📏 Fast Sobel Sharpen

FastSobelSharpen is the most niche of the VRGameDevGirl sharpen trio, and it earns its niche. Where unsharp masking boosts all high-frequency detail, the Sobel version detects edges first - horizontal and vertical gradients - and boosts contrast only along those boundaries. The result is a "punchier" sharpening that makes outlines and structure pop, at the cost of texture: flat areas stay flat, which is exactly what you want if your footage is busy or organic (hair, fabric, foliage) and you don't want to sharpen every pore and thread into noise.

The name comes from the Sobel operator, a classic image-processing filter that approximates the gradient of image intensity - a 3×3 kernel pair, one for the x-axis, one for the y-axis, which the pack combines into an edge magnitude map. That map is then scaled by strength and added back onto the original. It's a gradient-based edge enhancement, and it's cheap: per-pixel convolutions, no learned weights, no model download.

The inputs that matter

• images - your IMAGE frame tensor.
• strength - 0.0 to 2.0, default 0.5. Edge amplification. Stay modest on video; above ~1.0 you'll start seeing edges outlined like a cartoon.
• use_gpu - off by default. CPU is fine for the batch sizes you'll realistically feed it. Turn it on only if CPU is your bottleneck.

Output is a single IMAGE tensor of identical shape.

When to actually use it

Honest take: for general "video looks soft" sharpening, you want FastUnsharpSharpen first - it's less artifact-prone. Sobel shines when:

• Your footage is organic and you want structure without texture noise.
• You're doing line-art, architectural, or graphic-heavy shots where edge contrast is the whole game.
• You've got an AI generation that's mushy in the middle but has decent outlines - Sobel rescues the outline without baking in mush.

Install

Same pack, same drill:

cd ComfyUI/custom_nodes
git clone https://github.com/vrgamegirl19/comfyui-vrgamedevgirl

Or search vrgamedev in ComfyUI Manager, install, restart.

Troubleshooting

• Edges look like bad line-art: strength too high; back down to 0.3–0.5.
• No visible effect: Sobel only amplifies actual edges - if your shot is a slow gradient (a sunset sky), there are no edges to boost, so nothing happens. That's not a bug, that's the node working as advertised.
• Flicker between frames: since Sobel is edge-driven, its effect varies with scene content. If a camera move causes visible pumping, lower strength or switch to unsharp.

It's the smallest-use-case node of the three sharpeners, but when the case fits it beats the alternatives. And unlike the fancy learned sharpeners floating around, it's deterministic, instant, and won't surprise you on the hundredth frame.