[Blender 2.8/2.9 ]Un-confusing the NLA Editor (Nonlinear Animation)

hi everyone this is an intro to the non-linear animation editor or nla in blender i assume that you have a basic understanding of keyframes action curves and so on if you don't watch the previous video the goal of this video is to unconfuse the nla there are just a few concepts in this editor that you need to grasp and that will determine if you have a nice experience working with non-linear animation or a painful one i admit this video won't be cool we'll be using a simple cone object again but that will give us a good foundation and that will enable us to do something more interesting using rigged characters in the next video if you like my stuff and want to support me you can do so on gumroad or patreon okay i'll start with a new scene i'm going to create cone or any other object and organize my scene a bit i'm going to want a timeline action editor and nla and now i'm going to create three very simple actions which will help us explain a lot of what is going on in the nla i want one action where the cone is just moving on the x-axis so i'm going to create a new action and call it move x i want to show the end panel item and now i'm going to insert a new keyframe on frame 1 for location and then move the timeline to frame 50 for example move my cone on the x-axis and insert another location keyframe it is very important to note that even though i'm only moving the cone on the x-axis i'm keying i'm inserting keyframes for all axis you'll see why this is important when we start working with the nla now i'm going to move to frame 1 again create a fake user for this section and unlink it then i'm going to create a new action call it move zed insert a keyframe again at the default position for location and then again move to frame 50 for example move the cone up and insert another location keyframe again we only have movement on one axis but i am keyframing the whole set of location axis now again move to frame one create a fake user unlink and create another action and i'm going to call this one just rotate on frame one i'm going to insert one rotation keyframe by pressing i and then go to frame 50 for example and i want my object to rotate 360 degrees on the y-axis i can do that manually in the viewport but it's actually easier to just insert 360 here on the for the y-axis and then while my mouse is here i'm going to press i and that will create a new keyframe now let's start moving these actions to the nla i'm going to set fake user for this action and then switch to move x if i expand the data for the cone here you'll see that we have animation data and under it is the move x action as the current action now i'm going to press the push down button to move this action to the nla and notice how it was automatically unlinked which also made it disappear from the animation data and instead we got a new nla track you're probably not going to view this object data often but it is useful to be aware of it among other things it is showing you what animation data is driving your object so now i'm going to set moveset as the active action now we have an active action under animation and an nla track having this combination of an active action and nla is actually one of the more confusing situations that you can have while working with the nla i'm going to try to explain how to deal with this in this video but for now i'm just going to push down this action down to the nla as well and then again i'm going to set the active action to rotate and push it down as well now we have a very simple nla setup but this will allow us to explain and understand some of the most important and confusing parts of this editor first let's define some terms on the right in the nla editor we have what is called tracks tracks are similar to photoshop layers it is not a perfect analogy but just like photoshop layers tracks are stacked from bottom to top so the tracks further up are modifying the tracks below them actions once they are pushed down to the nla become these rectangular strips those are called action strips i may get sloppy with the naming and call them either strips or actions or even animations also instead of tracks i may say layers but i think it will be clear what i'm talking about ok let's look at the tracks first there are a few things that we can do with them i can rename them by double clicking on them this is entirely for organizational purposes the name should explain what kind of actions or what kind of effect you're trying to achieve with this layer or truck in this case we have just one action strip on each track so let's name the tracks the same as the layers this one will be move x move zed and rotate now if i scrub through this action here that we have in the nla you'll see that the cone goes up while rotating this is the result of the current combination of actions that we have here my goal with this video will be to explain why this is the result you see and how to change this behavior and then we'll be able to easily apply this same approach to more complex scenes but anyway back to the tracks each of them has this checkbox if i uncheck the rotate the cone will no longer rotate it will just go up that is because the rotation action was now disabled this checkbox disables all strips on this truck in this case i only have one action on this truck but if i had more then all of them would have been disabled notice how the rotation strip was surrounded by a dotted line this in the nla means that the action is not being evaluated that it is disabled i wish the visual cue was more obvious but it is what it is so dotted line means disabled if i disable new move set track for example then the