Radial Blur

Overview

The radial blur effect allows you to mimic the look of a shockwave coming from an explosion. The effect blurs the screen in the direction eminating from the center of the radial blur actor that is placed in the scene.

Settings

A RadialBlurActor can be placed in the editor or spawned through gameplay script.

The following properties are exposed to control the behavior of the blur:

Material

The opacity channel of the specified material is used to scale the size of the blur vector.

DepthPriorityGroup

The scene depth priority group layer where the effect should render. Eg. setting this to SDPG_Foreground will affect all primitives and setting it to SDPG_World will not affect the SDPG_Foreground primitives.

BlurScale

Globally scales the blur amount generated for the effect. This scales the size of the velocity vectors generated for the blur.

BlurFalloffExponent

Determines the falloff rate of the blur amount from the center of the effect.

BlurOpacity

This is only used when bRenderAsVelocity is False and determines the alpha blending amount for the rendering of the blur effect.

MaxCullDistance

Determines the distance from the view origin to the blur effect where it will no longer be rendered. The effect is faded out based on the DistanceFalloffExponent to this MaxCullDistance threshold.

DistanceFalloffExponent

Exponential falloff based on the distance to the current view origin. Higher values produce a faster falloff rate. This setting along with the MaxCullDistance determine the amount of blur generated based on distance.

bRenderAsVelocity

If True then the effect is rendered using the velocity pass of the motion blur post process effect. For more information see Blur Methods Available.

bEnabled

Toggle to determine if the effect should be attached to the scene and rendered.

Blur Methods Available

The blurring is done using two different possible methods:

• Sampling of scene color buffer directly
• Relying on the blur pass from motion blur

The advantage of using the scene color buffer directly to blur each radial blur actor separately is that it has better precision and it allows for proper blending between multiple radial blur effects active on the screen. This method also does not rely on the motion blur effect being enabled. The disadvantage is that there is a performance hit from the required resolve operation of the scene color buffer as well as the extra texture sampling needed for each radial blur pass.

By relying on the motion blur post process effect to generate blur cost of the radial blur effect simply comes from rendering the blur vectors to the velocity buffer. There is no extra rendering cost required for resolving the scene color and extra texture samples since this is already done for the motion blur effect. The disadvantage to this method of blur is that there is slightly less precision since the velocity vectors are stored as 8 bit values and there is no blending between multiple blur effects. Since there is no blending of overlapped blur effects, only the one that is strongest and closest to the view is rendered.