3D modeling often requires using specific tools you are likely to find across many applications. One such tool is the ability to bevel hard edges to create the effect of natural smoothness across an object. So when the bevel does not work we need to immediately enquire about the cause of the issue and how to solve it, so that we can continue with the modeling process.
The most likely cause for the bevel modifier not working correctly is the result of a change to the scale values of the model. The scale value on each axis changes how the bevel modifier calculates the effect. To fix this, select the object, press Control + A, and apply the scale values of the object.
This is the most common issue when working with the bevel modifier as well as the simpler bevel tool in Blender. However, other issues can occur as well, such as the bevel modifier not affecting the object at all.
How To Use The Bevel Modifier In Blender?
The bevel modifier is the procedural version of the bevel tool, and its main function is to create smoother edges across your model.
For the traditional bevel tool, we need first to select the edges that we want to bevel and then use the hotkey Control + B to activate the bevel tool.
We can then control the size of the bevel with our mouse and the number of segments with our scroll wheel to increase the bevel smoothness.
By contrast, we have the bevel modifier, which affects the entire object like all modifiers. Rather than adjusting the values as we use the tool, the modifier allows us to control the parameters in the modifiers tab of the properties panel.
Using the bevel modifier, we can adjust the width type that affects the calculation for the parameters below.
We can change the bevel size by controlling the amount value, which is largely influenced by the chosen width type.
Also available to us is the segments option, which can improve the smoothness of our edges at the expense of increasing our geometry count.
Other options are more advanced here but very powerful. The limit method and angle values control which edges are beveled based on a user-defined limitation, which by default is the angle of the edge.
Even once you understand how the modifier works, you may find that it does not always work correctly.
Why Is The Bevel Modifier Not Working On My Object?
The primary issue that artists are likely to face when working with the bevel modifier is when manipulating the amount parameter in the modifier does not result in an evenly distributed bevel.
In the example below, we have two similar models that are of the same initial size and have had the bevel modifier applied to them using a value of 0.50.
Both objects were originally cubes that had been scaled up on the X axis. They both had the bevel modifier added to them with the same settings, yet the result here is clearly different.
The reason is one of these objects has had its scale applied, but the other one has not. All objects will have a default scale value of 1,1,1 on each of the three axis. Scaling will change these values and that is what affects the way the bevel modifier works.
In the image the closer object has had its scale applied while the other object has not. This one change is what has caused the change of behaviour with the bevel modifier.
The solution is to apply your scale so that the modifier functions correctly. To apply the scale of an object, select the model and use the hotkey Control + A to open the apply menu.
From this menu, select either the scale option or the rotation and scale option if you have rotated the object.
Now your object will change its appearance as any modifiers that were affected by the scale are recalculated to the new values.
What If Applying The Scale Does Not Work?
One solution is not always going to fix every problem, and sometimes even applying scale may not change anything on our model.
If the object has a lot of small faces and tight crevices, then the bevel modifier may be employing a feature known as a clamp overlap.
The clamp overlap is used to prevent geometry from overlapping itself as a result of the Bevel modifier. The image below is an example of an object that can experience this effect.
The bevel here is technically working, but the clamp overlap prevents the bevel from expanding. The amount value is pushed very high here, but does not seem to affect the model.
In the modifier, open the geometry section and you will find a tick box for the clamp overlap. Untick this box to turn off the feature and you will notice the bevel gets much larger on your model.
Here you can see why this option is turned on by default, as it prevents you from destroying the appearance of the model by preventing and geometry from crossing over.
The solution here is to keep the clamp overlap option turned on, as it is helpful based on your model. Find the value where the overlap takes effect and then work within those bounds.
If you are looking to apply a stronger bevel to areas of your model, consider creating a vertex group for the edges that you want to bevel and then change the limit method to vertex group, then select the vertex group that you created.
Alternatively this is one of those situations where the bevel tool may be more suitable than the bevel modifier, as you can select the edges that you want to bevel independently.
Hidden Overlapping Geometry
What if you applied the scale and bevel continues not to work? What if you then turned off the clamp overlap feature and the bevel still would not work? One other issue that can cause this problem is the existence of overlapping geometry.
With the clamp overlap option turned on, Blender is trying to prevent geometry from crossing over as a result of the amount parameter of the bevel modifier being pushed to far.
However, the issue of overlapping geometry could already exist on the model before we even add the modifier.
It is common to have overlapping geometry, as there are many ways that we can create the scenario of vertices and edges overlapping the same space.
In our example the bevel modifier has been added to the cube and the amount has been set to 0.2, so it should be visible on the cube.
Despite this, the cube still appears to have sharp edges. This is due to the existence of overlapping vertices.
The cause of the overlap, using the extrude tool and then right clicking to cancel the tool. Some tools, like the bevel tool and the inset tool, are cancelled if you press the right mouse button while operating the tool.
However the extrude tool is a two step process when using the hotkey, as you first create the geometry and then have to move. But it is the movement of the geometry that is cancelled, while the created geometry remains, causing the overlap.
To fix the issue, select the entire object in edit mode and press the M key to open up the merge menu. Select merge by distance from the menu and any overlapping verteces will be merged together.
If you have added the bevel modifier, you will notice the modifier take affect as soon as the overlapping geometry is dissolved.
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