lowest track the move x track will become visible and we'll be able to play this movement on the x-axis and now if i tick back the rotate track then i'll have movement on the x-axis while the cone is spinning one thing to note is that if i go to the middle of the action and then untick the rotate track and then scrub through the timeline you'll notice that the cone stays in this rotated state and the reason for that is really not that complicated but if you don't take the time to understand it it will confuse the hell out of you when working on more complex scenes i'll do my best to explain this behavior but let's activate back all of the tracks and then look at this lock icon that we have as well locking a truck will prevent you from doing any changes to this track so if i lock the move set track i'll no longer be able to move this strip that i have on it you know the other strips i can just drag with the mouse and move but this one i can't also if this was unlocked i can move a track and drag it on this upper track but if i undo and lock this track then i'm no longer able to move this track onto the locked track and this can be useful when you want to avoid accidental changes to a certain track in your nla i'm going to unlock all and finally let's look at this star icon here the star simply makes one of the tracks the only active animation for this object if i start the move extract then i'll only have the movement on the x-axis if i start the move z track my object will only move on the z-axis and if i study rotate it will only rotate so starring is similar to if i install it here and then uncheck all tracks except for one then we'll have something similar but if i had many tracks here that could be very tedious and so i can do it with just one click by clicking the star icon i see this feature as a way to preview one of the tracks independently from all others at least that's how i use it so for my final animation i'll want to remove any stars and just have all my tracks in unstarred mode i'm going to tick all actions again let's move to the next important topic which is blending and mixing actions as you probably understand mixing actions is one of the main strengths of this nla system in a simple example we are already mixing the location and rotation actions so the cone is moving up and rotating which is a mix of the move set and rotate actions that we created earlier if i disable the move that track then again the cone will be moving sideways and spinning but the two movement action x and z don't seem to be mixing so let's try to figure out what's going on for this purpose we'll introduce another feature of the nla which is blending modes i'll uncheck the rotation track and select the move z action strip and then i'll expand this side panel which is similar to the end panel in the 3d view the shortcut for it is again n and let's move to the strip tab we'll ignore the other two tabs and i'll talk about them later in this tab you'll see options for the active strip for the strip that we have selected here you'll see the name of the strip that you're editing at the top and now we're going to focus on this blending option by default it is set to replace but we have a few other options to choose from like combine add subtract and multiply and here we can return to a photoshop layer analogy in photoshop if i have a layer filled with red color and then i create a new layer and fill it with green then the upper layer will completely cover the lower one and then we have blending modes like multiply add subtract etc nla action blending is similar except that we are not blending rgb values but whatever properties are keyframed in the actions the default option replace is like the default blending mode in photoshop it completely covers any values below it unless we reduce the opacity that is something that we can do in the nla as well but i'll talk about it later so that is why when we have these two strips one over the other the upper one overrides the lower one since both have location x y zed keyframes whichever strips is above will completely replace the lower one and this mixing of values is being evaluated on every frame as we go through the timeline so on frame one we have something like this and then if you move to frame 25 for example we'll have values like this as you can see the first action has some sort of value for the x movement but it is being replaced by the value set in the upper action and that value is zero constantly throughout the whole action and so the final value for the x movement of this object of this cone is constantly zero and that is why the cone is only moving up and not sideways if i now switch the blending mode to add and preview my action you'll see that the cone is moving diagonally so the x and z movements were now combined if we look at my improvised graph again this is what is happening on frame 1 we have the object in the initial position because both actions that we are mixing are set to 0 0 0 at this point of time if we move forward in time at any frame for example 20 we'll see that the xyz values of each strip are being added together and that allows the x value to show through and that is how we get this mixing of the movement the add blending mode is one of the most commonly used ones in the nla and you'll be using it a lot when mixing animations another blending mode that we have is subtract this mode instead of adding the values together it will subtract any value of move z from move x and that gives us this inverted movement in the z-axis you can kind of think of this mode as inverting any value that the strip holds we also have multiply can you guess what will happen if i set the blending mode to multiply the