just change my
17:30group types to Primitives because my
17:31attributes are primitive attributes so
17:34now if we look at the info we'll see
17:36that the name attribute still exists but
17:38now there is this new attribute and we
17:40know it's new because it's bold here and
17:44it is muscle
17:45ID and in the geometry spreadsheet in
17:47The Primitives tab we can see that these
17:51two match so now we have a muscle ID and
17:55that's perfect we don't need to do
17:56anything else uh if you have a name
18:00that's coming in in a different form
18:01perhaps as a path attribute where you'll
18:04need to do a bit more editing to extract
18:06the name from it I will have a separate
18:08video in the advanced topics to cover
18:10that but I don't want to get uh too
18:12sidetracked now so I will leave that for
18:14separate video but now let's say we're
18:18in a situation where we don't have any
18:21incoming name attribute whatsoever now
18:24this is a situation where we will want
18:26to use a muscle ID node
18:31okay so I'm going to create
18:36it oh I just want to also show sometimes
18:39if you create it and it's not connected
18:43you'll get an
18:44error and the best way to get rid of
18:46that error is just to hit control+ c um
18:49it didn't really happen properly in this
18:50case but sometimes it happens for some
18:52of the other muscle nodes and then it's
18:54useful to know just hit contrl C we'll
18:56get rid of that error it's just a
18:58stashing Arrow
19:00so what we want to do is we want to
19:03enter the viewport state for this node
19:06now all the muscle nodes have viewport
19:10States so to do that you select the node
19:14you move your cursor to the viewport and
19:16you hit enter so now you'll see it this
19:19has come up this is the group selector
19:23um and normally when you're not in a
19:26viewport state that brings it up you can
19:29either bring it up with the nine key or
19:32with the this um button here but seeing
19:36as it's part of the viewport state or
19:39this node will come up by default with
19:42the correct setting so now when you're
19:44in this viewport State you can just
19:46select a
19:47muscle hit enter and this will pop up so
19:52that you can rename it now the only
19:54requirement for naming is that muscles
19:57on the left side need to start with L
19:59underscore and muscles on the right side
20:01need to start with r underscore and the
20:04default is going to assume that it's
20:06uppercase L and uppercase R you can
20:09change it but I will just stick to the
20:11default for Simplicity sake so
20:15lcore
20:17pectoralis
20:19major sternal so I've just abbreviated
20:23this a bit so that in situations where
20:25there's not a lot space to see the name
20:27it isn't cut off
20:29okay so now we see that it's showing up
20:32as pie 15 still but as soon as I move my
20:34mouse it will update so now you can see
20:39the name of this muscle and it's shown
20:42up here you can also select from this
20:46list instead of from the geometry itself
20:49so let's say I want to do this one hit
20:52enter L
20:55pectoralis major this is the close
20:58cicular
21:00part and so on and so forth I can go in
21:03and rename all my L muscles now for
21:06musles that are in the central line that
21:09don't have um corresponding left and
21:12right muscles there is no uh standard
21:16convention that's expected but I like to
21:19use Capital
21:20ccore to make it easier to group later
21:23on if I need to so select that hit C
21:29and now
21:32um these other two Central muscles are
21:35not really proper
21:36muscles but let me quickly talk about
21:39them I'm going
21:41to use control click on the template of
21:45the rest bones so that they
21:48display as properly shaded instead of
21:52um and wireframe worde when they're
21:55templated but basically the idea here is
21:59that we don't want empty
22:02gaps between muscles and Bones where the
22:05muscles can collapse so
22:07this volume here is just there as a
22:11placeholder to stand in for all the
22:15organs and viseral fat that are located
22:19in the belly cavity um as it's a waste
22:23to have it all broken up separately it's
22:26much simpler to just have one um muscle
22:28volume stand in because we're only
22:31really interested in The Superficial
22:34muscles right because those are the ones
22:35right under the skin and so those are
22:38the ones that we will be seeing but
22:41things under those superficial muscles
22:43can be a lot
22:44simpler so I'm just going to call this
22:48one because it doesn't correspond to an
