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  • Animated mesh objects (Animesh)


    Jeremy Linden

    Getting started with animesh

    Animated mesh (animesh) is a Second Life feature to allow independent objects to use rigged mesh and animations, just as you can with mesh avatars. This means that you can have wild animals, pets, vehicles, scenery features and other objects that play animations.

    Animesh is supported in all regions of the main grid and on the test grid. Currently animesh works with the default viewer. If you need a place to test animesh content, there are some dedicated test regions at Animesh1 and Animesh2, which are set to moderate maturity, and Animesh Adult, which is intended for adult content.

    Sample content animation and mesh files to test creating animesh are available for download at the Second Life Jira: BUG-139234.

    Creating animesh objects

    image.png

    The animesh viewer adds one new feature to the UI for editing an in-world object.

    • Right click a rigged mesh object you have permissions to edit and click Edit
    • Select the Features tab
    • Check Animated Mesh to turn the object into an animesh object

    There are some restrictions: the object must be one you have permissions to modify, it must not exceed the maximum triangle count limit for animesh objects, and you must be in an animesh-enabled region. If any of these condition are not met then the checkbox will not be enabled.

    Note
    Rigged mesh refers to a mesh object created in a 3D modeling program like Blender which has rigging, or data that gives the mesh object a skeleton with joints that can move in specific ways. Without rigging, a mesh object is more like a hollow solid sculpture than a flexible, movable creation.

    Animating animesh objects

    image.png

    Simply setting an object to Animated Mesh doesn't get it moving right away -- it needs an animation file and a script which tells that animation to play.

    • Select your animesh object (Right-click > Edit)
    • Open the Content tab
    • Add your animation and your script to play the animation to the animesh object's contents by dragging them from your Inventory into the Contents box

    Animesh adds three new LSL functions that can be used to run or stop animations, or check which animations are currently running. The commands are:

    For more information on how to use these functions in scripts to use with animesh objects, please click above to visit the Second Life Wiki LSL Portal entry for each one.

    Advanced animesh topics

    Editing animesh position and orientation

    A conventional static mesh object has a position defined when it’s rezzed and an orientation defined when it’s created. An animesh object still has an actual object position in a region, but the displayed mesh is shown at a location determined by its underlying skeleton and currently playing animations. Because of this, the visual location of an animesh object playing an animation may be at some displacement from its "real" position for physics and scripting purposes. Or in simpler terms, the bear object above has a 'fixed' location used for physics and scripts calculations, but its animation may cause it to wiggle around a bit visually. It never actually changes coordinates.

    The skeleton is positioned relative to the original object as follows:

    • The object position is used as the location for the skeleton root joint.
    • The object orientation matches the root object orientation. If the root object is a mesh, the bind shape matrix will be used.
    • Playing animations can alter the visual position and orientation further by animating the pelvis joint.

    One result is that animesh objects will normally be oriented with their local X-axis as the forward direction. Static mesh objects are not necessarily created in this orientation, so there may be a change in orientation when an object becomes animesh. However, if the root object of an animesh linkset is a mesh, the bind shape matrix will also be used. This means that if you want your object to be oriented relative to the static mesh representation, you can use an animesh root mesh. If you want your object to have standard X-forward skeleton orientation, you can use a non-mesh root object (for example, a simple invisible prim) and then align your mesh child objects relative to that.

    Basically, if your static mesh object suddenly faces a different direction when you click Animated Mesh in the Edit window, you may find it helpful to check how the mesh was created originally, or to link your new animesh object to a root object and manipulate it accordingly until it faces the direction you want it to face.

    Using the Edit > Rotation and Edit > Move settings will adjust an animesh object's forward orientation and actual position (coordinates), but Edit > Scale cannot change the animesh object's skeleton, so the object will not visually change size. 

    Position and Scale Constraints

    There are some constraints on the scale and positioning of animesh objects. These are intended to maintain consistency with limits on other types of in-world objects (such as conventional prims), and to make the behavior more predictable.

    • There is a 64m scale limit for animesh objects. Objects exceeding this size threshold will be scaled down so their computed bounding box does not exceed 64m.
    • There is a 3m offset limit for animesh objects. Offset is the distance between the "official" location of the static object and the bounding box of the animesh object as displayed. The display location of animesh objects will be constrained to not exceed this limit.

    These constraints are based on a real-time bounding box maintained for rigged meshes, so they may be triggered at some times and not others depending on the animations being played. For performance reasons the box does not update every frame, so the constraints can lag behind the current appearance slightly.

    Animesh building suggestions

    Animesh objects do not have attachments the way avatars do. To combine multiple meshes in a single animesh, you would link them together into a single linkset. If you link together multiple meshes, the original source meshes and any corresponding physics representations can be scattered around multiple locations. The meshes will all still display rigged to a single skeleton, with orientation as noted above. The recommended practice for now is to have a root prim that’s not a rigged mesh, and associate any physics representation with that root prim. The rigged meshes would then be non-physical children of this root.

    Also note that like rigged meshes on avatars, the rigged meshes in animesh objects are non-physical. The animation process only affects how things display on the viewer, so if you want to have a physics shape that lines up with your animesh object, you will need to manage the positioning and animations accordingly.

    Animesh attachments

    Animesh objects can also be attachments on your avatar. Like a conventional static attachment, an animesh attachment will move with the selected attachment point on your avatar, such as your right shoulder or left hand. Animesh attachments can then run animations, which can change their apparent position relative to their attachment point (for example, if the pelvis joint is part of the animation).

    Like static attachments, animesh attachments can be repositioned using the editing controls. Changing position or rotation will move the attachment relative to its attachment point.

    Currently, you can have at most one animesh attachment at a time as a Basic member or two animesh attachments if you are a Premium or Premium Plus member.