object will stay completely still because each action has a value that is a constant zero throughout this action and anything multiplied by zero is zero so all x y z values are zeroed out throughout the whole animation and finally there is combine this mode is similar to the add mode but instead of simple addition of the values it uses more complex formulas that also depend on what is being blended so it will use one formula for location values another for rotation and a different one for scale and so on so most of the time you'll be using either add or replace but of course you can experiment with the other modes and find special uses for them okay let's set move that to add and activate rotation and now we'll have this diagonal movement while the the cone is also spinning however if i select the rotate strip you'll see that blending is still set to replace so why isn't it overriding the previous actions that is very simple actually it is because the rotate action does not have any location keyframes it only has rotation ones and so the calculation simply passes through this action and makes it into the final result similarly because move x and that do not have any rotation keyframes the calculation simply passes through these actions it finds the rotation keyframes in the rotate strip and then that becomes the final result now if i set the rotate action as the active action in the action editor and just add one location keyframe for it and then just unlink the action this edit will be reflected in the action strip because the action strip simply holds an instance of the action and now if i scrub through the timeline the cone will be just spinning in place and that is because we now have a location keyframe in the rotate action and since blending is set to replace it is overriding anything below it one thing that can kind of confuse you is we only added a single location keyframe at frame one so why is it overriding the entire length of the other actions that is easy to see in the graph editor so i'll reorganize my layout a little bit and switch to graph editor here actually before that i should activate my action in the dope sheet action editor activate rotate and then switch to graph editor and i'll hide my rotation keyframes and just focus on the on the location once and you'll see that even though we just have a single keyframe it produces this line that extends in either direction into infinity if i create another location keyframe here on another frame you'll see that the last keyframe always extends into infinity in the positive direction and the first k frame always extends into infinity in the negative direction and that is why a single location keyframe made such a difference in the nla and when mixing actions in the nla you should always be aware of what is being mixed in your action strips now i don't need these location keyframes so i'm just going to clear them by right clicking here and choosing clear keyframes and i'll switch back to the dope sheet and action editor one more option that can cause confusion is extrapolation let's unlink the rotate action and disable the rotate track and the z strip i'm going to set to replace again so now we just have a up and down movement and let's drag the x movement strip and place it next to the move z1 now if i scrub through this timeline i'll have the cone going up and then as soon as i reach move x it will switch to the move x action okay i think that is intuitive to understand now if i simply move the move x action on the track below it but i'll keep the general timing then let's see what happens i'll scrub again through the move z action and as we expect it moves up but then when we reach the move x section nothing happens so why is that there is nothing about the x movement so it should play right but this is because of the strip extrapolation options if i select move zed and look under extrapolation you'll see that it is set to hold hold means that the pose at the beginning of a strip will extend back into infinity and the end will extend forward in time into infinity this is similar to what we just saw with curves and keyframes and the way the first and the last one kinda extended back and forth in time but unlike curves this behavior can be turned off for the strips in the nla and we do that using the extrapolation options before we change it notice the brownish color that extends in both directions from the move zed action strip let's change extrapolation to hold forward and you'll see that the brownish color disappeared from behind this action strip we don't have anything behind the strip so the effect of it is kind of hard to see so so let's select the final option which is nothing and you'll see that the brownish color disappeared from the end of the action strip now if i play through this action i have the movement up of the cone then as i go in the space between these two actions my cone will kind of weirdly jump to its default position and then as i move into the move x strip we'll see the move x action so this is extrapolation if defines whether an action strip holds its initial and last pose but notice again how after we go past the moveset action the cone jumps to a default position and that is one of the main reasons why we want this kind of extrapolation you generally want your object to stay in place after an action is over instead of jumping to some sort of arbitrary default position okay let's return this strip to its initial position and then we'll move to the next topic something else that can be confusing is having strips in the nla which creates some sort of animation and then adding a new active action so a combination between nla and an active action let's give it a try i'm