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> Samples and Tutorials > Engine Feature Examples > Blueprints > Fog Sheet and Light Beams

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Fog Sheet and Light Beams

An overview of the Fog Sheet Blueprint.

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Fog Sheet

The Fog Sheet Blueprint, shown above, consists of a Static Mesh plane with a cloudy fog Material applied to it. If you open the network in the Blueprint Editor, you will see that most of the setup is done in the Construction Script.

Each of the three aspects of the Blueprint (i.e. the Components List , the Construction Script , and the Event Graph ) are responsible for a different part of the overall effect. The following table breaks down the jobs for each aspect and how they work together to create the final result.

Blueprint Setup


Blueprint Aspect	Purpose
Components List	The only Component created within the Components List is a single Billboard Component, which provides only a selectable icon. This is used for placement in the level.
Construction Script	The Construction Script performs the following tasks: Create the sheet geometry using a Static Mesh. Read the placement of the Size variable and use it to scale the Static Mesh appropriately. Create a Material Instance Dynamic (MID) for the sheet geometry and apply it. Gather settings data for the Material from the exposed Details panel properties, apply them to the Material.
Event Graph	This Blueprint has no Event Graph , meaning that once its properties are set, it remains the same throughout gameplay.

Of particular importance in this effect is the creation of the Material Instance Dynamic (MID for short) in the Construction Script. A MID is parameterized Material that is set up in such a way that it can be edited during gameplay.

Editable Variables

The exposed ( Editable ) variables give designers control over the following properties of the Material:


Property	Purpose
Materials
Color	The color of the fog effect.
Brightness	Brightness applied to the fog color.
Opacity	How well the fog can be seen through.
Depth Fade Distance	Controls the distance away from intersecting geometry that the effect will fade. This prevents harsh cuts along walls and other surfaces.
Noise Projection Distance	Provides a depth offset for fog noise.
Noise Size	This is similar to tiling - the higher the value, the fewer tiles of the noise texture.
Panning Speed	How quickly the noise texture pans across the fog surface.
Fade Distance	The distance between the player and the effect at which the fog fades as the player approaches. This prevents the player from noticing the sheet geometry.
BP Fog Sheet
Size	This controls the size of the sheet mesh used to display the fog sheet.

The Size variable is particularly interesting in that it has had its 3D Widget enabled. The 3D Widget is a feature available only to vector variables, and creates a visible object in the Viewport that can be manipulated to change the 3D vector value.

Since a 3D Widget is simply a mechanism for controlling a Blueprint variable, the widget is only visible when it is associated Blueprint is selected. The widget can then be selected and moved using the standard Move tool. This provides a designer with a quick way of changing a vector value.

In this case, the 3D Widget is employed to allow for quick resizing of the fog sheet geometry plane. The upper right corner of the mesh meets the location of the 3D Widget, and the sheet as a whole scales from the center, where the Blueprint's sprite icon is located.

Light Beam

The Light Beam Blueprint is very similar in nature to the Fog Sheet, except that it is set up so that it can follow the rotation of a given light source and uses a slightly different Material setup. It also has no Event Graph, as all of its calculation takes place in the Construction Script.

Blueprint Setup

The Components List, Construction Script, and Event graph for this Blueprint perform the following tasks:


Blueprint Aspect	Purpose
Components List	The only Component created within the Components List is a single Billboard Component, which provides only a selectable icon. This is used for placement in the level.
Construction Script	The Construction Script performs the following tasks: Create the sheet geometry using a Static Mesh. Read the Length and Width variables and use them to scale the Static Mesh appropriately. Create a Material Instance Dynamic (MID) for the sheet geometry and apply it. Determine whether to follow the rotation of a light source, and if so, rotate the geometry accordingly. Determine which shape (parallel for Directional Lights or conical for Spot Lights) to use for the profile, and swap out the material mask texture appropriately. Gather settings data for the Material from the exposed Details panel properties, apply them to the Material.
Event Graph	This Blueprint has no Event Graph , meaning that once its properties are set, it remains the same throughout gameplay.

Editable Variables

Since this Blueprint is primarily a level design tool, most of its functionality takes place within the Construction Script. Below are the exposed variables that drive the behavior within the Construction Script:


Property	Purpose
Light Beam
Light	This gets populated with the light source that you want the light beams to follow.
Width	Controls the width of the light beam sheet.
Length	Controls the length of the light beam sheet.
Color	Controls the color of the light beam.
Brightness	A brightness factor that is applied to the light beam color.
Fade Distance	The distance between the player and the effect at which the light beam fades as the player approaches. This prevents the player from noticing the sheet geometry.
Animated	Whether the light beam material is animated; this provides the shimmering effect within the beam.
Spot Light	If unchecked ( false ), the sheet uses a parallel shape for a Directional Light. If checked ( true ), it uses a cone shape for a Spot Light.
Use Light For Rotation	Whether the light follows the rotation of the Light Actor specified in the Light property, or if it can be rotated independently.

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