22:50actual name I'm just going to call this
22:53C
22:55belly cavity
22:58and then this one over here it's a bit
23:02of a cheat this trapezius should have
23:05been a bit thicker actually to make up
23:08for more of this volume but again it's
23:10just to fill in some of that volume so
23:12that these muscles don't collapse so
23:13it's just a simplification
23:15of what's normally in this
23:18region and I'll just call it
23:22C neck
23:25filler and now I've named my central
23:28muscle
23:29I
23:30accidentally exited the viewport State
23:32because I'm using a mouse I'm not used
23:35to um but we're back in it now
23:39um and while we're here while I was
23:42talking about these sort of um
23:46standin volume filling muscles I'm also
23:49going to talk about the bone geometry
23:53bit in that you'll notice the rib cage
23:56is a solid mesh instead of individual
23:59rib
23:59bones um and that is just to simplify it
24:03number one the fewer points you have in
24:07your bone Collision mesh the faster your
24:09sim will run because um every point in
24:13your sim is going to look at every other
24:16at every point in the Collision mesh so
24:18the more points are the longer the
24:19Collision detection will take so
24:22simplifying your bones is going to save
24:25a lot of sim time and also the few
24:29High detail cavities and crevices there
24:32are in your bones the less your danger
24:35there is for the muscles to get trapped
24:37in funny holes but if you would like
24:41some of that nice um surface detail of
24:44the ribs you can always use a a volume
24:47like this but with the rib um profile
24:52sculpted
24:54in and you can see in general the other
24:57Bones have been simplified
24:59phont and you could probably even take
25:02it a bit further many people suggest
25:06removing
25:07patellas you probably don't need all
25:09your hand
25:10bones
25:12Etc okay so now let's talk about
25:14symmetry a bit so I mentioned that you
25:17need the convention is to use lore for
25:20your left muscles so you can see here
25:23for each muscle that I named it's
25:25created a new tab if you make a typo you
25:29can go and edit it here afterwards and
25:32that will
25:34update um you can also delete any of
25:37these if you're not happy with them but
25:40let's say we want to mirror our muscles
25:43which we typically will if we only have
25:46one side to begin with so I will create
25:48a muscle mirror
25:50node typically we create this later down
25:54um in the workflow but I'm just going to
25:57put the down now to demonstrate how the
26:00naming Mirror Works
26:03so firstly I'll show a handy little
26:06trick with why I like to um use the
26:10ccore for the central muscles if we
26:13select one of these Central
26:15muscles as I'll group and I'm going to
26:19replace everything after
26:21ccore with an asterisk also known as a
26:24wild card which means
26:27anything match ing the pattern ccore but
26:30now instead of saying equal to we want
26:33it to be everything that's not equal to
26:34this so to do that we put in an
26:36exclamation mark before the equal sign
26:38so now this is saying muscle ID not
26:42equal to
26:44ccore fill in Wild Card pattern so now
26:48if I hit enter you will see it has
26:50mirrored everything except these Central
26:53muscles you'll see what happens is let's
26:56find some muscles that have actually
26:58been
26:59named here so now you can see that it's
27:02gone
27:03from all the lore pectoralis it has now
27:06changed to rore
27:08pectoralis so the muscle mirror will
27:12pick up the prefixing of course if you
27:15had the right side that you're mirroring
27:17you would change it to r underscore and
27:20if it's perhaps it's lowercase r instead
27:22of uppercase R you would do that to if
27:25you wanted
27:26lcore um
27:28you would do it that
27:30way undo whoops but now let's say we
27:35have our left and right muscles there to
27:37begin with so let me just create a
27:39muscle
27:41mirror on the original muscles and now I
27:45don't have anything named so I can't use
27:46the names in the group so instead I'm
27:48just going to have to select them and
27:52control to deselect what I don't
27:56want hit enter
27:59so
28:00now this is mirrored so now if I use a
28:04muscle ID
28:09node and so just to be clear in this
28:12case I've mirrored it but perhaps your
28:14muscles are slightly
28:16asymmetric it will still work with
28:20this so I'm going to select
28:23this and just for Speed sake I'm just
28:25going to make this L Peck and now you'll
28:27see this says alpek this says RPC so it