going to create a new action here by clicking new and this new action is automatically placed in the nla as a special kind of track it is special because it is always on the top of the stack and also it doesn't contain any strips it just contains the action the keyframes that are being edited in the action editor but other than that it behaves the same as other tracks if i click on this track i'll see the options for it and as you can see it also has extrapolation and blending options another way to see these options is if i select any of the strips and then move to the edited action tab i'll see the exact same options now i still don't have any keyframes in this new action that i created so if i scrub through the timeline i'll see the exact action that i have created in the nla let's set this strip to add and activate rotate so we have something more interesting and now we have the cone moving diagonally and spinning if i go to frame one and set one location keyframe for my new action then that will override the movement in the nla clip and the comb will just spin in place that is because blending is set to replace and we just added a new location keyframe and that is overriding any movement that is on the tracks below it if i go to frame 20 and move the cone a little bit and record another location keyframe then we'll have this new movement and at the same time the cone is rotating this is because we have no rotation keyframes here and so the rotation keyframes from the track below are coming through if i set the extrapolation for this new action to nothing then as soon as i go past the last keyframe of this action then i'll see the result from the strips below the new action since we took the time to understand how blending and extrapolation works this shouldn't be hard to understand all right we are kind of done with the really difficult stuff the star icon blending modes extrapolation and having an active action over the nla these are the things that have a high chance to confuse you in the nla i hope this presentation so far helps you out in these areas the rest of the features should be easier to understand i'll start going through the other options in the side panel so i'm going to unlink this new action and remove it from my animation data and i'll select any of the strips and i'll start going through the other options in the end panel from top to bottom but i'll probably have to jump around the options to explain different related settings at the top of the end panel you'll see a text field it contains the name of the active strip if i rename it here you'll see the name update on the strip itself let's undo this name change one thing that can cause uncertainty is if i expand action clip you'll see another text field which has the same name in it this here is actually the name of the action that we created at the beginning of this video and that is attached to this strip here when we pushed down the action from the action editor to the nla blender automatically gave the strip the same name as the action that it uses so that's why we have the same names here but the name of the strip i can change at any point it is just for organizational purposes the action field on the other hand shows which of the existing actions will be played for this action strip i can actually click here and select one of the other actions usually you wouldn't change the associated action in this way but if you wanted to you can in this case i won't and i'll also undo the name change next to the strip name there is a checkbox if i click it that will mute this action strip or disable it and it won't be evaluated in the nla anymore notice how this action strip got a dotted line around it just like when we disable a whole truck so basically the same thing is happening the only difference is that if we disable an individual strip only this strip will be disabled whereas disabling the whole track will disable any other strips that may be on the track if i move the movex track here you'll see that it automatically becomes becomes disabled because the whole track is disabled by the way the shortcut for disabling a strip is h which is the same shortcut as hiding something in the 3d viewport okay next something very useful that you can do in the nla is to change the timing of a whole action so you can make it faster or slower as a whole very easily and non-destructively meaning that the original action will not be changed only the action strip in the nla will be changed doing this is actually quite simple but there are a couple of settings here in the end panel related to timing and explaining how they are related can get a little bit confusing but one of the easiest way to scale an action is to use the playback scale setting if i scale it up this whole action strip will become much longer and so the action will take much longer to play through let's actually start this track to only see this action and you'll see that the z movement is taking quite a bit longer than the initial 50 frames that we had i can also scale it down and make it faster this way of editing always keeps the beginning of the clip and it tweaks the end of it another way to retime this action strip is to use the frame start and frame and options if i move the frame end this action will again become longer and thus slower and i can also move the frame start and that will affect where this action starts and this gives us very precise control over the beginning and end of an action another easy way to scale an action is using the s shortcut so if i just press s this action will be scaled the scaling of the action is defined by the timeline so if i have the timeline in the middle it will scale in both directions if