Modeling Geometries

Geometric parts are modeled to be used in IG.Creator and enrich the structure and visualize the product. The reuse of the same is very important to minimize the amount of data on the server-side, transfer side, and client-side.

For checking the basic requirements, this checklist can be used. hinweise_3d_objekte.pdf

• Make sure to clone the respective directory of the respective project from git.ig.
• The required information for modeling geometries of a new project or an existing project can be found in the index.txt file, placed into the geometries folder.

• As a general rule the origin should be set at the Left Low Back corner of the geometry.
• Exceptions can be made in special cases e.g. for geometries that are required to rotate around a specific pivot point.
• Before exporting check for any transformations that may still need to be applied to the geometry.

• The required dimensions of all the geometries to be modeled are provided, So make sure the dimensions are the same as required.
• Make sure the dimensions are correct, at times the dimensions are provided in cm, while Blender by default takes the values in m. Do not forget to convert the values to m.
• Components can be parameterized by positioning, twisting, scaling, extruding.
• Make sure to set the scale factor to 1 for all and remove any unnecessary rotations.

• The process you use to put together your 3D model determines a lot - how easy it is to edit later, how good it looks when lighting and shaders are applied, how easy it is to deform while animating, and much more.
• While modeling, please keep the mesh topology(edges distributed along the surface of an object) clean and simple to avoid shading and vertices doubling.
• Afterwards, which can also be modified or animated if needed.

The Standard size (used for the mobile and web applications) for the standard.obj is as follows:

• Large objects (e.g. whole bed frames, whole bed headboards) ≤ 500 KB
• Medium parts (e.g. armrests, seat cushions) ≤ 200 KB
• Small parts (e.g. handles, bed fuzz) ≤ 50 KB

The size could also be adjusted according to the shape and details of the object.

For high resoluton geometries, please make sure, the file size is not bigger than 5MB for an obj file.

• Unless otherwise needed, the size of the highres geos should not exceed 5MB.
• Leg parts do not need to have highres.

• The UV mapping should be done in a proper way so that the texture material gets wrapped onto the object without breaking the material pattern.
• You can assign a test material like this to the object in blender to check the material mapping.

Unless otherwise specified, the patch size for texture mappings should be 0.15 x 0.15 (15 cm x 15 cm).

• Wood recommended patch size 0.50 x 0.50 (50cm x 50cm).
• Delta maps velvet 1.50 x 1.50 (150cm x 150cm)

• The normal maps should be generated with the details as provided in the source visuals. The size should be kept moderate as per the requirement of the details. A good size for baking is 2048×2048. After baking this can be lowered to 1024×1024
• In order for a normalmap to work the target geometry needs a dedicated UV Map for the normals, otherwise the geometry will turn black as seen in the top left corner of the image.
• For more details please have a look into normal map

• For modeling a mesh you can have a look into the source visuals for a better understanding of the object shape and visual perception.
• You can also import the reference picture to Blender as a plane and compare it with your modeled geometry by examining it from multiple angles of view.
• Check the dimensions.
• Have a brief look at the designed models before uploading.

Use the ig explorer to check the geometries. Here you can display static geometries (obj,ctm) as well as animated models or parts with deformation by dragging and dropping them into the environment. https://explorer.intelligentgraphics.biz/ Initially, the geometry is displayed in a dimension texture. It can be helpful to change the material in order to recognise artefacts. To do this, the expression /?texture=blue or /?texture=leather can be appended to the url to display the material of the geometry in blue or in white leather.

Always test the designed models, whether they look as required, before uploading to IG.Creator

This section is meant to give you a basic outline of how to model a geometry.

• Start off with a basic cube. Set the cubes' dimensions to the dimensions given for your object in the reference sheet. Apply the scale.

• Add a Subdivision Surface Modifier to your cube. Set the 'Levels Viewport' to your liking.

• Add loopcuts and move them until you get an organic shape that resembles the object you intend to model

• Apply the Subdivision Surface Modifier and start reducing the mesh. Select unnecessary Edges and dissolve them by clicking X → Dissolve Edges. Do this until your mesh is simplified enough but keeps its shape. Keep the maximum file size in mind while doing so.

Hint If your mesh is symmetrical you can delete parts of it and use a Mirror Modifier to reduce your workload.

• Further add in details such as stitches. Keep checking the dimensions while editing the mesh to ensure the important measurements are still correct once you're finished. Slight differences due to natural folds, curvatures etc. are to be expected.