28:31has
28:31automatically renamed the
28:34corresponding muscle on the other side
28:37um and replace the L with r and you can
28:39see the pink color shows that that
28:40muscle's been renamed and the purple
28:42color shows that that is the
28:45automatically renamed
28:47mirroring muscle so that is how the
28:51muscle ID works with Symmetry and again
28:53if you don't want to use l capital L and
28:57R you can change these or if it's right
28:59or left you can swap
29:01those similarly we want to make sure
29:03that our bones are named and there's no
29:06uh preset for the bone name
29:09attribute but I like to use bone ID if
29:13you
29:14have an attribute already coming in
29:17that's great you can just use it as is
29:19maybe it's a name you can just use it
29:23but let's say you're in a situation
29:25where you don't have any names you can
29:27use the ID node on the bones
29:33too now okay this is the case where the
29:36error isn't going away so I'm just going
29:37to hit contrl C and it will get rid of
29:40it now in theory you can change this to
29:44a different attribute name I did have
29:46some issues with this so I think it's
29:48safer to um
29:51just use
29:53this as muscle ID first and then change
29:56it afterwards so
29:59so I'm just going to type whatever
30:01because I'm not really paying attention
30:03right
30:04now but what you can do is you can do an
30:09attribute
30:11rename you can also do an attribute copy
30:13I'm just showing a different way make
30:15sure you're in the Primitive Tab and now
30:18you're going to go from muscle ID to and
30:22it doesn't matter what this is but I
30:24like to use bone ID uh but I do actually
30:27already have a bone ID attribute so I'm
30:28just going to call it bone ID
30:31new and now you will see that there's
30:34this bold attribute so it's new B ID new
30:38and the muscle ID attribute has gone
30:40away so the difference between the
30:41attribute copy and the attribute rename
30:44is the attribute copy will
30:45keep the name and just duplicate it with
30:48the new
30:50name and the attribute rename will
30:53change the name and thereby removing the
30:56old name
30:58okay so that is how you can create a
31:00bone
31:02ID just delete these because I already
31:05have a bone
31:06ID there is one last thing that we want
31:09to do before we can start properly
31:11setting up our muscles for simulation
31:13and that is to ensure that there are no
31:15intersections between the muscles as
31:18well as between the muscles and the
31:19bones now why don't we want these
31:22intersections strictly speaking Vellum
31:25can handle points that are intersecting
31:27on the first frame of the simulation in
31:29the sense that it doesn't cause them to
31:31explode like something like FM might but
31:35it does this by disabling collisions on
31:38the intersecting points from the first
31:40frame onwards and this can have some
31:42unintended consequences such as if you
31:45have intersections between your muscles
31:47and your bones you can often get gloopy
31:50looking muscles and if you have
31:53intersections between muscles and
31:54muscles that are quite large if the
31:57intersection area is quite large then
31:59I've seen that the muscle to muscle
32:01constraints don't always get created
32:04correctly in that area another thing to
32:07look out for is if you have a quadruped
32:10for instance so it's a bit hard to show
32:12it here but a quadruped will typically
32:15have an a rest position it the back leg
32:18will be quite close to the
32:20abdomen and if you have the leg muscles
32:24penetrating the muscles of the abdomen
32:27then as that leg swings backwards you
32:31can have stretching and pulling of the
32:32muscles if they're penetrating so those
32:34are some of the reasons why we want to
32:37do a check to make sure that our muscles
32:39have no intersections now I will do an
32:41advanced video to show how to actually
32:44fix
32:45intersections but for this video I just
32:47want to show how you can check for them
32:51and you can use that to either kick back
32:53a muscle model to a modeling department
32:56or you can if the problems are small
32:58enough you can maybe fix them with some
33:00small sculpts or
33:02edits and um I recommend the sculpt tool
33:06if you are not familiar with that new
33:08node in 20.5 so for checking I have
33:12created this
33:13subnet it's not a node yet it might
33:17become one in future versions of Houdini
33:20but for now I just left it as a subnet
33:22so that it's very easy to share and if
