Creating 3d Assets for GamesC. Morris - 2013

Creating 3d Assets for Games

What is an asset.

Any piece of digital media used within a title. This includes:

• Textures

• Materials

• Meshes

• Sounds

• Music

• Animations

• Sprites

• etc ...

We will be focusing on the first three; Textures, Materials and Meshes.

Creating 3d Assets for Games

Textures

Creating 3d Assets for Games

Textures overview.

• Textures add detail and context to geometry without changing or adding to it.

• They are however limited in scope.

• Used in more complex material systems to provide more control over how a surface appears.

Creating 3d Assets for Games

Texture variables.

Use & Context – Helps define other variables:

• Consider where the texture is going to be used. On what kind of surface.

• Textures for complex meshes should be approached differently to those for simple geometry.

• Matching game aesthetics.

Creating 3d Assets for Games

Resolution – The size of a texture:

• Textures are measured in pixels, normally base 2 , frequently square.

• Dependent on use, must not only fit aesthetic but be related to physical size of mesh it is used on.

• Larger meshes often need larger textures to maintain level of detail.

• Most engines will accept textures as high as 4096x 4096, some will take higher. Standard texture size however ranges between 512 and 2048.

Creating 3d Assets for Games

Tiling – Does the texture smoothly repeat:

• Textures used on large, uncomplicated geometry are often tiled.

• Tiling is often more efficient as a smaller texture can cover a larger area.

• Texture seams should be contiguous to hide where texture repeats.

• Small areas with a defined shape should be minimised.

• Can result in a less detailed textures, as overly detailed textures can make tiling very obvious.

• Purposefully repeating patterns (such as tiles) can be tiled well as long as each tile is simple.

Creating 3d Assets for Games

Tiling examples.

Non tiling concrete texture Tiling concrete texture

Creating 3d Assets for Games

Colour – Does the texture incorporate colour:

• Depending on use some textures work best in monochrome in order to be coloured later.

• Textures can be used in materials (see later) to create effects modulated via colour.

• Monochrome textures do not need to be saved in a colour format, and therefore require less memory.

Creating 3d Assets for Games

Alpha – Extra data contained within texture files:

• Certain file types save an extra channel known as alpha.

• This extra channel can be used to convey more data in single file.

• Often used to store transparency, or other maps used in materials.

• Files containing alpha channels tend to be larger, but often are smaller than saving another file to convey the information.

Creating 3d Assets for Games

Materials

Creating 3d Assets for Games

Materials overview.

• Used to create a more in-depth and detailed representation of a surface.

• Based on shaders, also known as lighting models. Define how light is calculated when it interacts with the surface.

• Affects how a surface is rendered on a pixel by pixel level.

• Use a mixture of different textures and mathematical functions to achieve desired effect.

• Almost entirely replaced textures in modern engines (I.E. You can no longer place a simple texture on a surface, it must be inside a material).

Creating 3d Assets for Games

Texture maps – Used in combination with shaders to create desired effect:

• Defuse – Imparts colour, shade, tone, contrast.

• Specular – Details areas of high reflectance and shine.

• Normal – Fakes details, such as bumps and dents by modifying the angles used in calculating light reflectance, without adding detail to the model.

• Masks – Maps used to partition areas to allow for differing effects across the surface.

• Bump – Modifies the appearance of the surface by displacing it in 3d space. Normal mapping is a form of bump mapping.

• Baked lighting – Extra maps used to impart more shade and tone relevant to environmental conditions. E.g. Ambient Occlusion and Cavity maps.

Creating 3d Assets for Games

Texture maps example.

Defuse Normal Specular

Creating 3d Assets for Games

Normal and Bump mapping (detailed):

• Giving depth to a material without adding extra geometry.

• Shader displaces surface in 3d space on a per pixel basis according to texture map it is provided with.

• Bump maps are normally monochrome maps used to convey height variation.

• Normal maps are full colour maps used to alter the calculated orientation (or normal) of each pixel on a face.

• This method allows for a high level of detail to be displayed on a low resolution model.

Creating 3d Assets for Games

Normal and Bump map example.

Defuse Defuse + Normal Defuse + Normal + Bump (displacement)

Creating 3d Assets for Games

Meshes

Creating 3d Assets for Games

Meshes Basics.

• Meshes are made up of Vertices, Edges, Faces (or polygons), and Surfaces.

• The orientation of any element is known as a normal.

• Most renderers only render the front of faces and not the reverse.

• Normals are used by the shader to smooth the surface.

• Polygons are not limited to a set number of edges. However most engines will only work with Triangular or Quadrilateral polygons.

Creating 3d Assets for Games

UV maps – Translates between 3d space and 2d space:

• Required to correctly place a texture onto a mesh.

• A 2d coordinate system (UVW) similar to 3d space (XYZ).

• Process saves 3d faces onto a 2d map. Similar to creating a world map, making an item of clothing, or peeling an orange.

• This UV map can then be used as a basis to create textures as the artist knows where the texture will appear on the model.

Creating 3d Assets for Games

UV map examples.Base model

Final textured model

UV map layout

Final defuse texture

Creating 3d Assets for Games

Texture baking – Creating textures directly from a mesh:

• Requires a high resolution model, and a low resolution model which will be used in the game engine.

• Lighting effects are applied to the high resolution model, then “projected” onto the game model.

• These lighting effects are then saved using the UV map of the game model.

• Detail from high resolution model now “baked” onto game model.

• Can be used to create many textures from defuse to normal and bump maps.

• Very common workflow uses zBrush to create high resolution models.

Creating 3d Assets for Games

Texture baking example.

Creating 3d Assets for Games

Tools & Pipelines

Creating 3d Assets for Games

Suggested tools :

• Image editor – Creating and editing textures. Photoshop in particular has lots of useful tools including a high degree of brush control, colour control, channels access and an inbuilt library of file type exporters.

• 3d modding application – Creating meshes. 3dmax, Maya, and Blender are all good options

• Digital sculpting application – Creating high resolution models for texture baking. zBrush is the preferred option, but can be difficult to use. Mudbox is a reasonable alternative

• nDo2 – A Photoshop plug-in which is extremely useful in creating complex textures all from within Photoshop. Including creating normal maps from scratch and converting them into other map types such as defuse and specular.

Creating 3d Assets for Games

Pipelines – The process of importing assets into a game environment:

• Engines have specific requirements for models and textures.

• Research the engine you are using to find the required settings.

• Options to look out for:

• Meshes – Texture coordinates (UV maps), smoothing groups, materials and animations. Y/Z axis orientation.

• Textures – Bit depth, colour, and compression.

• Suggested File types:

• Meshes – FBX, OBJ

• Textures – TGA, PNG, BMP

Creating 3d Assets for Games

Example UDK pipeline