Introduction to Materials

Contents

• Materials• Editing materials• Quick methods for editing materials in UDK

Introduction to Materials

• Materials affect the appearances of games• Let objects appear to be what they should

look like

What are Materials ?

• Simple approach: the pigment r of a surface• pigment controls colors• Materials make the surface apear to be

something what they should look like

Material vs Texture

• Texture is an image• Materials contains textures and more, for

example, transparency, emittance and etc.

Texture UV Coordinates

• A texture is defined a two-dimensional space• We have to map the 2D texture to the surface

of an object in three-dimensional space

Texture UV Coordinates

• Horzontal axis : U-axis• Vertical axis : V-axis • Sometimes, the texture coordinate is called

the tangent space 。• Each vertex should be assoicated with a

texture coordinates

Example

Source:http://en.wikipedia.org/wiki/File:UVMapping.png

U Direction

V Direction

1.0

1.0

0, 0

Example

• Cube Representative UV

Source : http://en.wikipedia.org/wiki/File:Cube_Representative_UV_Unwrapping.png

  A representation of the UV mapping of a cube. The flattened cube net may then be textured to texture the cube

• Set instructions to compute the appearance of a material

• There are default values for each instruction for simulating the the lit surface

• Remember to turn on light in order to see the materials.

Material Components

• Components:• Material Nodes ( 材质节点 )• Basic components• Material Channels ( 材质通道 )• Set the specific properties of a material

• 材质表达式（ Material Expressions ）。• A building block for creating materials. • Each expression defines a specific function, for example,

connecting textures, adding two values, vectors or modify coordinates of textures.

Material Components

Material Nodes

Material Channels

Material Expressions

Example: Creation of a Material

• 1. Run UnrealEd• 2. Open Generic browser• 3. File - > New• 文件包（ Package） : MyFirstGameLevel• 组 (Group): Materials • 名称 (Name): mat_test_01 • 组件工厂 (Factory): Material

Double click the new material, you will see the following:Left hand side: the appearance of the materialA material node represent the new material

Material Channels

• Diffuse ( 漫射 )• Emissive （自发光）• Specular （高光）• Specular Power （高光次幂）• Opacity （不透明）• Opacity Mask （不透明蒙板）• Distortion （扭曲）• Transmission Mask/Transmission Color （透射蒙板 / 透射

色） • Normal （法线） • Custom Lighting （自定义光照）

Show demo for the following items

• Diffuse ( 漫射 )• Emissive （自发光）• Specular （高光）• Specular Power （高光次

幂）

Diffuse

Emissive

Opacity （不透明）

-Set“LightingModel” （光照模型） as MLM_Unlit

- Set BlendMode” （混合模式） as BLEND_Masked 、 BLEND_Translucent 、BLEND_Additive 或 BLEND_Modulate

BLEND_OPAQUE

BLEND_Translucent

Opacity Mask （不透明蒙板）

A simplified version of the opacity.Can be used if MLM_Phong is not available.

It’s value boolean map. 1 for on0 for offIf the pixel value is smaller than a clipping value, it’s computed value is 0; otherwise it is 1.

Opacity Mask （不透明蒙板）

BLEND_MODE = BLEND_Masked

Distortion （扭曲） Model refraction effect

Used when MLM_Unlit is used.

http://upload.wikimedia.org/wikipedia/en/e/eb/Rays_incident_on_medium.png

Transmission Mask/Transmission Color

- Model sub-surface scattering （次表面散射）

-Subsurface scattering (or SSS) : a mechanism of light transport in which light penetrates the surface of a translucent object, is scattered by interacting with the material, and exits the surface at a different point.

Source: wikipedia

Subsurface scattering

http://en.wikipedia.org/wiki/File:Subsurface_scattering.png

Normal Map or "Dot3 bump mapping", is a technique used for faking the lighting of bumps and dents. It is used to add details without using more polygons. A normal map is usually an RGB image that corresponds to the X, Y, and Z coordinates of a surface normal from a more detailed version of the object.

