Soft Outline renders outlines by generating a silhouette of an object and applying a dilation/blur effect, resulting in smooth, soft-edged contours around objects.
✅ Advantages
Soft Edges: Good for rendering soft/glowy outlines, but also supports solid outlines.
Object Exclusion: Easily select which specific objects should receive an outline.
❌ Disadvantages
Inner Lines: No inner lines are rendered. Only outlines.
Performance: Expensive to get wide outlines due to the screen-space blur/dilation that happens.
Multiple Styles: All outlined objects in the scene will share the same thickness as well as some other settings.
The Soft Outline Settings object contains the settings related to this outline effect. Here are all of the settings explained. In Unity, each setting also has a tooltip which shows more information.
General Settings
The general settings apply to the outline effect as a whole (with all sub-outlines included).
Setting
Description
Additional Information
Stage
Controls when the render pass executes.
Show In Scene View
Sets whether to render the pass in the scene view.
Force Clear Stencil
Force clear the stencil buffer after the render pass.
Should normally not be enabled, but can be used if you notice unexpected interactions between different effects.
Debug
Which stage to render as a debug view.
Shared Outline Settings
Some settings related to the visuals of the outline are shared between all outlines. This is because Soft Outline is a screen-space effect.
Setting
Description
Additional Information
Blend
How to blend the outline with the rest of the scene.
Type
Whether to render a soft or a hard outline.
Color
The color of the outline.
Hardness
The hardness of the outline.
Intensity
The intensity of the outline.
Method
The method used to dilate the outline.
Width
The width of the outline.
Spread
The spread of the Gaussian kernel (Gaussian Blur).
Passes
How many blur passes to perform (Kawase Blur).
Outline Settings
To add an outline, click on the Add Outline button. This will add an outline to the list. You can add as many outlines as you want. See the Performance section for more information about the impact of adding outlines.
Each outline in the list is applied to objects that belong to the specified Rendering Layer Mask. See Outline Layers for more information about how the layer system works.
The outline settings apply to a specific outline.
Setting
Description
Additional Information
Layer
The rendering layer(s) which will get an outline rendered for them.
The Soft Outline effect supports both a soft and a hard outline type.
Soft: A soft and glowy outline that fades out towards the edges. Supports multiple colors.
Hard: A hard outline where the alpha is cut off at a certain threshold. Supports a single, shared color.
❗ Hard Outline = Shared ColorWhen using the Hard outline option, the color is shared between all outlines in the list. If you need multiple Hard outlines with different colors, you can use multiple Soft Outline effects, but this will have an effect on Performance. Contact me if you have additional questions about this.
The Soft Outline effect renders outlines by generating a silhouette of an object and applying a dilation/blur effect. There are several options available to control how the silhouette is dilated.
Box
A box blur is applied. Controlled through a Width parameter.
Gaussian
A Gaussian blur is applied. Has an additional Spread parameter. Results in smoother outlines at a slight performance cost.
There are some known limitations that come with the implementation of the Soft Outline effect.
‼️ Hard Outline ColorWhen using the Hard outline type, the color of the outline is shared between all outlines.
‼️ Outline BleedingBecause the silhouette is dilated in screen-space, the outline will not always completely respect the configured Occlusion State. This is especially apparent for wide outlines.
In the example below, the outline is set to render When Not Occluded however the outline bleeds slightly over the other object in the scene.
Soft outline works by generating a silhouette of an object and applying a dilation/blur effect. The result is a smooth, soft-edged contour. However, due to the screen-space dilation/blur, there is a performance impact. Soft outline comes with 4 dilation methods, each working a different way and having a different performance impact.
Box Blur
Performs a two-pass blur on the silhouette, once vertical and once horizontal. This blur works by taking multiple samples around a center sample, and averaging the result.
For each blur pass (2 in total), the silhouette texture is sampled outlineWidth * 2 + 1 times. For example, if the outlineWidth is equal to 2 then the silhouette texture is sampled 2 * 2 + 1 = 5 times. This means that the performance cost of this shader increases linearly with the outline width.
For each sample, the weight of the sample is simply 1 / number of samples and so does not need to be calculated.
Gaussian Blur
Performs a two-pass blur on the silhouette, once vertical and once horizontal. This blur works by taking multiple samples around a center sample, and averaging the result, weighted according to a Gaussian distribution around the center pixel
For each blur pass (2 in total), the silhouette texture is sampled outlineWidth * 2 + 1 times. For example, if the outlineWidth is equal to 2 then the silhouette texture is sampled 2 * 2 + 1 = 5 times. This means that the performance cost of this shader increases linearly with the outline width.
Additionally, for each sample, the weight of the sample is calculated.
Kawase Blur
Performs a multi-pass blur on the silhouette. This blur works by taking 5 texture samples in total for each pass. Increasing the outline width, does not influence the number of samples taken, but instead increases the number of passes.
For example, if the number of passes is set to 3 in the settings, then 3 * 5 = 15 texture samples will be executed.
This means that the performance cost of this shader increases linearly with the outline width.
