Chapter 4: Advanced Modeling Techniques

Learning Objectives

• Master subdivision surface modeling
• Learn to use sculpt mode
• Understand retopology techniques
• Master boolean operations and procedural modeling
• Learn hard-surface and organic modeling methods

Detailed Knowledge Points

4.1 Subdivision Surface Modeling

4.1.1 Subdivision Surface Principle

Subdivision Surface is a technique that subdivides a low-polygon mesh into a smooth surface using a mathematical algorithm:

Low-poly mesh → Subdivision algorithm → High-poly surface

Catmull-Clark Subdivision Algorithm:

• Each face is divided into 4 sub-faces
• New vertex positions are based on the average of surrounding vertices
• Increases smoothness while maintaining the original shape

4.1.2 Subdivision Surface Modifier

# Add Subdivision Surface modifier
Properties Panel → Modifier Properties → Add Modifier → Subdivision Surface

Important parameters:
- Levels Viewport: Viewport display level (0-6)
- Render: Render level (0-6)
- Type: Catmull-Clark (smooth) or Simple (not smooth)
- Use Limit Surface: Use the limit surface

Subdivision Level Comparison:

Level	Face Count Increase	Use Case
0	1x	Original mesh
1	4x	Basic subdivision
2	16x	General use
3	64x	Detailed modeling
4+	256x+	Special needs

4.1.3 Edge Control Techniques

Edge Loops:

Ctrl + R  # Add an edge loop
# The closer the edge loops, the sharper the subdivision

# Create sharp edges
1. Add tight edge loops where sharpness is needed
2. Adjust the distance between edge loops to control sharpness
3. Use Ctrl + B (bevel) to create transitions

Creasing:

# Set crease
Shift + E  # Crease tool
Enter a value: 0 (no crease) to 1 (full crease)

# Use cases
- Maintain hard edges without adding geometry
- Partially sharpen edges
- Control subdivision behavior

4.2 Sculpt Mode

4.2.1 Sculpting Basics

Sculpt mode allows you to shape a model like using digital clay:

# Enter Sculpt Mode
1. Select the object
2. Switch to the Sculpting workspace
3. Or select Sculpting Mode from the mode menu

Sculpt Brush Types:

Brush	Function	Shortcut
Sculpt	Basic sculpting	X
Smooth	Smooth	S
Grab	Grab and move	G
Snake Hook	Hook and drag	K
Inflate	Inflate	I
Flatten	Flatten	Shift + T
Scrape	Scrape	Shift + T
Clay Strips	Clay strips	C

4.2.2 Dynamic Topology (Dyntopo)

# Enable Dynamic Topology
Ctrl + D  # Toggle Dynamic Topology

Dynamic Topology settings:
- Detail Size: Detail size (pixels)
- Relative Detail: Relative detail
- Detailing: Detail type
  - Subdivide Edges
  - Collapse Edges
  - Subdivide Collapse: Combined mode

Dynamic Topology Workflow:

# 1. Start with a simple mesh
Add a UV Sphere or Cube

# 2. Enable Dynamic Topology
Ctrl + D

# 3. Shape with sculpt brushes
- Push and pull basic shapes
- Add large form changes
- Gradually refine details

# 4. Adjust detail density
- High detail areas: Decrease Detail Size
- Low detail areas: Increase Detail Size

4.2.3 Multiresolution Sculpting

# Multiresolution modifier workflow
1. Add a Multiresolution modifier
2. Subdivide to create subdivision levels
3. Sculpt on different levels
4. Higher Levels: Detail sculpting
5. Lower Levels: Overall shape adjustment

Multiresolution advantages:
- Keep a low-poly model for animation
- High-poly for detail sculpting
- Can bake normal maps

4.3 Retopology Techniques

4.3.1 Importance of Retopology

Why retopology is needed:

• Meshes from sculpting have messy topology
• Animation requires a clean quad-based mesh
• Reduce polygon count to optimize performance
• Create a clear edge flow structure

4.3.2 Manual Retopology

# Manual retopology tools
1. Enable Snap to face
2. Create a new plane or use an existing mesh
3. Recreate the topology on the original model

Retopology tools:
- PolyBuild: Interactive polygon building
- Knife: Knife tool
- F: Fill face
- J: Join vertices

Retopology Best Practices:

# Edge flow direction guide
Muscle flow → Edge flow follows muscle texture
Joint areas → Ring-like edge flow for easy deformation
Around the eyes → Radial edge flow
Around the mouth → Ring-like edge flow around the lips

# Polygon count control
Game characters: 5,000-20,000 faces
Film characters: 50,000-200,000 faces
Real-time applications: As low polygon count as possible

4.3.3 Automatic Retopology

# Quad Remesh
Mesh → Remesh → Quad Remesh

Parameters:
- Octree Depth: Detail level
- Scale: Scale factor
- Sharpness: Sharpness
- Dual Mesh: Dual mesh

