version: "1.0.0" name: blender-modeling last_reviewed: 2026-09-06 group: 3D assets description: >- Model, retopologise, UV unwrap and bake game-ready assets with correct scale, pivots and polycount. Use when creating 3D hard-surface meshes, low-poly props, or UV layouts.

blender-modeling

Core Philosophy

3D modeling for real-time video games is not creating unconstrained digital sculptures. A high-poly model with 4,000,000 polygons and 12 un-optimized material slots will crash a game engine. Real-time 3D art is the rigorous craft of geometric efficiency: sculpting high-fidelity details, retopologizing into clean low-poly game meshes, baking high-to-low normal maps with zero shading artifacts, establishing consistent texel density, and enforcing strict transform hygiene.

4-Step Game-Ready 3D Modeling Pipeline

Step 1: High-Poly to Low-Poly Modeling & Retopology

1. High-Poly Sculpting / Hard-Surface:

• Model complete micro-details: bevels, screws, seams, welded joints, cloth folds.

1. Low-Poly Retopology Discipline:

• Silhouette is King: Allocate polygon budget to the outer silhouette where curved edges meet the sky/background. Flat surfaces require minimal geometry.
• Clean Edge Loops: Quad-dominant topology along deformation joints; triangulate flat surfaces before export to prevent engine-specific triangulation warping.
• Polycount Budgets:
• Hero Character: 30k–60k triangles.
• First-Person Weapon: 15k–30k triangles.
• Environment Prop: 1k–5k triangles.

Step 2: UV Unwrapping & Texel Density Standardization

1. The Texel Density Constant:

• Standardize pixel density per meter across all assets in the game world:
• Hero First-Person Props: 2048 px/m (4K texture for 2m object).
• Standard Characters / Weapons: 1024 px/m (2K texture for 2m object).
• Environment Props / Architecture: 512 px/m.

1. UV Seam Placement & Packing Hygiene:

• Place UV seams in concealed areas (undersides, inner seams, sharp mechanical angles).
• Packing Efficiency: Achieve $\ge 75\%$ UV space utilization. Pack UV islands with at least 16px padding (at 2K resolution) to prevent mipmap texture bleeding.

Step 3: Normal Map Baking & Shading Seam Prevention

1. The 3 Golden Rules of Baking:

• Rule 1: Hard Edges Require UV Seams: Any sharp edge ($> 60^\circ$ angle) marked with a Hard/Sharp Edge must have a corresponding UV seam split to prevent dark shading gradients across normal maps.
• Rule 2: Triangulate Before Baking: Triangulate the low-poly mesh prior to baking to guarantee the normal map is baked against the exact triangulation the engine renders.
• Rule 3: Use Average Normals & Cage: Use an expanded cage mesh to prevent projection ray intersection clipping on tight mechanical crevices.

Step 4: Transform Hygiene & Export Configuration

1. Transform Normalization:

• Apply all transforms: Location (0,0,0), Rotation (0,0,0), Scale (1.0, 1.0, 1.0).
• Set Origin Point: Place the origin pivot at the logical physical base (e.g. bottom-center of props for easy ground snapping, or center-of-mass for physics debris).

Deliverable Format: 3D Asset Specification (ASSET-SPEC.md)

# Real-Time 3D Asset Specification: [Prop Name]
 
## 1. Geometric Budget & Dimensions
-**Asset Name**: Tactical First-Aid Station Prop
-**Physical Dimensions**: 0.6m (W) x 0.8m (H) x 0.25m (D)
-**Target Polygon Count**: 3,200 triangles (Budget: <= 4,000 triangles)
-**Topology**: 100% clean manifold geometry; zero ngons; zero loose vertices.
 
## 2. UV & Texel Density Standards
-**Texture Set Size**: 2048x2048px (PBR Metallic/Roughness workflow)
-**Target Texel Density**: 1024 px/meter
-**UV Island Padding**: 16px minimum gutter spacing
-**UV Space Efficiency**: 79.4% packed area
 
## 3. Texture Map Manifest
| Map Type | Channel Packing | Format | Bit Depth |
|---|---|---|---|
| Base Color / Albedo | RGB | PNG / TGA | 8-bit sRGB |
| Normal Map | RGB (OpenGL / DirectX) | PNG / TGA | 16-bit Linear |
| ORM Map | R: Occlusion, G: Roughness, B: Metallic | PNG / TGA | 8-bit Linear |
 
## 4. Transform & Pivot Setup
-Pivot Point: Bottom-center at `(0, 0, 0)`.
-Applied Scale: `(1.0, 1.0, 1.0)` confirmed.

Worked Example: Eliminating Black Normal Map Seams

• Problem: Hard-surface weapon model exhibited ugly dark shading gradients along mechanical edges when imported into Unreal Engine.
• Diagnosis: 90-degree bevel edges were marked as smooth without UV seams, forcing the normal map to compensate for extreme vertex normal bending.
• Fix: Marked 90-degree edges as Sharp; split UV islands along those exact edges; re-baked with cage.
• Result: Shading rendered completely seamless and flat under real-time lighting.

Verification Checklist

• [ ] All transforms applied (Scale is strictly 1.0; rotation is 0,0,0).
• [ ] Pivot origin positioned at logical attachment/ground point.
• [ ] No ngons (faces with $> 4$ vertices) or non-manifold geometry present.
• [ ] Texel density verified consistent with project standards.
• [ ] Hard/sharp edges correspond 1:1 with UV seam boundaries.

Anti-Patterns

• Leaving Unapplied Scales: Exporting an asset scaled at 0.05, breaking real-time physics and distance culling.
• Wasted UV Texture Space: Packing UVs with 40% empty white space, wasting texture VRAM.
• Baking Without UV Padding: Setting 0px gutter margin between UV islands, causing colors to bleed across LOD mipmaps.