10(a) 3D Modeling for Games - California State …athena.ecs.csus.edu/~gordonvs/165/resources/10a-Modeling.pdf · Computer Game Architecture 10(a) – 3D Modeling for Games CSc 165

CSc 165

Computer Game Architecture

10(a) – 3D Modeling

for Games

CSc 165 Lecture Note Slides

10a - 3D Modeling For Games

2

Overview

• Model Characteristics

• 3D Model File Formats

• Model Loaders

• Digital Content Creation (DCC) Tools

• Skinning and UV-unwrapping



3

Models



4

Static Data o 3D geometry (vertex data)

o Polygon (face) data

o Rendering attributes o Wireframe / Faceted / Smooth-shaded

o Lighting & Materials

o Texturing (“skinning”) data

Animation Data (sometimes) o Model structure (skeletons, joints)

o Model poses

o Animation sequences o walk / run / jump / die …



5

Common 3D Model File Formats

.3ds – 3D Studio Max format

.blend – Blender format

.dae – COLLADA Digital Asset Exchange format

.dem – USGS Standard for Digital Elevation Models

.dxf – Autodesk's AutoCAD format

.hdf – Hierarchical Data Format

.iges – Initial Graphics Exchange Specification

.iv – Open Inventor File Format Info

.lwlo, .lwob & .lwsc – Lightwave 3D file formats

.md2/.md3/.md4/.md5 – Quake Model Files

.ms3d – Milkshape 3D binary format



6

.msdl – Manchester Scene Description Language

.nff & .enff – (Extended) Neutral File Format

.obj – Alias|Wavefront Object Files

.off – 3D mesh Object File Format

.oogl – Object Oriented Graphics Library

.ply – Stanford Scanning Repository format

.pov – Persistence of Vision ray-tracer

.qd3d – Apple's QuickDraw 3D metafile format

.viz – used by Division's dVS/dVISE

.vrml – Virtual Reality Modeling Language

.x – Microsoft’s DirectX/Direct3D file format

.x3d – eXtensible 3D XML-based scene description format

See wikipedia – list of file formats



7

.OBJ File Commands

Vertex data o v – geometric data

o vt – texture data

o vn – vertex normals

Elements o p – point

o l – line

o f – face

o curv – curve

o surf – surface

Grouping o g – group name

o s – smoothing group

o mg – merging group

o o – object name

Render Attributes o usemtl – material name

o mtllib – material file name

o lod – level of detail

o shadow_obj – shadow casting



8

.OBJ Example # File: ‘cube.obj’

# This file uses “OBJ” format to define a cube which has a

# different “material” applied to each of its faces.

# Define 8 cube vertices

v -1.0 -1.0 -1.0

v -1.0 -1.0 1.0

v -1.0 1.0 -1.0

v -1.0 1.0 1.0

v 1.0 -1.0 -1.0

v 1.0 -1.0 1.0

v 1.0 1.0 -1.0

v 1.0 1.0 1.0

# Specify the file (library) containing materials

mtllib cube.mtl

#continued...



9

.OBJ Example (cont.)

# file ‘cube.obj’ (cont.)

# Define a group (g) and material for each face (f)

g front

usemtl red

f 2 6 8 4

g back

usemtl blue

f 1 3 7 5

g right

usemtl green

f 6 5 7 8

g top

usemtl yellow

f 4 8 7 3

g left

usemtl magenta

f 2 4 3 1

g bottom

usemtl cyan

f 2 1 5 6

#end of ‘cube.obj’



10

OBJ Face/Vertex Data Structures

Vertices Faces

1 x y z

2 x y z

3 x y z

4 x y z

5 x y z

6 x y z

. . .

1

V1

V2

V3

2 V1

V2

V3

3

V1

V4

# File ‘man.obj’

v -1.0 -1.0 -1.0

v -1.0 -1.0 1.0

v -1.0 1.0 -1.0

...

vt 0.72 0.32

vt 0.86 0.33

...

vn 1.0 0.0 1.0

vn -1.0 0.0 0.5

...

f 2/1/1 4/2/1 3/3/2

f 1/4/2 2/4/2 5/5/3

...