Normal map

Normal Map

WithoutNormal Map

Transmission + Normal

BLEND_Translucent

Custom Lighting （自定义光照）

Define your own lighting function

You must enable this channel by setting lighting model as MLM_Custom

Custom Lighting

Material Expressions– Abs （求绝对值）– Add （加法）– AppendVector （向量合并）– BumpOffset （凹凸偏移）– CameraVector （相机位向量）– Ceil （值上限取整）– Clamp （区间值限定）– ComponentMask （分量蒙板）– 常量表达式

» Constant （常量）» Constant2Vector （二维常数向量）» Constant3Vector （三维常数向量）» Constant4Vector （四维常数向量）

Desaturation （冲淡颜色）DestColor （目标色）DestDepth （目标深度）Divide （除法）DotProduct （点乘、内积 )Cosine （余弦）CrossProduct （叉乘、外积）DepthBiasedAlpha （深度偏移 Alpha ） DepthBiasedBlend （深度偏移混合）

Material Expressions

FlipBookSample （翻书采样）Floor （值下限取整） Frac （取小数值）Fresnel （菲涅尔）If （条件表达式）LightVector （光照向量）LinearInterpolate （线性插值）

Material Expressions

MeshEmitterVertexColor （网格物体发射器顶点色） MeshSubUV （网格物体子 UV ） Multiply （乘法表达式） Normalize （单位化）OneMinus （一减去）Panner （平移器）ParticleSubUV （粒子子 UV ）PixelDepth （像素深度）Power （求幂值）ReflectionVector （反射向量）

Material Expressions

Rotator （旋转器）ScalarParameter （标量参数）SceneDepth （场景深度）SceneTexture （场景贴图）ScreenPosition （屏幕位置）Sine （正弦）SquareRoot （开平方根）Subtract （减法）TextureCoordinate （贴图坐标 )

Material Expressions

TextureSample （贴图采样）TextureSampleParameter2D （贴图采样参数： 2D ）TextureSampleParameterCube （贴图采样参数：立方体） TextureSampleParameterMovie （贴图采样参数：影片）Time （计时）Transform （变换）

Material Expressions

VectorParameter （向量参数） VertexColor （顶点色）

Material Expressions

Issues about designing your own materials•Texture format: Targa （ .TGA ）。 It can accept other formats too.• Dimension of the texture: the power of 2. • Need not to be a square, e.g. 32, 1024, etc.• The number of pixels in width or height is not larger than 2048.• Make sure the resolution matches your need. For example, if you use a texture with resolution 2048x2048 but the players never have a chance to see it. Don’t do it.

Import textures1. Generic browser->File> Import 。2. Click OK3. A dialogue is shown to ask for more information

Package （包） : MyMaterials Group （組） : Textures If DeferCompression （不壓縮） is

checked, the package is not compressed before saving.

4. Save

A Walkthrough to build new materials

How to set a texture for TextureSample?

- Generic browser (Content Browser)->select a texture (highlight it)- Go back to Material Editor- Click the block of TextureSample

- at the line “Texture” (bottom of viewport)- Click “use the selected object in Content Browser”

Example

Example

• Try Pan• Try Rotation• Try Scaling• Try Relative

Alignment- Select the planes that you want to adjust, i.e. aligning all- Open Surface Properties -> Alignment->Planar

Hints

• After you select an object, press right mouse button.

• Additional actions will be shown for manipulating the object

• Select Geometry Mode (left hand side)• After you select a BSP, you can change the

texture coordinates by using widgets too.

BumpOffsetPurpose : Virtual Displacement MappingTo generate the illusion of height differences when normal map is used.Inputs : Height （高度值）和 UVs

Height: a scaling factor for heightHeightRatio （高度比） :pixel height / surface areaReferencePlane （参考平面）。 Determine how the displacement is computed, value in [0, 1]. Denote as h.

- If pixel height > h, move along the direction of camera- If pixel height <h, move in the negative direction of camera

BumpOffset

• Change “height value” from -1.0 to 2.0 and observe the effect

• Change ReferencePlane and observe the effect

Fresnel (value in [0,1])

Examples

• TexCoord• Panner• Rotator• OneMinus• Power• etc.

SpecularInstead of applying an intensity of specular uniformly over a surface, you can assign the intensity of specular to it based on a texture.

Exercises• Learn from UDK examples.

Exercises• Learn from UDK examples.

Summary

• Learn how to create materials.

• Material editing:http://www.youtube.com/watch?v=GP0jX5nUB50&feature=relatedhttp://www.youtube.com/watch?v=RIxQS66oIQE&feature=related