i place it at the beginning of the action it will scale away from it i'll set the frame start and end again to 1 and 50. by the way with the s shortcut i can select multiple strips and scale them at the same time it is important not to confuse the frame start and end under active strip with the very similar settings under action clip i'll explain the difference in a bit by the way notice how when i tweak the frame end the playback scale is also being affected simultaneously however when i tweak the start the scale is not affected and i think that is a bug it should be affected just keep that in mind before we move on i want to introduce an important feature of the nla that will also help us better understand the next points and that is edit mode for action strips as you know in the 3d view we can press tab and go to edit mode and here we can tweak the vertices and polygons of this object let's remove the star and now in the nla if i select a strip and press tab i'll enter a somewhat similar edit mode for action strips what happens when i press tab is blender automatically sets the action attached to this action strip is the active action here in the action editor and now i can edit it i can move keyframes i can add new ones if i wanted to and now if i go back to the nla and press tab again i'll be back to the previous state so the active action will be unlinked and everything will be back to the previous state of course i can set my active action manually here and edit it but then once i am done editing i'll have to manually unlink it and and so on so this is just a much faster way to edit an action just select it in the nla press tab and edit away another advantage of this method is that if i scale this action or move it the keyframes will stick to it and if i want to see the unedited action i can simply click this pin icon here and that will display the actual keyframes of the action without the retiming of the action strip and that can be useful because when you edit a scaled action you can end up with keyframes which are on sub frames so instead of frame 9 your keyframe may be on 9.35 and you may not want that that is a complex topic and you'll need some practice to get used to it but i hope this explanation gives you a basic understanding of this feature and by the way if you press shift tab instead of just tap you will again enter edit mode but your track will also be automatically start and that will allow you to just work on your single action without the other strips interfering and with shift and tap again you'll go back to unstart mode and now let's look at this second pair of frame start and frame and settings if i tweak these settings the strip will again become longer or shorter so very similar to what happens with the other settings above but what really happens is completely different this is actually very easy to see in edit mode if i go to edit mode you'll see that even though my action strip appears longer the keyframes or the timing was not actually edited let's set this to 50 again and if i tweak these settings the keyframes will be changed proportionally to the size of the strip whereas changing this setting will simply make the strip longer or shorter without affecting the keyframes this allows us to cut parts of the actions if i don't want the end of the section i can cut it out and on the opposite side we can create this padding at the end of the action which is mostly useless more often you'll want to cut the end of your action and there is one very practical scenario where this is useful and that is when you have a looping animation like a walk cycle in which the first and the last frames are basically the same and when you repeat this action you get a little hiccup right where the action repeats so what you can do is if your original action is 50 frames you can set this end setting to 49 and that will remove that last keyframe and it will make your looping action smoother now let's cut this action and then go out of edit mode by pressing tab and the length of the strip will jump to the actual length of the action and that is because this sync length option is on if i uncheck it and then go to edit mode and then edit the end parameter and go out of edit mode then the length of the strip won't be changed but if i want to manually sync the length of the strip and the actual action i can press this now button and that will make my strip exactly as long as the actual action speaking of looping the nla has a feature that lets you quickly repeat any action as many times as you want it is called repeat and it is right here at the bottom of the end panel the default value is one which means that the whole action will play exactly once but if i change it to 2 for example we have a repeating action let's start move that to see it more clearly we have the cone moving up and then jumping down and moving up again this feature is more useful for repeating actions so let's start the rotate action select it give it let's say four repetitions and we'll have the cone spinning four times now this doesn't have to be a whole value it could be 3.5 for example so we'll have the cone spin three times fully and then spin halfway the fourth time and stop another option in the end panel that will be easy to understand is reversed i'm going to unstart the rotate action and let's start the moveset action instead and now if i select this strip and enable the reversed option here the action will play backwards so this checkbox effectively flips all keyframes of the entire action and makes it play in reverse it's probably not something that you'll use all the time but when you do need it it's nice to be able to invert an entire animation with the click of a