In this article I want to cover my top 10 tips for working effectively with weight painting. You might also find something that you didn't know you could do to create the weight paint you wanted.
These are the weight paint tips we will cover:
If you ended up here and don't know much about weight paint or vertex groups, I can suggest that you first read this article that covers what you need to know about vertex groups and also scratches the surface of weight paint.
Related content: How to use vertex groups in Blender
Let's dive in!
We can set all vertices on an object to have the same weight at once. This might be useful if we want to have a starting point that isn't zero when we start to paint, or we might want to set all vertices to a value of one.
To weight paint all vertices in a vertex group, follow these steps:
We can assign any weight we want to any vertices we want this way. However it is a much more labour intense process than simply painting in weight paint mode.
Similarly to assigning a particular weight to one or more vertices using the properties panel, we can also clear all weights in a vertex group.
Follow these steps to clear all weight paint for a single vertex group:
All weight paint will now be cleared from the vertex group you selected in the list. Another alternative is to simply select the group and press the minus sign to remove the group and add a new one.
Keep in mind that if you do this, any place where the removed vertex group was used, such as in modifiers or armatures will no longer maintain its link. So, you will have to go around the interface and add the new vertex group where you want to use it.
Sometimes we need to export our weight paint to another application. We can export weight paints using the FBX file format but to do so the object needs to be parented to an armature and the vertex group need to be associated with a bone.
Related content: How parenting works in Blender
To export weight paint using the fbx file format, follow these steps:
If you are interested in learning more about fbx import and export, you can read this guide.
Related content: Exporting and importing FBX in Blender
If we want to flip weight paint from one side to the other, meaning that we don't mirror it, we just transfer it between the two sides of an object, we can do so across the X axis. Follow these steps:
This will not actually mirror what we have painted, instead it will move the weight paint from one side to the other. Essentially a flip functionality.
To mirror as we paint our vertex group, we can go to the properties panel and click the active tools and workspace tab. That is the tab at the very top. Expand the symmetry section and check "mirror vertex groups" then choose the axis you want to mirror across.
Related content: How to mirror in Blender
When weight painting it is common to simply jump over to weight paint mode and start painting without further thought. But there is actually a handful of different tools in the left-hand sidebar that we access by pressing T.
One of those tools is the gradient weight paint tool. This tool is especially useful when we are using a vertex group to distribute foliage and other objects that should be dense closer to the camera but can be less dense further away to save on memory.
Related content: Memory optimization for rendering in Blender
To use the gradient weight paint tool, follow these steps:
In the operator panel in the lower left part of the 3D viewport we also have the option to set the gradient to be either linear or radial. The radial option will create a circular area with the highest density in the middle with a gradient going outwards in all directions.
Sometimes we want to avoid weight paint to spilling over into certain areas of our mesh. In those cases it can be a good idea to limit weight paint so that can only influence certain parts of the mesh as we are painting.
While in weight paint mode we will find vertex and face selection in the header just next to the mode switch menu. By default, none of these are selected. If we choose either face or vertex here, we can make a selection and limit the weight paint to the selection only.
We are a bit limited to how we can select, but the shortcuts for selection tools such as B for box select and C for circle select work. But we cannot click a vertex or face to select it since the left click is dedicated to painting while in weight paint mode. Instead hold shift and click to add or remove single faces or vertices from the selection.
However, we can use Ctrl+L to select linked if we have separate parts in our mesh that we want to paint separately.
If you want to disable your vertex of face selection again you can just click the corresponding selection mode button again and you are back to weight paint modes default behavior.
If you read the previous tip you now know taht we can use the face and vertex select modes in weight paint to have our weight painting only affect selected parts of the mesh. We can also use these selection modes to hide part of our mesh even while in weight paint mode.
To hide parts of a mesh in weight paint, follow these steps:
These are some of the supported selection tools in weight paint mode.
To unhide everything you can press Alt+H.
In Blender, it is possible to transfer weights from one object to another. There are two methods. We can copy a vertex group from one object to one or more other objects using indices or indexes.
By using a modifier we can also go the opposite way and copy many vertex groups from different objects to the same object. Let's start with the first method.
This is useful when we have two objects that contain different meshes and both should have similar weight painting.
However there is one limitation, both objects need to have the same number of vertices.
Each vertex has an index. The vertex group is copied so that the vertex with the same index in the target mesh is going to get its corresponding weight from the mesh we copy from. Therefore it rarely makes sense to copy vertex groups between objects that are not identical.
The vertex group might look completely different depending on the order of index for the vertices.
To copy weight paint from one object to another, follow these steps:
The other way to copy a vertex group from one object to another is through using the data transfer modifier. This method is explained in this article but for completions sake I will also list the steps here.
Related content: How to use vertex groups in Blender
To copy weight paints from one or more objects to another using the data-transfer modifier follow these steps:
This way we can use various other mapping methods that makes more sense when we are transferring vertex data between objects that are not similar. We can map using various kinds of distances instead of the index number.
If we need to convert a weight painted vertex group to vertex color data we can do so thanks to an add-on that you can get here:
External content: Vertex color master for Blender (Github)
Once the add-on is installed and activated (something you can learn how to do in the link below) follow these steps to convert a vertex group to vertex color.
This is useful, for example, if we need a vertex group to be accessible in a Cycles or Eevee material. We cannot directly access vertex groups, but vertex color can be used through either the attribute node or the slightly newer vertex paint node.
Instead of manually painting or assigning vertex weights through the properties panel, we can also use a texture to automatically create the weight paint for us.
To use a texture as a weight paint follow these steps:
This is an easy way to create a vertex group that can match any texture. In the modifier you can set the texture coordinates. For example, you might want to use UV if you are doing this with an image texture.
In this article we went through a lot of different techniques related to weight painting and vertex groups. There is a lot we can do with weight painting and there are many places in Blender that support them to mask different sections of a mesh.
Thanks for your time.