33:26you want to turn it into an HDA
33:28go ahead so the first input is going to
33:32be the muscles and the second input is
33:33the bones and then you'll see there are
33:35three outputs which I've merged together
33:37just for display reasons the first
33:39output is going to be they're going to
33:41be colored spheres to show where the
33:44intersections are if you don't have any
33:46intersections you won't see anything
33:48second output is going to be muscles
33:49third output will be
33:51bones and so I have already ensured that
33:55this model is clean and without any
33:56intersections
33:58but let's just add some back in so I'll
34:01put down a peak
34:02node and I'm going to set the distance
34:04to
34:0501 and now we see these spheres pop
34:11up so there are three
34:13colors the Orange is for muscle to
34:16muscle
34:17intersections and that is between
34:20separate
34:22muscles you can for all of these you can
34:24change the color you can change the
34:26radius you you can change the intensity
34:29if you want it to Glow more and you can
34:31also change your muscle opacity and your
34:33bone
34:34opacity so these will show where the
34:38muscles are penetrating one another the
34:42next one the muscle self
34:44intersections are showing where there
34:47are um faces or points from one part of
34:51the muscle penetrating another part of
34:53the same muscle so there's this option
34:55here display as points which will
34:58display the Spheres as points
35:01instead just so that when you're zooming
35:03in it's a bit easier to see it's not the
35:06actual geometry isn't completely
35:07obscured by the
35:09Spheres um and this will be useful if
35:11you just wanted to go in and maybe use a
35:15sculpt little smooth to get rid of that
35:19but I will add that the self
35:21intersections aren't as critical to
35:24resolve as the muscle to muscle or
35:26muscle to bone ones are um your muscle
35:30solidifier will often get rid of that
35:32for you basically it will get rid of it
35:34if you aren't doing a remesh separately
35:37beforehand if you just use the remesh
35:39inside the muscle solidify it will fix
35:42any self
35:44intersections but you just need to be
35:45careful because that can change the
35:47shape of the muscle a little bit in that
35:48area so this option is added so that you
35:52can flag it ahead of time and fix it if
35:55you want to have more control over with
35:57the final shape and then lastly there
36:01are the muscle to Bone intersections
36:03I'll turn the spay points off and you
36:06can see them as spheres and I'll also
36:08show here in the info
36:10pane let me turn all of these
36:13on and you can see that each of these
36:17have a corresponding group muscle to
36:19Bone self intersecting muscle to muscle
36:22and you can see that it shows how many
36:26points there are now these points are
36:27just doesn't correspond to points um on
36:31the actual geometry it's points created
36:33by the intersection detection so there
36:36going to be more points typically than
36:38there are intersections but if you have
36:40zero for all of these then you know you
36:43are intersection free and you can
36:45happily continue with setting up your
36:47simulation one final thing I just want
36:50to mention is this is a little bit slow
36:54and because it's doing things like
36:56editing the opacity just for display
36:58reasons um I wouldn't use any of the
37:00output of this for Downstream
37:03calculations in the Sim just keep this
37:05off to the side and carry on working in
37:09your main stream here for any further
37:12steps um you can of course if you had a
37:17situation where you made edits you
37:20can for instance put down a sculpt
37:23node before and the input will update as
37:27you
37:28or you can keep this displayed but
37:31select that and enter the viewport state
37:34for
37:35your
37:36selected sculpt node or whatever I'm
37:39just going to turn off
37:41that and what you can do
37:44now is let's say we want to
37:47fix the Sol intersection here so I will
37:53use smooth maybe reduce the
37:56strength and
37:57and you can see it updates it's not the
38:01fastest it's a bit of a slow update but
38:05it you can um see the results of your
38:08tweaks in real time almost real time so
38:11then once you're happy with that you can
38:13carry
38:15on working Downstream from here and
38:18leave this off to the
38:19side all right in the next video we will
38:23start solidifying the muscles for
38:25simulation

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