    Animesh Skeleton State and Customization

    Avatars support extensive customization via sliders. The bones in an avatar skeleton are positioned and scaled based on these customization settings, which are stored mostly in the avatar's shape wearable. Animesh objects do not currently support this type of customization; they do not have shape wearables, so there is no way to do the same kind of skeleton customization for them. The bone positions and scales for an animesh object are simply initialized from the default bone settings (defined in some configuration files that are part of the viewer installation - avatar_skeleton.xml and avatar_lad.xml). These default bone positions and scales can be overridden in the uploaded meshes, using values defined when the meshes were created. This is the same joint position mechanism that rigged meshes can also use to customize avatar positioning.

    We know there is a lot of interest in supporting more extensive customization of animesh objects, and are hoping to tackle this in a future project.

    Animesh information and displays

    Some additional displays are available to help you see the state of animesh objects:

    image.png

    In the Advanced menu, the option Performance Tools > Show avatar complexity information shows you the computed complexity cost for avatars. The complexity display only works for avatars and independent animesh objects. Attached animesh objects have their complexity added to the avatar they are attached to, so they are not shown with a complexity display of their own. Show avatar complexity information now works for animesh objects as well and includes additional information as follows:

    • VisTris is the number of currently displayed triangles associated with the object, based on the currently displayed LODs (levels of detail) for its component primitives.
    •  EstMaxTris is an estimated triangle count for the most complex LODs of the object; this is the number used to determine whether an object exceeds the triangle count complexity limit for animesh objects.
    image.png

    Another updated display is Develop > Render Metadata > Collision skeleton. This will show the collision volumes for animesh objects as well as avatars, with the animesh objects shown a different color:

    • The avatar in the example image has a blue skeleton
    • The animesh bear is shown with a red skeleton

    In the same menu, Develop > Render Metadata > Joints will show the regular bones in the skeleton of both avatars and animesh objects.

    Both of the Render Metadata displays have a significant performance impact, so you will probably not want to enable them most of the time.

     

    Animesh FAQ

    What happens if I have an unsupported viewer?

    If you visit an animesh-enabled region with a non-animesh viewer, you will see animesh objects as non-animated static mesh objects, and animesh attachments as rigged meshes on the host avatar.

    What happens if I visit unsupported regions and try to use animesh content?

    This situation should not come up now that animesh support is enabled on the main grid. If you do run into a region, perhaps on the test grid, that lacks animesh support, then animesh objects will not work correctly. Scripts that try to use the new animesh LSL functions will give an error message if run in a non-animesh region. Once you return to an animesh region you may need to reset the script to get it working again.

    How can report a bug or request new features?

    Please report the bug using the standard JIRA process, and include [ANIMESH] in the title.

    How can I engage with other users of animesh?

    • Visit the content creation forum area for animesh: https://community.secondlife.com/forums/forum/354-animesh/. Linden Lab will monitor this area while animesh is under development, and we will try to respond to questions of general interest.
    • Attend the Content Creation User Group meeting, which is held most weeks on Thursday. All are welcome. See the Content Creation User Group Wiki Page for location and schedule information.

    Will any of my pre-animesh content change?

    No. Animesh is a new setting for mesh objects. Any content created without that setting should continue to work the same as before. If you see any change in the behavior of non-animesh objects, please report it as a bug.

    What’s the difference between an animesh attachment and a regular rigged mesh attachment? When should I use one or the other?

    Animesh attachments have a complete skeleton of their own, so they can move completely independently from your avatar. For example, an animesh fairy could flap its own wings separately from the wings on your avatar (this also means that animations between animesh objects and your own avatar may not be completely in sync, since they are animated independently). An animesh attachment can also become an independent object if it is detached. Regular mesh attachments use your avatar’s skeleton, so if they want to animate any part of your avatar they have to cooperate with other attachments. There are some cases where you could use either an animated attachment or a rigged mesh: if the object uses joints that are not being used for anything else, for example, it animates the wing bones of an avatar that does not have wings, then this could be implemented using either a regular rigged mesh attachment or an animesh attachment.

    Are there any restrictions on animesh content?

    The current limits are intended to help manage the performance costs associated with animesh objects:

    • There is a limit to how many animesh objects can be attached to an avatar at one time. Currently this is a maximum of one for Basic members and two for Premium and Premium Plus members.
    • Animesh objects in-world (ie, not attached to an avatar) will have a land impact that counts against the limits for the region they are in.
      • Currently being animesh adds an additional 15 to the land impact of an object to reflect the extra resources these objects utilize.
      • There is an additional land impact cost of 1.5 per 1,000 charged triangles in the model.
        • All triangles in the highest LOD are charged, but only triangles exceeding a limit are charged in the coarser LODs; there is no LI penalty for LODs as long as each does not exceed half the complexity of the next highest level - for example, if the highest LOD has 10,000 triangles, you could make LODs with no penalty up to 5,000 triangles in the medium LOD, 2,500 in the low LOD, and 1,250 in the lowest LOD. LODs that exceed those limits will be counted against the LI only for any excess above those limits.
    • Animesh objects have a complexity limit based on triangle count. Currently an animesh object can have at most 100,000 triangles in its most detailed LOD. This 100,000 limit is based on estimated triangle count, so the actual number of triangles can often be a bit higher.
    • Attached animesh objects, like other attachments, do not count against land impact. However, they do affect the Avatar Rendering Cost calculations for the avatar they are attached to. The ARC for animesh objects, like the ARC for avatars, incorporates the effects of graphics properties of the mesh objects, and is scaled to be roughly proportional to the land impact - for example, if an animesh object has 50% higher land impact than the corresponding static mesh, then the ARC for that animesh should also be roughly 50% higher.
       

    Edited by Maggie Linden
    Premium Plus update




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