To Bevel Or Not To Bevel: Using Modifiers To Control Blender Subdivison Surface Edges

Controlling Edge Flow with Modifiers

When modeling assets in Blender, controlling the flow and smoothness of edges is critical for achieving a clean, optimized, and intentional final render. Blender offers two powerful modifiers that allow polygonal modelers to refine sharp edges and smooth out meshes – the Bevel Modifier and the Subdivision Surface Modifier.

Understanding when to apply these modifiers, how they function under the hood, and how to fine-tune them grants 3D artists enhanced command over their designs. Whether crafting hard surface assets full of crisply beveled edges, or sculpting smooth organic shapes, mastery over Bevel and Subdivision grants expanded creative control.

The Bevel Modifier: Smoothing Out Hard Edges

The Bevel Modifier takes angular hard edges and intersections on a mesh and smooths them out, creating either rounded or faceted beveled faces. This helps eliminate the harsh jaggedness of low poly meshes. The Bevel Modifier cuts back edges and vertices, then builds up new geometry by extruding out faces and side edges perpendicular to the original mesh.

The width of the beveled area is controlled via the Width value. A Percent value dictates if width is based on absolute distance, or relative percent of edge length. Segments controls smoothing iterations – higher values equal smoother curves. The Profile option sets whether smoothed areas utilize rounded, half-circular profiles, or hard-edged triangular chamfered profiles.

Bevel Weight and Edge Crease for Fine-Tuned Control

For more selective, customized beveling, edge attributes like Bevel Weight and Edge Crease allow for fine-grained control. Increasing Bevel Weight on specific edges causes those areas to widen and smooth more dramatically. Increasing Edge Crease sharpens designated edges, preventing excessive smoothing even with high Width or Segment values.

Used strategically in conjunction with modifier settings, these attributes allow for perfect per-edge refinement. A low Width can be set on the modifier itself to gently bevel the entire model, then Bevel Weights explicitly punched up on desired sharp edges to carve out aggressive smoothed bevels only where needed.

When to Apply the Bevel Modifier

The Bevel Modifier excels at taking hard edges and intersections and giving them a smooth, refined finish. It performs best when located early in the modifier stack, directly after main model detailing is complete. By beveling early, the smoothed areas integrate with and inform the rest of the asset creation process.

Applying Bevel late can have detrimental impacts on other modifiers and deformers located below it in the stack. Smoothed beveled faces may interact poorly with tools expecting sharp edges and vertices. Thus getting Bevel in early is key for maximizing control and flexibility downstream.

The Subdivision Surface Modifier: Smoothing Out Meshes

While the Bevel Modifier focuses specifically on edges, the Subdivision Surface Modifier smooths and subdivides entire meshes. Taking low-to-medium poly meshes as input, it utilizes subdivision algorithms to split and refine faces, outputting higher poly surfaces with enhanced smoothness. This allows fast base meshes to remain light and manageable, while still achieving finalized assets with rich detail and smooth softness.

Subdivision happens in two key ways – either through iterative edge splitting, or recursive face splitting. Blender utilizes both techniques to best preserve mesh details and attributes.

Subdividing Edges Versus Faces

When subdividing by edges, additional loop cuts are repeatedly inserted midway across existing edges, doubling and quadrupling edge counts. Spacing stays even, but edge flow topology may drift. When subdividing faces, each poly face gets split into four smaller faces – quads become 16, 16 become 64 smaller quads. Additional edge loops radiate to preserve borders.

Each method has pros and cons – edge subdiv preserves hard modeled shape details, but distorts clean topology. Face subdiv keeps topology cleaner, but loses precision on sculpted shapes. Blender leverages both techniques to maximize benefits of each.

The Catmull-Clark Algorithm Under the Hood

Driving Blender’s Subdivision calculations is an advanced recursive mathematical formula known as the Catmull-Clark Algorithm. Named for its creators, Edwin Catmull and Jim Clark, it extends polygon subdiv concepts to work smoothly across N-gons as well as quads and tris.

Without getting too technical, the Catmull-Clark Algorithm splits base mesh faces cleanly into quads. It then calculates new vertex positions along the mesh via a weighted average of surrounding points – this smooths out details and curvature. The algorithm repeats these splits and averages recursively on its own output, iteratively driving up poly counts while improving smoothness.

Optimal Subdivision Levels for Good Performance

When applying Subdivision in production, striking the right balance between smoothness and economy is essential. Too few subdiv levels leave visible hard edges and faceting – too many over-inflate poly counts, creating dense meshes that render slowly and are difficult to work with downstream.

Finding the sweet spot where meshes look optimally smooth yet retain fast responsive viewport and render speeds involves experimentation. Viewport Subdivisions under Modifier settings allows toggling Higher and Lower mesh resolutions for quick testing without full calculations. The optimal Max Subdivide value for final renders often falls between 2-4 levels.

Applying Subdiv Before or After Bevel?

When utilizing both Bevel and Subdivision modifiers on a model, order of operations impacts end results. In most cases, applying Subdivision first allows the Bevel modifier to better handle resulting topology changes.

Running Bevel on initial raw geometry often creates less than ideal intersections once smoothed and subdivided down the stack. The expanded edge flow and vertex spacing from early Subdivision gives the Bevel modifier more polygon real estate to work with. This affords smoother continuous curves on beveled edges.

Exceptions exist of course – creative workflows may dictate otherwise. But generally, smoothing via Subdivision ahead of precision edge work with Bevel makes good logical sense, and offers reliability in outcomes.

Example Setups for Common Use Cases

Understanding when and how to integrate Bevel and Subdivision into various modeling scenarios is key for controlled results. Below are guidelines and modifier stack examples for optimizing common asset types.

Bevels and Subdivs for Organic Shapes

When sculpting organic models like characters, creatures, and plants, the standard workflow is:

1. Blockout base model proportions
2. Detail sculpt main shapes and forms
3. Refine crevices and edges via beveling
4. Smooth and enhance sculpt resolution with Subdivision

The modifier stack follows suit, with Subdivision above Bevel to best adapt beveled edges across smooth surfaces:

1. Multiresolution for main digital sculpting
2. Subdivision (2-3 levels) to smooth and boost sculpt resolution
3. Bevel to refine edges and crevices
4. Edge Split to maintain some key hardened edges

Hard Surface Modeling Workflows

For hard surface models like machinery, products, and architecture, edge flow is paramount. The standard workflow is:

1. Blockout primary 3D shapes and forms
2. Model main beveled edges and mechanical details
3. Dial in specific edge bevel weights for secondary smoothing accents
4. Subdivide broader flat surfaces for added realism

Here Bevel takes precedence over Subdivision for precision:

1. Primary beveled edges modeled early
2. Bevel Modifier to refine and enhance key edges
3. Mirrored Subdivision (1-2 Levels) for broad surface smoothing

Optimizing Modifier Order for Best Results

While Subdiv then Bevel is suitable for many organic models, the optimal modifier order ultimately depends first on the characteristics of the base mesh, and secondly on the nature of the final forms and function being pursued.

For models requiring extreme precision on key edges, yet also large smooth surface areas, sometimes a layered approach works best. Higher in the stack, a low-intensity universal Subdivision pass can subtly improve baseline mesh flow. Farther down, an intense late-stage Bevel pass can override Subdivision effects along select hardened edges.

This grants the mesh best of both worlds – gently enhanced continuity from initial Subdiv, with the ability to locally inject bold beveled accents as needed. Finding right balance of global smoothing vs focused beveling, ordering things just so in the stack – that’s the true artistry of beveling.