Geometry Nodes
Group three focuses on generating the line art that forms the structural backbone of the painting effect. This group is responsible for creating visual guides through different types of lines, each capturing a unique aspect of the geometry, including contour lines, intersecting edges, crease angles, sharp edges, boundary edges, and cast shadow edges. Each kind of line art represents a distinct feature of the object’s geometry, ensuring that the strokes applied in subsequent steps meaningfully adhere to the structure of the object.
Contour Lines
Contour lines trace the outer edges of the object, defining its overall silhouette and shape. These lines are essential in establishing the basic visual identity of the object, ensuring that it stands out distinctly from the background. By emphasizing the object's outer boundaries, contour lines provide a framework that grounds the painting effect, helping to retain the original form of the object. Contour lines also assist in defining the object's depth, providing viewers with a sense of volume and dimensionality.
Crease Angles
Crease angles highlight the sharp folds or creases within the geometry, capturing intricate details that represent the object's inherent form. These lines are generated where there is a significant change in the surface angle, often at points of bending or folding. By accentuating these creases, the painting effect gains a sense of structure that ensures complex surfaces are depicted accurately. This not only adds visual interest but also conveys the material characteristics of the object, such as sharp metallic folds or softer fabric creases.
Sharp Edges
Sharp edges are handpicked features assigned by the user as sharp in the geometry nodes, which are then used to generate line art. Unlike crease angles, which are procedurally determined, sharp edges are manually selected to emphasize key angular features that distinguish different parts of the object. These lines provide a clear distinction between separate elements, such as the sharp corners of a building or well-defined edges of a mechanical part. By incorporating these handpicked sharp edges into the line art, the system retains critical structural details that contribute to understanding the form and complexity of the object.
Boundary Edges
Boundary edges mark the points where the geometry of different objects meets or ends. These lines are crucial for preserving the relationships between multiple interacting objects in a scene. For example, boundary edges are generated where two intersecting surfaces meet, allowing the painting effect to respect the visual separation between distinct elements. This helps maintain clarity in complex scenes, preventing overlapping objects from blending into one another inappropriately. By emphasizing boundaries, the painting effect can create a visual hierarchy that makes it easy for viewers to distinguish between different elements in the composition.
Intersecting Edges
Intersecting edges are produced where two or more objects overlap or intersect with each other. These lines are particularly important in multi-object scenes, where it is necessary to preserve the spatial relationship between overlapping objects. By defining intersecting edges, the system ensures that objects appear layered correctly, with appropriate visual separation. This helps convey depth and spatial arrangement within the painting effect, reinforcing the illusion of three-dimensional space.
Cast Shadow Edges
Cast shadow edges provide information about how light interacts with the object, particularly where shadows fall due to the object's geometry. These lines help guide the strokes applied later to reflect the light and shadow dynamics present in the scene. By emphasizing cast shadows, the painting effect can achieve a higher degree of realism, ensuring that shadows blend seamlessly with the rest of the visual output. Cast shadow edges are instrumental in preserving the lighting information, making it easier for the final result to convey a sense of atmosphere and lighting consistency.
Smoothing and Integration
After generating these different types of line art, they are further processed to ensure smoothness and cohesion. The lines are smoothed to prevent harsh transitions, which might otherwise make the strokes look rigid or unnatural. This smoothing process helps to blend the line art seamlessly with the rest of the animation, ensuring that the visual output retains a painterly, organic feel.
This approach to line art generation ensures that the strokes produced by the filter follow the natural form and flow of the object. The resulting lines are designed to guide the painterly effect organically, providing a visual backbone that is rich in structural information while remaining adaptable and expressive.
