Grease Pencil Stroke vs Fill Materials in Blender
In Blender Grease Pencil, materials are divided into two fundamental components: Stroke and Fill. While Stroke materials control the appearance, color, and behavior of the outer lines and vector paths you draw, Fill materials dictate the color, gradient, or texture used to cover the enclosed area inside those strokes. Understanding how these two components work—individually and combined—is essential for creating clean 2D line art, cel-shaded animations, and textured concept art.
What is a Stroke Material?
A Stroke material defines the visual properties of the vector path itself. When you draw a line with a Grease Pencil brush, the stroke component determines how the line rendered along the drawn points looks.
- Path-Based Rendering: The stroke follows the exact path, pressure, and point-density created by your drawing input.
- Line Attributes: It governs the color, opacity (alpha), line thickness, and caps (round, flat) of the outline.
- Texture and Patterns: Stroke settings allow you to apply textures along the length of a stroke, enabling effects like pencil roughness, chalk, ink bleeding, or dashed lines.
- Pixel Alignment: Strokes can be configured to maintain consistent pixel sizes regardless of camera distance or scale with scene geometry.
What is a Fill Material?
A Fill material defines the interior surface enclosed by a Grease Pencil stroke. It automatically calculates the boundary formed by the points of a closed (or nearly closed) path and floods the interior region.
- Boundary-Based Rendering: Fill relies on the geometry perimeter to establish where the color begins and ends.
- Fill Styles: Fill materials can be set to:
- Solid: A single flat color applied across the entire enclosed area.
- Gradient: Linear or radial color transitions within the shape.
- Texture: An image mapped inside the boundary, with controls for scaling, rotation, and offset.
- Self-Overlapping Control: Fill materials handle overlapping strokes, automatically filling self-intersecting loops and complex vector shapes.
Key Differences
| Feature | Stroke Material | Fill Material |
|---|---|---|
| Primary Purpose | Defines outlines, edges, and standalone paths | Defines interior color, shading, and flat surfaces |
| Geometry Requirement | Works on open lines, single dots, and closed paths | Requires a closed or intersecting boundary to display properly |
| Styling Options | Line caps, dash patterns, path textures | Solid color, linear/radial gradients, UV textures |
| Pressure Sensitivity | Directly affected by pen pressure (opacity, radius) | Fills the bounded space regardless of stroke thickness |
Using Stroke and Fill Together
Blender allows you to toggle Stroke, Fill, or both within a single Grease Pencil material:
- Stroke Only: Standard setup for line art, sketching, hatching, and clean ink work.
- Fill Only: Ideal for silhouette blocking, flat graphic design, background elements, or painting without outlines.
- Stroke and Fill Combined: Automatically creates an outlined shape with a solid or textured center in a single brush stroke, saving time when creating stylized shapes, cartoon characters, and UI elements.