button the checkbox that we have below it cyclic strip time i actually don't understand i tried to figure it out for this video but i couldn't blender's manual explains this checkbox as follows cycle the animated time within the action start and end and if anyone can tell me what that means i'd be very grateful i couldn't get this setting to do anything at all and the final topic that we should cover when it comes to the nla is influence the settings that are related to influence are blend in blend out and this animated influence checkbox if we go back to the photoshop analogy one last time influence is similar to the opacity of photoshop layers one of the most common ways in which you'll be using this feature is through the blend in and blend out settings blend in will create some blending at the beginning of the action and blend out will create blending at the end of the action when we edit values for the these settings you will see that there is a sloped line that appears at the end of the strip it's actually a little bit hard to see when we have this strip selected so if i just click somewhere in the interface you may be able to see it better this will help you blend different action strips so that they don't start or end suddenly and instead they flow smoothly one after the other or one into the other now this simple scene here served us very well in explaining most of the settings until now but when it comes to creating smooth transitions between actions i struggled to create a meaningful example with this cone the influence in blending makes much more sense in a more complex examples like when working with the rigged character so let's leave the detailed explanations for the next video where we'll be working with an actual character the animated influence checkbox will allow you to control the blending and influence with an action curve and that gives you full control over the amount of influence that this strip will have throughout the action the animated strip time feature is actually quite similar it allows you to control the speed of the action similar to the playback scale however again you're able to use an action curve which gives you even more control i'll try to cover these and other advanced features in the next video let's go back to something that i said much earlier in this video if i unstart this action and let's disable the blending and disable reversed now if i go somewhere in the middle of the section and disable the rotate track the cone will just stay in this rotated state but the movement actions will be performed as usual this is because by disabling the rotate action i removed all existing rotation keyframes this is something i also mentioned in the previous video but when there are no keyframes for a certain transformation channel like rotation then the object will simply keep the current values that you see on the transform i can tweak these orientation values any way i want and the comb will just stay in whatever rotated state i leave it in and this can be very confusing when working on a more complex scene one scenario where this confused me a lot was when creating character animations i would have some actions with the arms in fk mode and others in ik mode but i'd forget to keyframe the ik fk switch and that would just mess up my animations so i think one of the main lessons that you should take away from this video is to always be aware of the kind of properties that are keyframed in each action in the nla because that will affect the way these actions are blended together alright before we wrap things up let's look at the differences between these push down and stash buttons that we have in the action editor both of these buttons will move the active action to the nla however there are some differences let's quickly create a random action i'll click the new button and disable all of my nla track tracks so that they don't get in the way and i'll clear my transforms and i'll create one frame here and just another one randomly we already gained some experience with the push down button it will move the new action from the action editor to the top of the nla stack and the new track will be active and your strip will be ready to use let's undo this and press stash instead the action will now appear at the bottom of the nla stack and the new truck was automatically disabled and locked other than that it's a normal truck i can enable it and unlock it at any time and it will be like any other truck you can use stashing instead of blenders unintuitive fake user in the previous video i mentioned that if an action is not active on any object and it is not tagged with this fake user this shield icon here then it will be deleted the next time you save close and reopen your scene but if you stash your action it becomes part of the nla and blender won't delete it if we look under the list of actions here you'll see that the new action that i created is not marked with a zero that is because it is used down here in the nla and that's it for this video i hope it will help you use the nla and not be confused by it tune in next time when we'll do something more fun we'll work on an animated character and create a little animation for it by blending a bunch of separate actions in the nla thank you to everyone who is supporting me by watching my videos and special thanks to my gumroad and patreon supporters you rock and help me out a lot please click like and subscribe and talk to you next time

Channel: CGDive

Views: 22,462

Keywords:

Id: tAo7HxxxA08

Length: 40min 30sec (2430 seconds)

Published: Sat Mar 27 2021

Reddit Comments

[u/justamundane00]

Any tip on modifying influence per strip?

[u/neznein9]

Thank you, needed to see this.