Blender Freestyle is one of the most powerful and underutilized tools in the entire software.
It allows users to add interesting outlines and cool effects to renders, and when utilized correctly can create unbelievable results, such as sketches, architectural blueprints, and comic book backgrounds. In this guide, I'll go over everything there is to know about freestyle and how to properly use it.
Freestyle Does Not go With Everything: A lot of people will start with freestyle by taking one of their favorite renders, turning it on, and expecting it to be better. This does not work. Freestyle goes well when it's used appropriately, with a scene or objects that support the chosen style. Generally, when using freestyle, you want to stray away from realistic scenes, or anything that has high levels of precise detail.
One Style Does Not Fit All: Freestyle supports infinite combinations of different line styles and effects, but it's easy to find one thing you like and use it for everything. Experimenting with different styles is key to getting good results in any situation.
It's Not Perfect: There are still a few rare bugs with freestyle, and weird things will happen. Unfortunately, there isn't much that can be done about that, so the best thing to do is work around bugs when they happen.
To turn on freestyle, go to the Render Properties tab on the side panel and click the checkbox next to Freestyle. You should see this:
Here is where you can set the line thickness mode. Absolute: The line thickness stays a constant pixel size, not changing with render size Relative: The line thickness is set relative to the size of the rendered image Either one is fine for this, but I'll be using Relative since I find more consistent. For now, the Line Thickness can be kept at one, since there are better and more dynamic ways to set the line thickness later on.
Now, go down to the View Layer Properties tab. You should see that there's a new menu for freestyle with an overwhelming set of options:
There's a lot to take in, so for now set up a nice simple scene so the options can be visually explained one by one. My base render looks like this, but it can look like anything as long as there's simple geometry:
The first several options aren't very interesting and won't change much, so I'll explain them now: Control Mode: Allows switching between a Parameter Editor and a Script Editor. For now, scripting freestyle is new to me too so we'll stick to the Parameter Editor View Map Cache: This saves the geometry data needed to compute the outlines into a cache, which speeds up performance when the geometry hasn't changed. This is good to turn on when just messing with line styles and settings, as it speeds up performance after the first render As Render Pass: Renders freestyle to a separate render pass to be tinkered with in the Compositor. This will be used later, but for now leave it off. Crease Angle: This changes the angle cutoff for how sharp or smooth something needs to be to be recognized as a line. With an angle of 180°, freestyle acts as a wireframe outline, highlighting every edge:
Face Smoothness: Turning this on will make the crease angle also account for if a face is smooth or not. Here's the same scene as above, but now with Face Smoothness on:
Culling: Turning this on will ignore out of view and other non-visible geometry. This will rarely be turned off The Advanced Options don't normally make a difference, and should only be used in very specific situations. For most people, messing with them will never be a necessity.