Simple Light Source

No model, no download, no VRAM cost - this node just draws a gradient. But it's drawing a specific kind of gradient: IC-Light's fbc checkpoint reads a light map literally, where white is the light source and the gradient direction tells it where that light is coming from. LightSource is the quickest way to generate that map without opening an image editor.

How it works

Pick a direction - eight options: Left, Right, Top, Bottom, and the four diagonals - and it renders a gradient running from start_color at the light's origin to end_color at the far side, at your chosen width/height. It's a plain image out, nothing IC-Light-specific happens inside this node itself; the relighting logic lives elsewhere in the graph. This node's whole job is giving you a controllable stand-in for "here's where the light is" without hand-drawing one.

The inputs and outputs that matter

• light_position - the direction: Left Light, Right Light, Top Light, Bottom Light, or one of the four corners.
• multiplier (default 1, up to 100) - intensity of the gradient.
• start_color / end_color (hex, default #FFFFFF → #000000) - white-to-black by default, matching the white-is-light-source convention; change these if you want a coloured light.
• width / height (default 512) - IC-Light's native resolution is roughly 512–768px, so the defaults line up with what the model actually expects; match it to your foreground image's size.
• Optional batch_size - generate more than one at once.
• Optional prev_image - lets you build the gradient onto an existing image rather than a blank canvas, if you already have something to layer the light map over.

Output is a single IMAGE. VAE-encode it and feed it into ICLightConditioning's opt_background input (with an fbc checkpoint loaded), or just use it as a quick visual reference for a direction before you commit to a full render.

How to install it

Same pack as everything else here - ComfyUI Manager, search "IC-light", install, restart; or git clone https://github.com/kijai/ComfyUI-IC-Light into custom_nodes manually. Nothing extra to download for this specific node.

Common issues & troubleshooting

Generated a gradient and nothing relit. That's expected - this node only draws an image, it doesn't touch your model or your subject. You still need LoadAndApplyICLightUnet to patch your model and ICLightConditioning to actually wire the light map in.

Direction doesn't match what you'd expect from the preview. IC-Light's directional control biases the initial latent, so the visual gradient is a proxy for the effect, not a 1:1 preview of the final lighting - small differences between what you see here and the final render are normal.

Want the fbc background-conditioning path but colours look off. Remember fbc is the checkpoint that bleeds background colour into the subject regardless of how clean your gradient is - that's a known tradeoff of the model, not something to fix on the LightSource side. If it's a problem, describe the light in your text prompt with fc instead and skip this node.

Size mismatch errors downstream. Match width/height here to whatever you're feeding as the foreground in ICLightConditioning - IC-Light conditions per-pixel, so mismatched dimensions will bite you at the encode step.