In this short tutorial we will see how to use Annotations with the Cell Fracture tool in Blender 5.
Video Transcript
Hello everyone! In this short tutorial we will see how to use Annotations with the Cell Fracture tool in Blender 5. This tutorial is intended for users who are already familiar with Cell Fracture and want to learn both how to fix the issue where annotations are not taken into account by the tool, and some general guidelines for drawing them to achieve the desired effects.
In the scene I am using, there is a simple Cube. I selected the Annotate tool and set Placement to Surface, so that I can draw lines on the surface of the object instead of in 3D space. Lines drawn outside the object will remain in space, while those drawn on the Cube will follow its surface, which is exactly what we need.
By selecting Cell Fracture from the Object Quick Effect menu and choosing Annotation Pencil mode in the Point Source section, in theory the tool will take into account circles, lines, and intersections drawn with Annotate on the object when defining the fractures.
Leaving the default settings and clicking OK, we can see that the result is not what we expected. This is the first issue we are going to fix. Cell Fracture also does not delete the original object, which I am temporarily hiding to show you the result. I press CTRL Z a few times to undo the operations and return to the original object and annotations.
To make Cell Fracture use the annotations, we need to create a second Annotation layer above the default one and define our annotations there. Annotation layers are visible in the first menu of the tool, right after the color, in the 3D Viewport.
In this menu I disable the original layer without deleting it, then I create a new layer above it and rename it, for example, Fracture. The original layer must still be kept even if it is not used for this purpose, which is why I am only hiding it. You can optionally use it for other annotations in the project.
I then draw the fractures using the Annotate tool and use Cell Fracture, making sure that Annotation Pencil is selected in the Point Source section.
This time the fractures will take the annotation lines into account. So remember to create a base annotation and hide it, then create a new layer above it and draw the fracture lines there using Annotation Pencil mode.
Now let’s look at a couple of considerations on how to draw these annotations to achieve the desired results. To create radial fractures from a specific point, we need to draw one or more concentric circles, as in the previous example. With a single circle, we will get a simple radial fracture starting from its center.
By drawing multiple concentric circles, we will still get a radial fracture originating from the center of the innermost circle, but with progressively smaller fragments up to the outermost circle. Outside of that, larger shards will form, still with a radial distribution. So it is not necessary to draw spirals or complex shapes to achieve this effect.
To get fragmentation on the other faces of the Cube as well, additional annotations need to be drawn. So far, Cell Fracture has generated Source Points only from the annotations on the main face, extending the cuts radially. This can be useful in some cases, but if you want fragments distributed across the entire object, you just need to add annotations on the other faces as well.
As you can see, after adding new annotations, the quality of the concentric circles decreases. This happens because Cell Fracture uses a limited number of fracture points to generate the divisions. The parameter that controls this behavior is Source Limit. So far, the default value of 100 has been sufficient, but with a higher number of annotations, it needs to be increased to get better results.
Before concluding, let’s consider the case of straight lines. You might want to create a precise fracture line and try to draw it directly on the object. For example, here I created concentric circles in a corner of the Cube face and a line starting from the outermost circle toward a distant vertex, with the idea of getting a fracture along that direction. However, the result will not be as expected.
The reason is that fracture lines are generated as diagonals relative to the drawn annotations. To get a fracture in a specific direction, you need to draw two annotations that meet at the starting point and extend in perpendicular directions toward two different edges of the face. Running Cell Fracture with these two lines will generate a diagonal fracture between them in the desired direction. In this example, the line does not perfectly reach the vertex because the two annotations have different lengths.
Alright, that’s it for this video! As with my other videos, the text version of this tutorial and other resources are available on my website at the link in the description. If you found this video helpful, you can support me with a Like and by subscribing to the channel. See you next time!