Key/fill/rim concepts
Use key, fill, and rim lights to define form, open shadows, and separate subjects in 3D renders for paint-overs.
What it is
A key light is the main light source. It sets the light direction and shows most of the form. You place it first and choose its angle and height. In a character scene, it may light the face or body. In an environment, it may be the sun or a main window.
A fill light is weaker and softer. It opens shadows so planes remain readable without flattening the scene. Fill can come from a large, dim area light, bounced light, exposure adjustments, or environment light.
A rim, or back, light sits behind or beside the subject. It catches edges such as shoulders, hair, or silhouettes and separates them from a darker background. You can vary light strength and color while keeping each light's role distinct and adjustable for overpainting.
Why it matters
Clear light roles organize the render's information. Weak control can produce equally strong lights, crushed or missing shadows, and silhouettes that blend into the background. The result gives you less control over focus and may require repainting the lighting during the paint-over.
You can check it when
- ✓Identify the key, fill, and rim in your 3D scene, or record why you chose not to use a rim.
- ✓Turn off each light separately. The key should remove the main form definition, the fill should deepen the shadows, and the rim should reduce subject separation from the background.
- ✓Check the rim on the form. It should appear where the light grazes the subject, without creating a glowing outline around unrelated edges.
- ✓Review a quick paint-over for a defined light direction, readable shadows, and subject separation.