V4



11

Content Loaders in RAGE

Model

File

Read

Create

Insert

Scenegraph Object in some

specific file format

Format-specific

loader code

<<interface>>

MeshLoader

GenericEntity

WavefrontMeshLoader

+ loadAsset(fileName)

+ loadAsset(fileName)

<<interface>>

Entity

GenericSubEntity

- vertexBuffer

- TexCoordBuffer

- NormalsBuffer

<<interface>>

SubEntity



12

Example: .OBJ Content Loader

public class WavefrontMeshLoader implements MeshLoader

{ ...

public void loadAsset(Mesh mesh, Path path)

{ List<Float> verts = new ArrayList<>();

List<Float> norms = new ArrayList<>();

List<Float> texcoords = new ArrayList<>();

BufferedReader br = Files.newBufferedReader(path);

String line;

while ((line = br.readLine()) != null)

{ if (line.startsWith(VERTEX_COMMAND))

{ processVertexPositionCommand(line, verts); }

else if (line.startsWith(TEXTURE_COORD_COMMAND))

{ processVertexTextureCommand(line, texcoords); }

else if (line.startsWith(NORMAL_COMMAND))

{ processVertexNormalCommand(line, norms); }

else if (line.startsWith(FACE_COMMAND))

{ processVertexFaceCommand(line); }

else if (line.startsWith(MATERIAL_COMMAND))

{ materialLib = line.split(" ")[1]; }

}

SubMesh sm = mesh.createSubMesh(mesh.getName());

createVertexBuffers(verts, norms, texcoords);

sm.setVertexBuffer(toFloatBuffer(vertexPositionsList));

sm.setNormalBuffer(toFloatBuffer(vertexNormalsList));

sm.setTextureCoordBuffer(toFloatBuffer(vertexTexCoordsList));

sm.setIndexBuffer(toIntBuffer(vertexIndicesList)); } ...



13

Digital Content Creation (DCC) Tools

Too much work to do “by hand”

Model

File

Content

Loader Entity

Scenegraph

DCC

Tool

Model

File

Model

File

Model in Content-Loader format

Model in different format 1

Model in different format 2

commands

“Export”

“Import”



14

DCC Tools

Commercial o Maya

o 3DStudio Max

o Lightwave

o etc., etc. …

Free (or nearly) o Blender

o MilkShape3D

o Maya / 3DStudio Max for students

o etc. …



15

Blender Features:

Modeling, texturing, lighting, UV-mapping

Animation rigging/skinning

Particle, physics, soft-body, fluid & cloth simulations

Game engine, video post-processing

Python scripting/plugin support

Cross-platform (Windows, Linux, Mac OSX, FreeBSD, Solaris….)

Import/export for a wide variety of model file formats

Extensive online documentation/wiki support

Availability: Free (GNU GPL license), at http://www.blender.org

Tutorials: http://www.blender.org/support/tutorials



Example Blender Models

16



Basic Blender Controls

Viewing:

• Scroll-wheel: zoom

• MMB: orbit (rotate 3D view)

• Shift-MMB: pan

• Reset view to Top: NUM-7 Front: NUM-1 Side: NUM-3

• Z-key: toggle wireframe

• NUM-0: switch to camera view

• NUM-5: toggle ortho/perspective view

• HOME: set view to show all objects

• Ctrl-Z: undo

• Ctrl-S: save workspace

• Ctrl-N: reset (discard all; new session)

• F12: render

17

Object Manipulation (in object mode):

• RMB: select (SHIFT to add)

• A-key: toggle select-All

• B-key: activate border-selection

(rubber-band select)

• DEL-key: delete selected

• LMB: position 3D cursor

• Shift-A: add object (at cursor loc)

• Transform selection:

R-key: rotate S-key: scale G-key: grab

LMB to accept; RMB or ESC to cancel

• Quick move: RMB on object, drag,

LMB to drop

• Shift-D: duplicate selection

(drag to reposition)

