How to CONNECT an object to ANIMATION BONES in Blender

In this article we are going to connect animation bones to a 3D model so that they can deform the model and animations can be made using frames.

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Starting situation

We start with a 3D model and the Armature object we want to connect to the model, you can see how to create animation bones in this other article.

3d model with animation skeleton in blender
Fig. 1: We start from a 3D model together with an animation skeleton.
3d model with subdivisions and animation bones in blender
Fig. 2: The 3D model has subdivisions so that the animation bones can deform it.

Parent 3D model to animation bones

What we have to do now is to link the 3D model to the Armature object, this is done by parenting them, it is important to parent the 3D model to the animation bones, that is the Armature object has to be the parent object, note that in figure 3 the objects have been selected incorrectly, in this case, the correct way to select them is as shown in figure 4, in which the active selection is the Armature object. For more details see the article on how to parent and un-parent objects in Blender.

selection of two objects in Blender, the active selection in yellow color
Fig. 3: Both objects are selected, the active selection is the 3D model.
selection of two objects in Blender, the active selection in yellow color
Fig. 4: Both objects are selected, the active selection is the animation skeleton.

In the window to parent the objects we select one of the options within “Armature Deform”, each one will have different effects, in this case we are going to use the basic form that would be “With Empty Groups” (figure 5) in which groups of vertices are created within the 3D model with the names of the bones.

Window to parent objects in Blender.
Fig. 5: Window to parent objects in Blender.

Once the 3D model is linked to the animation bones, select the object and go to the window where the vertex groups are located by clicking on the icon shown in figure 7.

3d model with animation skeleton in blender
Fig. 6: Once the relationship has been established, the 3D model is selected.
vertex tab of an object in Blender
Fig. 7: Vertex tab of the selected object.

In the “Vertex Groups” section we can see the vertex groups that have been created by linking the model to the Armature with the “Empty Groups” option, at this point these vertex groups have not been assigned any vertex of the model so we are going to start assigning them.

vertex groups to animate 3d model with animation bones in blender
Fig. 8: Vertex groups were created with the names of the animation bones.

Select the model and enter the edit mode, notice in the “Vertex Groups” tab that the “Weight” field appeared, which was not there before, the Weight value allows us to indicate what percentage of influence will have a particular bone on each vertex, where the value 1 indicates total control by the bone and 0 indicates that the bone does not have any control over the vertex.

3d model with animation skeleton in blender
Fig. 9: Enter the edit mode of the object related to the Armature.
vertex groups to animate 3d model with animation bones in blender
Fig. 10: The vertex group window changes slightly in Edit Mode.

Before assigning the vertices to each group I am going to show the names of the bones, for that I select the Armature object, go to the Armature properties and in the Viewport Display window check the “Show Names” box as shown in figure 11.

option to display object names in the blender viewport
Fig. 11: Activate this option to display the names of the animation bones in the Viewport.

Assigning vertices to bones

We are going to select the vertices at the top of the 3D model, those shown in Figure 12.


A set of vertices is selected to link to an animation bone in blender.
Fig. 12: A set of vertices is selected to link to an animation bone.

Con los vértices seleccionados vamos a la ventana “Vertex Groups” y seleccionamos el grupo al cual asignar los vértices, en este caso el grupo “Bone.001” y acto seguido pulsamos el botón “Assign” que se muestra en la figura 14.

vertex groups to animate 3d model with animation bones in blender
Fig. 13: Select the group corresponding to the bone to which you want to assign these vertices.
assigning vertices to a group in Blender
Fig. 14: The selected vertices are assigned to the selected group.

Test if the bone deforms the assigned vertices

Before assigning more vertices we can do a test to see if what we did worked, for that we select the Armature object and go to pose mode, as shown in figure 16.

animation skeleton in blender
Fig. 15: In object mode the animation skeleton is selected.
pose mode in blender to animate bones
Fig. 16: Change to Pose mode to animate the bones.

In pose mode we select the bone and rotate it, if everything went well we should see that the bone deforms the vertices that were assigned to the group, as we can see in figure 17.

rotation of an animation bone producing deformations in a 3d model in blender
Fig. 17: When rotating a bone in Pose mode, the linked vertices rotate together.

Assigning the remaining vertices to the animation bones

Now we are going to select the vertices of the lower part of the model which will be totally controlled by the bone at the bottom.

A set of vertices is selected to link to an animation bone in blender.
Fig. 18: The assignment process is repeated for the vertices below.

Vamos a la ventana “Vertex Groups”, seleccionamos el grupo correspondiente y hacemos clic en el botón asignar.

vertex groups to animate 3d model with animation bones in blender
Fig. 19: Now the group corresponding to the lower bone is selected.
assigning vertices to a group in Blender
Fig. 20: The selected vertices are assigned to the selected group.

Make two animation bones control a group of vertices

For the remaining vertex loop what we are going to do is that both bones can control the vertices, for this we have to repeat the previous process but change the Weight parameter. We start by selecting the set of vertices, a quick way to select an Edge Loop is by pressing ALT and clicking on one of the edges of the loop we want to select.

A set of vertices is selected to link to an animation bone in blender.
Fig. 21: The vertices in the middle that are at the same distance from both bones are selected.

Then go to the “Vertex Groups” window and change the Weight value to 0.5.

field to select the weight or influence that an animation bone will have on a set of vertices in Blender.
Fig. 22: Change the weight with which the vertices are assigned.
field to select the weight or influence that an animation bone will have on a set of vertices in Blender.
Fig. 23: The weight is set to half.

Then we select the first group and assign the selected vertices to it.

vertex groups to animate 3d model with animation bones in blender
Fig. 24: The first group of vertices is selected.
assigning vertices to a group in Blender
Fig. 25: The selected vertices are assigned to the group with the previously selected weight.

Then we select the second group and also assign the selected vertices to that other group.

vertex groups to animate 3d model with animation bones in blender
Fig. 26: The second group of vertices is selected.
assigning vertices to a group in Blender
Fig. 27: The selected vertices are assigned to the group with the previously selected weight.

As the vertices were assigned to both groups in each of them with weight equal to 0.5 with this we have established that each bone will have a 50% influence on these vertices. In Figure 28 you can see the result of all this.

rotation of an animation bone producing deformations in a 3d model in blender
Fig. 28: The vertices of the middle respond to both animation bones.

One thing that could have been done is to assign the intermediate vertices weights of 0.25-0.75 in each corresponding group.

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