• Set Seams for UV Unwrapping. Think about the fabric pattern the real object would use. Refer to stitches you might have modeled as guidelines. Select the loops/ vertices and set them as seam with Edge → 'Mark Seam'
• Sometimes using only existing modeled stitches is not enough and creates undesirable UVs and require additional seams to ensure a clean UV. In this case, seams were added at the bottom. While adding extra seams, keep in mind if they would be visible and disrupt the texture pattern once it's applied.

• Select the entire mesh with 'A' and Unwrap with UV→ Unwrap. Make sure that your Unwrap Method is set to 'Conformal'. Rotate the UV as needed, keep in mind the textures which will be used on the object. Some textures require a specific UV orientation. Scale with the help of UV Magic https://wiki.intelligentgraphics.biz/doku.php?id=ig.guidelines:modelling_geometries#uv_magic
• Move the geometry to the desired origin, usually the lower left back corner. Apply all transforms.

Note: only tested on Windows, shortcuts might differ on iOS

• 'Proportional Editing' can be enabled with shortcut 'O'. It is helpful for organic shaping and modelling. You can adjust the influence with mousewheel up / down.

• Ctrl + E opens the Edge menu, which gives quick acces to 'Mark Seam' and 'Clear Seam'
• Shift + Alt followed by clicking on edge/vertex/face will select the entire loop.
• Clicking x, y or z after a transform action will bind changes to the corresponding axis. e.g. G+X will restrict movement to the X axis.
• U will open the UV menu which gives quick access to 'Unwrap' and options used for UVMagic

• Before setting up an armature, think about how your object will move and how your topology could affect the movement.
• In this example, the armrest had very limited loops in the area where it's supposed to bend; therefore additional loops were added to get more control of the movement. If you notice fewer or more vertices are needed for a clean deformation, you can still remove and add along the way.
• While doing so, keep the file size in mind.

• In Object Mode press shift + A or click 'Add' → 'Armature' to add an armature to your scene.
• Head into the Data Properties of the Armature; under 'Viewport Display' enable 'Names' and 'In Front'. While this is not strictly necessary it will make editing and navigating more clear.
• With your armature selected go into Edit Mode and select the initial bone. Scale and position the bone as needed .
• Select the tip of the bone and press 'E' to extrude it.
• Repeat this step with each new bone until you reach the end of your geometry. While extruding think about where movement will happen and which areas are important to control precisely. Keep this in mind while placing the bones. Tips and roots of the bones should align with the axis of rotation and the edge loops. This can prevent faces from distorting and causing shading artifcats.
• Hint: To constrain actions to an axis press X Y or Z after pressing the action shortcut ( e.g. G followed by Z to move along the Z axis).

• Once your're happy with the bone setup, select your Mesh and head into Edit Mode.
• In the Object Data Properties create a new Vertex Group for each bone.
• The names should be exactly that of the bones. To rename the group simply double click on the name.
• Select the vertices that are to be controlled by their respective bone and click assign while the corresponding Vertex Group is selected.
• You can check the assigned groups by heading into Weight Paint Mode. Click through the groups to see which parts of the mesh are assigned to them. Adjust in Edit Mode if necessary.
• Add an Armature Modifier to your Mesh and select your Armature as Object.

• Note: In rare cases with very simple topology and armature setup it is possible to skip this step entirely: Select the Mesh followed by the Armature and press control + P . Set the Parent to Armature with automatic weights.
• However this is not the recommended workflow as the automatic weights are often not as precise as needed .

• On the Timeline set the End Frame to 100 if not explicitly needed otherwise. Move the Timeline Cursor to frame 0.

• Select the armature and go to Pose Mode.
• Press 'A' to select all bones and 'I' to insert a Keyframe. Choose which transformations you want to key based on the type of deformation you have in mind.
• Move the cursor to frame 100.
• Pose the bones however you want your end position to be. Once you're finished press 'A' followed by 'I' to insert the keyframes.
• If your animation has multiple stages such as a resting position you can also set further keyframes at different frames. Just make sure the final position stays at frame 100.
• Hint: You can reset the bone positions by clicking 'Pose' → 'Clear Transform' → 'All'

• Select your armature followed by the mesh and click export glb. The order is important since it determines the active object.
• In the export properties unfold 'Include' and set a check on 'Selected Objects'.
• Export the glb.

