Blender

Transforms

1. Apply scale before export — Ctrl+A → Scale, or objects deform in game engines
2. Apply rotation for correct orientation — especially for rigged models
3. Non-uniform scale breaks modifiers — apply scale before Mirror, Bevel, etc.
4. Reset transforms: Alt+G/R/S — location, rotation, scale to defaults

Object vs Edit Mode

1. Object mode transforms affect whole object — Edit mode transforms geometry only
2. Modifiers applied in Object mode — Edit mode shows base mesh
3. Selection works differently — Object selects whole, Edit selects vertices/edges/faces
4. Tab to toggle — most operations mode-specific

Normals

1. Flipped normals = invisible faces — Shift+N to recalculate outside
2. Check in Viewport Overlays → Face Orientation — blue is correct, red is flipped
3. Ctrl+Shift+N for flip inside — useful for interior scenes
4. Smooth shading issues = bad normals — recalculate first

Modifiers

1. Order matters — Mirror before Subdivision, Bevel before Mirror typically
2. Apply modifiers for export — game engines don't understand Blender modifiers
3. Array + Curve = deformation issues — apply Array first, then Curve
4. Subdivision preview vs render levels — set same for consistent export

UV Unwrapping

1. Mark seams where texture can split — Ctrl+E → Mark Seam
2. Seams at hidden areas — under arms, behind ears, model edges
3. U → Unwrap after marking — Smart UV Project as fallback
4. Check UV overlap — causes baking issues, separate islands

Origin Point

1. Origin affects rotation/scale pivot — Right-click → Set Origin
2. Origin to geometry for centered pivot — Origin to 3D Cursor for precise placement
3. Origin matters for game engine import — often should be at feet/base

Export for Game Engines

1. FBX or glTF for Unity/Unreal — glTF for web
2. Apply transforms on export — "Apply Scalings: FBX All" for Unity
3. Forward axis: -Z Forward, Up: Y Up for Unity — different for Unreal
4. Embed textures or pack separately — depends on workflow

Python API (bpy)

1. bpy.context is current state — selection, active object, mode
2. bpy.data is all data — access any object by name regardless of selection
3. bpy.ops are operators — require correct context (mode, selection)
4. Override context for operators — {'object': obj, 'selected_objects': [obj]}
5. Most ops need Object mode — bpy.ops.object.mode_set(mode='OBJECT') first

Common Mistakes

1. Duplicate with Alt+D creates linked copy — changes affect both, use Shift+D for independent
2. Delete vs Dissolve — Delete removes geometry, Dissolve merges (Edit mode)
3. Proportional editing left on — affects unexpected vertices, check header
4. Subdivision on high-poly crashes — start with Levels: 1, increase gradually
5. Materials not linked to object — won't export, must be assigned to faces