4.4 Boolean Operations

4.4.1 Boolean Operation Types

# Three boolean operation types
Union: A ∪ B - Merge two objects
Difference: A - B - Subtract B from A
Intersect: A ∩ B - Keep the overlapping part

4.4.2 Boolean Modifier

# Add Boolean modifier
Properties → Modifier Properties → Boolean

Parameter settings:
- Operation: Operation type
- Object: Target object
- Solver:
  - Fast: Fast (may have precision issues)
  - Exact: Precise (slower but accurate)

Boolean Operation Example:

# Make a slot in a screw head
1. Create a cylinder for the screw
2. Create a cube for the slot
3. Rotate the cube 45 degrees and adjust its size
4. Add a Boolean modifier to the screw
5. Operation: Difference
6. Object: The cube
7. Apply the modifier

4.4.3 Boolean Operation Best Practices

Boolean Operation Notes

• Ensure the mesh is manifold (closed)
• Avoid overlapping edges and faces
• Use the Exact solver for better results
• Check and fix the mesh after boolean operations

# Preparation before boolean operations
1. Check mesh integrity
   - Mesh → Clean up → Fill Holes
   - Mesh → Normals → Recalculate Outside

2. Ensure appropriate mesh density
   - Too dense: Slow operation
   - Too sparse: Detail loss

3. Use modifiers instead of applying directly
   - Maintain a non-destructive workflow
   - Can adjust parameters at any time

4.5 Hard-Surface Modeling

4.5.1 Hard-Surface Modeling Principles

Hard-surface modeling is used to create objects with clear boundaries, such as machinery, architecture, and products:

# Hard-surface modeling features
- Clear edges and corners
- Flat surfaces
- Regular geometric shapes
- Precise size control

4.5.2 Hard-Surface Modeling Techniques

Modifier Stack Combination:

# Typical hard-surface modifier stack
1. Mirror - Symmetrical modeling
2. Array - Repeating elements
3. Solidify - Add thickness
4. Bevel - Round edges
5. Subdivision Surface - Final smoothing

# The order of modifiers is important!

Modeling Techniques:

# 1. Start with the silhouette
Add a basic shape → Extrude the silhouette → Add details

# 2. Use precise measurements
Tab to enter precise numeric values
Enable snapping and increments

# 3. Maintain clean topology
Mainly use quads
Avoid n-gons and triangles

4.5.3 Mechanical Part Modeling Example

# Make a gear
1. Add a circle (24 vertices)
2. Enter Edit Mode, select all
3. Alt + E → Extrude Individual Faces
4. S → 0.8 (scale inwards)
5. E → Extrude teeth outwards
6. Ctrl + R to add an edge loop for the center hole
7. I → Inset to create the inner ring
8. Delete Faces → Delete the center
9. Add Subdivision and Bevel modifiers

4.6 Organic Modeling

4.6.1 Box Modeling Method

Start with a simple cube to create complex organic forms:

# Box modeling steps
1. Start with a cube
2. Use loop cuts to divide the main structure
3. Extrude to create limbs and appendages
4. Gradually refine the shape
5. Use proportional editing to smooth transitions
6. Add a Subdivision Surface modifier

4.6.2 Organic Modeling Techniques

Form Control:

# Proportional Editing
O  # Enable proportional editing
Scroll wheel # Adjust influence range
Alt + O # Toggle connected mode

# Smooth Tool
Alt + S # Scale along normal (inflate/deflate)
Shift + Alt + S # Smooth scale along normal

Modeling with Muscle Flow:

# Follow anatomical structure
1. Study real anatomical references
2. Edge flow follows muscle texture
3. Focus on joints and deformation areas
4. Maintain symmetry (use a Mirror modifier)

4.7 Practical Exercises

Exercise 1: Coffee Cup Modeling (Subdivision Surface)

Exercise Goal

Master the basic workflow and edge control of subdivision surface modeling

# Make a coffee cup using subdivision surface
# Step 1: Create the cup body silhouette
1. Delete the default cube
2. Shift + A → Mesh → Cylinder (Vertices: 12)
3. Tab to enter Edit Mode
4. Select the top face, Delete → Faces (create an opening)

# Step 2: Shape the cup body
5. 2 → Switch to edge select mode
6. Alt + Left-click to select edge loops at different heights
7. S → Scale different edge loops to create the cup silhouette
8. Select the opening edge loop, E → Extrude inwards to create the cup rim thickness

# Step 3: Add subdivision
9. Add a Subdivision Surface modifier (Level: 2)
10. Add edge loops where sharpness is needed (Ctrl + R)
11. Adjust edge loop positions to control curvature

# Step 4: Make the handle
12. Select two faces on the side of the cup
13. E → Extrude, S → 0 to merge
14. E → Continue extruding to form the handle shape
15. Use G and R to adjust the handle's curve

Exercise 2: Simple Character Head (Sculpting)