This section will give you a basic overview of how to create a simple mechanical animation of a footrest unfolding from the bottom of a seatcushion.

• Start by modeling out your mechanics.If you do not have any precise measurements it might be easier, so start out modeling the mechanics in its final position to ensure everything fits into place.

• Keep the shapes as simple as possible and ignore details such as screws or holes if not stated otherwise.
• Add your armature. Each bone controlling one part of the mechanical parts. While creating the bones, make sure that the heads/ tails of the bones align with the pivot point of your mechanical parts.
• If you are unsure of where the pivot point is, select the vertices around the area where you intend to set the point, click Shift + S and select 'Cursor to Selected'. The cursor is now at the exact center of your selection. If you selected correctly, this should be your pivot point.

• To set the position of a bone head/ tail to the newly set cursor, select your armature and head into Edit Mode. Select the head/ tail you want to adjust, again click Shift + S, choose Selection to Cursor.

• If you have any separate meshes that are part of the animation and should follow the movement of your mechanics, such as the Cushion in this example, it is not necessary to create a separate animation. To 'copy' the movements of the armature, add a 'Child of' constraint and choose the armature as target and the specific bone whose movement it should follow. You might have to click 'Set Inverse' if the position gets distorted by adding the constraint.
• In this example, the cushion will now follow the movements of Bone.003

If you have modeled your mechanics in its final position, you need to adjust the rest position of the armature and mesh as the animation should start in its 'folded' state.

• With your armature, pose your mechanics to your desired start position.
• Apply the armature modifier to the mechanics.
• Apply the 'Child of' Constraint to the Cushion, apply transforms as necessary. It should have the same position and transforms as the mechanics it is attached to.
• Select your armature. In Pose Mode, Click 'Pose' → 'Apply' → 'Pose as rest Pose'

• Add the armature modifier back to the mechanics mesh.
• Do the same with the 'Child of' modifier for the cushion.
• To simplify the process of creating the mechanical movement, you can use the help of Inverse Kinematics (IK). It allows you to use one bone to affect multiple bones in a chain which will follow it's movement. This saves you the work of having to move and adjust every bone on its own. While the IK Bone will affect every bone in its chain length, individual posing is still possible for the bones and allows you to fine tune and adjust the animation as you wish.
• To add Inverse Kinematics, head into pose mode and select the bone you want to use to control the chain. Head into the Bone Constraint Properties or press Shift + I.
• Select the chain length depending on how many bones should follow your IK Bone. If you leave it at 0, it will automatically assume to use the entire chain.
• For more details on Blenders IK see: https://docs.blender.org/manual/en/latest/animation/armatures/posing/bone_constraints/inverse_kinematics/introduction.html

• Start keying your animation as usual.
• Note: To Export the Cushion with the animation resulting from the 'Child of' modifier, set the glb Animation mode to 'Scene'.

The Tail of the constrained bone will rotate around a set Axis (Track Axis) to point towards a Target. For example this can be used to make a part of the mechanics point to another. https://docs.blender.org/manual/en/latest/animation/constraints/tracking/locked_track.html#index-0

The Tail of the constrained bone will follow a targed using the smallest rotation necessary https://docs.blender.org/manual/en/latest/animation/constraints/tracking/damped_track.html In this example Damped Track was used to control a triangular connection piece (triangle_1) so that it would follow the movement of the main mechanical arm which is controlled by a bone calles 3 IK Control. The constraint ensures that during the animation the triangle is connected to the main arm and doesn't have any offset movements.

Restricts the movement of the constrained bone to a curve. https://docs.blender.org/manual/en/latest/animation/constraints/tracking/clamp_to.html In this case it was used to create a smooth movement and to define the point at wich the control bone moves upwards.

As their name suggests Shape Keys are used key the shape of an object i.e. saved object shapes. More precisely: a Shape Key stores all vertex positions at a specific point in time. They are a helpful tool to create organic animations that blend into each other but also to store the shape caused by modifiers for later use.

• Head into the Object Data Properties and unfold the Shape Keys menu. Click + to add a new Shape Key.
• This is the Basis Shape key, it stores the default shape of your mesh. Any changes done to the Basis key will also be applied to other Shape Keys.

• Click + again to create another Shape Key.
• Select the second Key and Head into Edit Mode to edit your mesh to your desired final shape.

• Go to the Animation tab. Change the mode to Shape Key Editor.