• TAB: toggle object/edit mode



18

Building Models From Primitives

Extrude Multiple Extrusions

Scale Ends

Original Cube

Scale Inner

Surfaces

Add Bevels

and Smooth Model concept: The Essential Blender,

Roland Hess, Blender Foundation



Model Exporting

Most DCC tools export a variety of formats Blender supports exporting to:

o Collada XML (“.dae”)

o Wavefront OBJ (“.obj”)

o Stanford Graphics Library (“.ply”)

o 3DStudio Max (“.3ds”)

o A host of others via “addons”

Including “OgreXML”

RAGE has ModelLoaders for o OBJ

o RAGE Skeletal Animation (custom Blender exporter) 19



Exporting Models

20

# Blender3D v249 OBJ File:

CrossDemo.blend

# www.blender3d.org

mtllib CrossDemo.mtl

v 0.515410 2.745096 -0.496360

v 0.515410 2.745096 0.496359

v -0.477309 2.745096 0.496359

v -0.477309 2.745096 -0.496360

v 0.515410 3.737815 -0.496359

v 0.515410 3.737815 0.496360

v -0.477309 3.737815 0.496359

v -0.477309 3.737815 -0.496360

v -0.523100 6.135959 0.542150

v -0.523100 6.135958 -0.542150

v 0.561200 6.135959 0.542150

v 0.561201 6.135958 -0.542150

...#total 44 vertices

usemtl Material

s 1

f 2 6 7

f 5 1 4

f 12 10 9

f 13 14 15

f 1 42 44

f 21 24 44

...#total 42 faces

Export:

Ogre

OBJ

DAE



Advanced Modeling: Sculpting

21

“Grab” brush

“Layer” brush “Inflate” brush

“Add” brush

applied to Sphere

“Texture” brush

Images from: The Essential Blender,

Roland Hess, Blender Foundation

Original sphere



22

Skinning

Applying “texture” to 3D models

Problem: texture mapping is per-polygon: Models are collections of polygons

u

v

Texture Map

(1,1)

(0,0)

Polygon



23

Texture Space Subdivision

Texturing meshes by dividing texture space:

u

v

Texture Map

Polygon Mesh



24

Skinning Example

Image credit: Practical Java Game Programming,

Clingman et.al., Charles River Media



25

Texture Subdivision Difficulties

Requires creating a complex mapping (and the model is often curved)

How do we create the texture map?

How do we determine the correct mapping?

Mapping texture locations

to model coordinates

Image credit: Practical Java Game Programming,

Clingman et.al., Charles River Media



26

Creating Texture Skins

Create the model

Flatten the model (“UV Unwrapping”) Mark seams

Cut along seams (“project”)

Save unwrapped (flattened) UV image

Save model with texture coordinates

Use UV image as a “pattern” to create tex map GIMP, PhotoShop, ...

Apply texture map to model



27

Example: Soup Can

Soup Can Model

(Cylinder)

Texture

Mapping

Image credit: 3D Game Programming All In One,

Kenneth Finney, Premier Press

Unwrap

Create

Texture

Image

GIMP, PhotoShop, …

Texture Image Model with Texture Coords



Blender UV Unwrapping

28



29

Character Models

More complex, but same approach:

Create model

Mark/cut seams (some tools support groups)

Project UV’s

Save projection image

Use projection image to create texture

Apply texture to UV map/model



Blender: Character Example

30 Example from: 3D Game Programming All In One,

Kenneth Finney, Premier Press

Step 1: Load/Create Model



31

Step 2: Mark Seams



32

Step 3: Export UVs



33

Step 4: Paint Texture

GIMP,

PhotoShop,

MS Paint,

etc.



34

Step 5: Apply Texture to Model

Documents

10(a) 3D Modeling for Games - California State …athena.ecs.csus.edu/~gordonvs/165/resources/10a-Modeling.pdf · Computer Game Architecture 10(a) – 3D Modeling for Games CSc 165