# Create a character head using sculpt mode
# Step 1: Prepare the base model
1. Add a UV sphere
2. Switch to the Sculpting workspace
3. Ctrl + D to enable Dynamic Topology

# Step 2: Shape the basic head form
4. Use the Grab brush (G) to adjust head proportions
5. Use Snake Hook (K) to pull out the nose
6. Inflate (I) to thicken the lip area
7. Use the Grab brush to adjust the depth of the eye sockets

# Step 3: Add details
8. Decrease Detail Size to increase detail density
9. Use Clay Strips to add muscle texture
10. Use the Smooth brush (S) to smooth transition areas
11. Use the standard sculpt brush to add wrinkles and other details

# Step 4: Finalize and optimize
12. Retopologize using Quad Remesh
13. Manually adjust key edge flows
14. Add a Subdivision Surface modifier

Exercise 3: Mechanical Part (Hard-Surface + Boolean)

Important Notes

• Hard-surface modeling requires precise measurements and symmetry
• Ensure mesh integrity for boolean operations
• Use the modifier stack order appropriately

# Make a bolt and nut combination
# Bolt creation:
1. Add a cylinder (12 vertices)
2. S → X/Y → 0.5 to shrink the diameter
3. S → Z → 3 to elongate
4. Select the top face, E → Extrude the bolt head
5. S → 1.5 to enlarge the bolt head

# Thread creation:
6. Add another cylinder for the thread
7. Add a Screw modifier
8. Adjust parameters to create the thread effect
9. Use a Boolean modifier to merge with the bolt

# Nut creation:
10. Add a cylinder
11. In Edit Mode, select 6 faces to create a hexagon
12. I → Inset to create the inner hole
13. Delete Faces to delete the center
14. Use a Boolean modifier to cut the thread hole

# Assembly and rendering:
15. Insert the bolt into the nut
16. Add a metal material
17. Set up appropriate lighting
18. Render the final effect

4.8 Advanced Modeling Tools

4.8.1 Extra Objects Add-on

# Enable Extra Objects add-on
Edit → Preferences → Add-ons → Extra Objects

New object types:
- Extra Meshes: More basic meshes
- BoltFactory: Bolt generator
- ANT Landscape: Landscape generator
- Discombobulator: Random detail generator

4.8.2 Loop Tools Add-on

# Loop Tools functions
- Bridge: Bridge edge loops
- Loft: Loft connections
- Relax: Relax vertices
- Space: Distribute evenly
- Curve: Curve edge loop
- Circle: Circle selection
- Flatten: Flatten

4.8.3 F2 Add-on

# F2 quick fill
F  # Smart fill face
- Automatically detects the best fill method
- Supports quads and triangles
- Improves modeling efficiency

Advanced Modeling Shortcut Summary

Tool	Shortcut	Description
Toggle Subdivision Surface	Ctrl + 1-6	Quickly set subdivision level
Sculpt Mode	Ctrl + Tab	Switch to sculpt mode
Dynamic Topology	Ctrl + D	Toggle dynamic topology
Crease	Shift + E	Set edge crease
Mark Sharp	Shift + Ctrl + E	Mark sharp edge
Sculpt Brush Size	F	Adjust brush size
Sculpt Brush Strength	Shift + F	Adjust brush strength
Smooth Sculpt	Shift + Mouse	Temporarily switch to smooth brush
Subtract Sculpt	Ctrl + Mouse	Reverse sculpt effect

4.9 Modeling Workflow Optimization

4.9.1 Non-Destructive Modeling

# Modeling workflow suggestions
1. Use modifiers instead of direct operations
2. Keep the original mesh simple
3. Apply modifiers in stages
4. Back up important nodes regularly

# Modifier stack management
- Mirror at the bottom (affects all subsequent modifiers)
- Subdivision at the top (applies smoothing last)
- Boolean in an appropriate middle position
- Can adjust order and parameters at any time

4.9.2 Performance Optimization

# Improve modeling performance
1. Set subdivision levels reasonably
   - Use low levels for editing
   - Use high levels for rendering

2. Use simplified display
   - Edit in wireframe mode
   - Hide unnecessary objects
   - Use hierarchy management

3. Clean up the scene regularly
   - Delete unused meshes
   - Merge similar objects
   - Apply modifiers that are no longer needed

Learning Suggestions

1. Progressive Learning: Start with simple shapes and gradually increase complexity
2. Practice-Oriented: Do many practice projects, combining theory with practice
3. Reference Learning: Observe the forms and structures of real objects
4. Tool Proficiency: Master the shortcuts for various modeling tools
5. Be Patient: Complex modeling requires time and experience to accumulate

By completing this chapter, you should be able to:

• Use subdivision surfaces for organic modeling proficiently
• Master sculpting tools to create complex details
• Understand and apply retopology techniques
• Use boolean operations for complex modeling
• Be capable of hard-surface and organic modeling

These advanced modeling techniques are key skills for creating professional-grade 3D models and require a lot of practice to master.