Glow

Extracts bright areas and composites a blurred, tinted version over the original for a bloom or glow effect.

Category: Effects Menu path: Effects > Glow

Ports

Port	Type	Direction	Description
in	imageRgba16f	input	Input image
out	imageRgba16f	output	Image with glow applied

Parameters

Param	Type	Default	Description
threshold	scalar	0.8	Luminance cutoff for bright area extraction (0-1). Only pixels brighter than this contribute to the glow. Keyframeable.
intensity	scalar	1.0	Multiplier for the extracted brightness. Higher values produce a stronger glow. Keyframeable.
blur	scalar	20	Gaussian blur radius in pixels for the glow spread. Keyframeable.
color	color	white (1,1,1,1)	Tint color for the glow. Multiply against the extracted brightness.
blendMode	enum	Add	How the glow is composited over the original. Add: additive (brightens). Screen: screen blend (softer, non-clipping).

Expose Channels

When enabled (E button on node header), adds input ports that override params via edge connections:

Port	Type	Overrides
threshold_in	scalar	threshold
intensity_in	scalar	intensity
blur_in	scalar	blur

How It Works

The glow effect is a three-pass operation:

1. Threshold pass: Extracts pixels above the luminance threshold using a smoothstep with a ±0.1 transition band. The extracted brightness is multiplied by the intensity and tint color.
2. Blur pass: The thresholded result is gaussian-blurred at the specified radius, spreading the bright areas outward.
3. Merge pass: The blurred glow is composited over the original image using Add or Screen blend mode.

Glow expands content bounds (like Blur), so the engine computes overscan to prevent clipping at comp edges.

Usage Examples

Basic: Bloom on highlights

1. Add a Glow node after your image source
2. Set threshold to 0.7, intensity to 1.0, blur to 30
3. Bright areas (specular highlights, light sources) bloom outward

Creative: Colored glow

1. Set the color param to a warm orange for a candlelight glow
2. Lower threshold to 0.5 to include more of the image in the glow
3. Use Screen blend mode for a softer, more natural bloom

Advanced: Pulsing neon glow

1. Keyframe intensity from 0.5 to 2.0 in a sine pattern using Time + Math nodes
2. Feed the result into intensity_in via expose channels
3. The glow rhythmically pulses

Tips

• Screen blend mode prevents values from exceeding 1.0 (no clipping), while Add can push values above 1.0 for a more aggressive bloom
• Lower threshold values include more of the image in the glow -- at 0, the entire image glows
• The blur radius controls how far the glow spreads; 10-30 for subtle, 50+ for dramatic
• For cinematic bloom, use a slight warm tint color and Screen blend mode

Related Nodes

• Blur -- the blur stage used internally; standalone blur without the threshold/composite steps
• Merge -- the compositing stage; can replicate glow manually with more control
• Threshold -- similar bright-area extraction without the blur/composite
• DropShadow -- similar multi-pass architecture but darkens instead of brightens