• You should now see your second Key in the Summary.
• Set the key's value to 0 at frame 0. Set it to 1 at frame 100.
• This will create an animation that morphs your default shape into your second key from frame 0 to 100 . Blender will automatically calculate the vertex positions in the frames inbetween , resulting in a smooth organic movement.

• You can use multiple Shape Keys together and also combine Shape Keys with other animation tools such as armatures to create details eg. folds .

• Create a lattice of roughly the same size of the mesh you want to deform. Do not apply any of the transforms to the Lattice.
• Adjust the resolution to your needs. In this case, there will be no changes on the X-Axis therefore Resolution U is set to 1.

• Add a Lattice Modifier to your mesh.
• To your lattice add two Shape Keys. Set the Value of the Second Key to 1 and head into Edit Mode.
• Edit your lattice to your desired deformation.

• Head to the Animation tab. Switch your Mode from Dope Sheet to Shape Key Editor.
• Set the End Frame to 100.

• On Frame 0 set your Key to 0, on Frame 100 set your Key to 100

• Create the Lattice as stated above.
• Add an Armature along your Lattice. Add an Armature Modifier to the Lattice.
• Add Vertex Groups and assign them according to the Bones of your Armature.
• Create an Armature Deformation as explained in the Armature deformation section.

• Depending on the complexity of your deformation, it might be easiest to apply the Lattice Modifier to your Mesh as Shape Key. In the previous example case it would be the best option as there is only one important movement.
• If you choose to do so, the animation has to be set up for your mesh again.
• Simply export the mesh as you would a normal glb.
• This example of a more complex deformation consists of a Lattice deformed through an Armature combined with a Mesh with Shape Key Deformations.
• Click on your Mesh and export it as .abc (Alembic) and .mdd (Lightwave Point Cache)

• For both Exports, make sure Start and End Frame align with your Deformation and the following settings are checked.

• Import the .abc . Click on the imported mesh and with it still selected, import the .mdd.
• The Deformation should now be fully converted into Shape Keys. You can now delete the Point Cache Modifier from the imported mesh.
• Check for any unnecessary frames that might've been added during the import. Usually an additional frame will be added at the end of the deformation, in this case frame 101. Delete them.
• Set the End Frame to 100.
• You can now export your mesh as glb

Lattice deformations can be exported as a deformation.json. In the Creator this can be used across products without needing to export each of the meshes individually. You can find the Exporter in the ig. Tools repository.

• You can refer to this guide for setting up brushes. sculpttexturesetup.pdf
• Blend file with ready-made brushes that can be appended to your current blend file : https://nextcloud.intelligentgraphics.biz/index.php/s/kMDgfPDxEgapMki
• Guide on how to append data : appending_data_from_other_blend_files
• Note: If you find your brush not working properly try changing the Mapping found in the Texture settings of the brush. Most brushes work best the Mapping set to Area/ View Plane or Tiled. See the Blender documentation for more infos.
• If your brushes still have unpredictable behaviour check if there is any scaling applied to your mesh.
• Blender Doc for textured brushes https://docs.blender.org/manual/en/latest/sculpt_paint/brush/texture.html
• You can also download the individual brush textures from here : https://nextcloud.intelligentgraphics.biz/index.php/s/AgemeEKeJ6pc9px

• Before baking normal maps, it is important that your mesh has a reasonable UV mapping that you can work with.
• Head into the Object Data Properties and add a new UVMap. Renaming is optional, but done here for clarity.
• Make sure the normal UV map is below the UV map adjusted to your patch size.
• Unwrap your geometry. Usually it is not necessary to adjust the positions or scalings of the UV. You can however adjust the space between the UV islands by adjusting the margin. Keep in mind that normalmap details might get lost the smaller your islands get.

• After your UV maps are set up, duplicate your mesh and add a Subdivision Modifier. Decide on the Levels Viewport based on the resolution of your initial mesh ~4 is a good middle ground for sculpting.
• Apply the modifier and sculpt the details to your liking.
• For a guide on how to set up brushes for sculpting see setting_up_brushes_for_sculpting
• If you find that textured brushes leave streaks or artifacts, you might need to add another Subdivision modifier.
• Some tips for Sculpting:
• Shift + LMB sets the brush to smoothing mode
• Ctrl + LMB changes the direction of the brush ( add / subtract)
• F to change the brush size
• Shift + F to change the brush strength
• In Viewport Shading enable Cavity and Depth of field to get a more pronounced shading and better view of your sculpt. Play around with the settings to your liking.

