Rays Node

Rays takes the input image, identifies the bright areas (through a threshold), then stretches those pixels outward from a central point - like a zoom blur, but only on the highlights. The result: light rays that create the illusion of atmospheric particles (haze, dust) scattering the light.

It is a powerful visual effect that can turn a flat image into a cinematic scene. Use it sparingly - too strong and the effect becomes cheesy.

• Effects Library: Tools > Effect > Rays
• Quick add: right-click in the Node Editor → Add Tool > Effect > Rays

1. The node examines each pixel and compares its luminance to the Threshold.
2. Pixels above the threshold become ray sources.
3. These sources are stretched outward from the Center (X/Y), with an intensity that falls off according to Decay.
4. The result is blended with the original image through Blend.

• Image Input (orange) - the source image containing the bright areas. Works best with an alpha channel on the emitting areas.
• Effect Mask (blue) - optional. Limits the rays to an area (e.g. only from the window).

God rays from the sun:
MediaIn (sky shot) → Rays (Center = sun position, high Threshold) → MediaOut

Light through a window (mask):
MediaIn → Rays ← Polygon (window cutout) as Effect Mask
         ↓
     Merge Screen over the original MediaIn

Backlight on a character:
Character alpha → Rays (Center behind the character) → Merge Screen

Center (X / Y)

Origin point of the rays. A crosshair you can move in the viewer. Usually placed outside the frame to simulate a distant source (off-screen sun) or on a visible source (lamp, window).

Decay

Length of the rays. High = short, focused rays; low = long rays that cross the image.

Weight

Falloff curve (how the intensity drops with distance). Controls how hard the transition is between the light source and the ends of the rays.

Exposure

Overall brightness of the rays. Raise it for a stronger effect.

Threshold

Luminance threshold for emitting rays. High (close to 1) = only the brightest highlights emit, a subtle effect. Low = many areas emit, an overall but saturated effect.

Blend

Mix between the original image and the image with rays. 0 = no effect, 1 = rays only. Typically 0.4-0.7 for a natural amount.

Red / Green / Blue / Alpha

Emitting channels. Uncheck G and B = rays only on the Red channel (warm look).

• God rays through clouds - Center placed where the sun breaks through, high Threshold (0.8), medium Decay = bright diverging rays. Blend 0.5.
• Light through a window (interior) - a mask on the window → Rays with the Center on the window = a volumetric light shaft entering the room. A film noir or mood film classic.
• Sci-fi backlight - the character's alpha → Rays with the Center just behind = a crown of light, as if the character were strongly backlit.
• Lightsaber / energy portal - the bright area of the weapon/portal → Rays cast from that area = a volumetric aura that spills out.
• Explosion / flash - a short flash with Rays animated in intensity = a more organic burst of light than a simple flare.
• Underwater / glowing haze - light scattered in water or fog, Rays with a low Decay (long rays) to simulate atmospheric scattering.

• High Threshold = clean - start at 0.8-0.9. Lowering it gives more rays but loses selectivity.
• Center off-frame for a distant sun - placing the Center outside the frame simulates a very distant source (the sun). Inside the frame = a visible / nearby source.
• Blend 0.5 by default - Blend 1 looks like a filter effect, not real light. Keeping the original image at 50% preserves realism.
• Animated rays = dust - animating the Center position very slightly (+/- a few pixels) adds life and simulates particles moving in the light.
• Combine with an animated Fast Noise - multiplying the Rays result by a very subtle Fast Noise adds intensity variations to the rays (more believable than perfectly uniform rays).
• Red channel only for a sunset = warm rays without touching the blue of the sky.
• Work on a light pass - extract the highlights (Color Corrector with a negative lift on the shadows), apply Rays, then Screen over the original image. Cleaner than Rays applied directly to the shot.
• Limitations: Rays is a 2D effect. For real 3D volumetric light (that reacts to geometry), use the light rays of the 3D renderer with a Spot Light.