• Select your initial object and go into the Shading tab.
• Create a new material and add an Image Texture.
• On the Image Texture node click 'New'. Use the default resolution of 1024×1024 if not required otherwise.
• Confirm with 'OK'.This will be the texture your normal map will be baked on.
• Change the Color-Space to 'Non-Color'.It is not necessary to connect the Image Texture node and the Principled BSDF node that appears when generating a new material.
• Head to the Render Properties and change the Render Engine to Cycles.
• Scroll to the bottom until you see 'Bake'
• Change the Bake Type to Normal.
• Put a check on 'Selected to Active'

• Your setup should now look something like this:

• In the Scene collection, select your sculpted mesh and then select your base mesh. The order is important since it determines the active object.
• Click on the Image Texture node to select it. You can now click on 'Bake' 

• Depending on the complexity of your mesh and how strongly your sculpted mesh differs form the initial mesh it might be necessary to use a cage.

• To create a cage, duplicate your initial object.
• In Edit Mode select the whole mesh.
• Click Shrink/Flatten or Alt+S and adjust the size until it completely covers the sculpted mesh.
• Hint: pressing shift while scaling the mesh makes it easier to accurately change the scale.
• In the Bake settings, unfold Selected to Active and put a check on Cage.
• Select the mesh you just scaled as cage object.
• Select the Hires mesh followed by the initial mesh and click 'Bake'.

Any minor artifacts or disruptions in the map can also be adjusted in an image editing program such as Gimp or Krita. For further details on cages, see: https://docs.blender.org/manual/en/latest/render/cycles/baking.html

• Create a bump map with your desired details. This can be done from scratch or by converting an existing image to a bump map.
• You can use tools such as Inkscape, Gimp or Krita for vector and raster image editing.
• Upload your image to https://cpetry.github.io/NormalMap-Online/ to generate a normalmap out of your bump map.

For more info on alpha maps see : alpha map

• Select a face loop that follows the path of your desired seam contour.
• If your base mesh does not have any face loops that directly fit the seam contour, adjust your topology accordingly. Try to limit your adjustments to loop cuts and cuts with the knife tool as to not change the general shape of the mesh too much. It is recommended to do this on a duplicate of your base mesh as these edits could cause unwanted shading changes you don't want on your base mesh.
• Press 'shift + D' to duplicate the selected faces.
• Press 'P' 'Selection' to separate the selected faces into a new mesh.
• Clear any seams that might have transferred from your base mesh with 'ctrl + E'. Mark new seams depending on the seam contour. If your seam mesh consists of one single consistent face loop, only one edge as seam is necessary.

• Hint: The edge rings of your face loop should be of similar length to ensure a uniform size and thickness of the seams. You can adjust the length of your edge rings witht the help of the 'Mesh Tools' add-on. It is default to blender and only has to be enabled in the preferences.
• To do this, select a single Edge along your loop (1).
• Click 'Select' → 'Select Loops' → 'Edge Rings'. Now all edge rings along your loop should be selected (2).
• On the Sidebar click 'Edit' → 'Mesh Tools' head into 'Edge Tools' → 'Set Edge Length'. You can now set a target length that will be applied to all selected edges. (3)

• Unwrap your loop.
• Choose a face and straighten it. Select the face. Right Click aynwhere in the UV editor and click 'Follow Active Quads'. Your whole UV should now be straightened.

• Scale and position your UV according to the texture you want to use for the seams.

• Hint: If you notice your seam clipping into the base mesh, select your seam and head into Edit Mode.
• Click 'A' to select all.
• Press 'alt+S' and scale the mesh just barely enough so that it doesn't clip anymore.

• Create a simple shape with the intended dimensions of your pillow.
• Subdivide the mesh in Edit Mode or by applying a Simple Subdivision Modifier.
• Note: The right object is not a plane, but two planes merged at the outer edges, leaving a space in the middle to create a mesh with volume.

• Add a Cloth Modifier.
• Head into the Physics tab and enable 'Pressure'
• There are two ways you can approach the settings for the simulation:

• Create a plane below your pillow
• Add a Collision modifier to the plane
• In the pillows Phyiscal tab enable 'Custom Volume' under Pressure and 'Object Collisions' under Collisions
• Adjust Pressure and Target Volume to your liking

In Field Weights set Gravity to 0.

• You can now start the simulation.
• For both cases play around with Pressure and Physical Properties such as Vertex Mass until you’re satisfied with the results.
• Apply the Cloth Modifier.
• Refine your Mesh with a Subdivision Modifier and add further details such as seams in the Edit Mode.

Hint: Once you’re happy with the Values of your Modifier you can save them as a Preset which can then be loaded if you ever want to use the settings again. Keep in mind that it only saves Physical Properties, Stiffness and Damping

• Start out the same as stated above. Add loop cuts around the area where your buttons / quilts would be.
• Select the vertices that indicate the location of the buttons. Assign them to a new vertex group.

• Set up the modifiers as stated above.
• In the cloth modifier properties head into 'Shape' and enable 'Pin Group' by selecting the vertex group you just created. Edit the properties as necessary.

• Run the cloth simulation as usual.
• This method gives you a great base for modeling out further details.

• For a better understanding of real-world objects to be modeled, sometimes visuals of the products are provided by the client. Please ask your project manager for them.
• To add an Image to Blender click Add → Image → Reference
• The Image will be positioned according to your current view but can be transformed like any other object.

• The Face normals should be pointing outside to avoid any backface culling.
• If the normals are pointed inwards, it means that the normals should be flipped or it will look like the hollow square below.

• To display the Face Orientation enable the 'Face Orientation' in the Viewport Overlays.
• Red shows the inside facing normals, which will be see-through, while blue shows outwards facing normals.

• To fix this issue, head into edit mode and select the faces with flipped normals. Click on 'Mesh' → 'Normals' → 'Flip' or use the shortcut Alt+N then select 'Flip'.
• Depending on mesh complexity and situation it might be easier to select the whole mesh and select 'Recalculate Outside' instead.

Note: Mirroring an Object by using 'Object' → 'Mirror' or by applying a scale of -1 will flip the entire orientation during export. Therefore it is important to check both scale and face orientation before exporting a geometry !

“Magic UV” is a default Blender addon that only has to be activated in preferences, it is a helpful tool for setting the preferred patch size of a geometry. To set a specific patch size follow these steps:

• Add plane with the dimensions of your desired patch size e.g. 15×15 cm
• Assign a material to the plane. It should have the same resolution as the material texture you intend to use for your geometries.
• Select the plane in Edit Mode press U → World Scale → Measure
• Note: Check the Scale of your plane; for the measuring to work properly the scale has to be 1.
• Select the object you wish to apply the patch size to and unwrap it.
• In Edit Mode press U → World Scale → Apply Same Density

You can apply the scale to multiple objects at the same time by having them opened in edit mode simultaneously.

Sometimes there can be channel issues while baking normal maps, resulting in greenish-looking artifacts. Usually these can be fixed by using a cage or adjusting the extrusion distance in the bake settings, but occasionally they are hard to get rid of. A quick fix for this is to use an image editing tool.

1. Open your baked normal map in your desired image editing tool.
2. Add a new layer and fill it with the neutral normal map blue.
3. Set the Layer Mode of the new layer to the following, according to your tool.

• Krita : Hard Overlay (Found under Mix Blending Modes)
• Gimp : Hard Light, Linear Light
• PaintTool SAI: Burn/ Dodge

The channel artifacts should now be fixed. Save the normal map and use as usual.

• Appending is a function in blender which allows you to easily add data blocks (e.g. Materials, Brushes or Objects) form different files to your desired blender file.

• In the blend file you want to append the data to, head into the menu and click on File → Append

• Select the blend file with the data you want to append and confirm with double click or 'Append'.
• Choose data block you want to append from eg. Textures.
• You can now see an overview of the existing contents.
• Select your desired data and click append. You can also select all by pressing A.

• The data will now be added to your currently opened blend file.
• For further info see the Blender Doc. on Link & Append : https://docs.blender.org/manual/en/latest/files/linked_libraries/link_append.html

Sometimes a strong deformation can cause harsh UV stretching. In these cases, some extra steps need to be taken to ensure a clean UV.

• Set your timeline to the frame of which you want to adjust the UV mapping to. In this case the most extreme point of deformation is frame 100.
• Save the Armature Modifier as Shape Key. Disable or remove the Armature Modifier for the time being.

• Set the value of the Armature Shape Key to 1.00.

• In the UV Editor, select only the area that is affected by the stretching . Unwrap and Scale as usual.

• Delete the Shape Keys, starting with the Armature Key. Re-enable the Armature Modifier.You should now have a clean UV for your deformation.