Copyright 2015 - Curt Hill Meshes A Little More to Know

Copyright © 2015 - Curt Hill

Meshes

A Little More to Know


Introduction • Here we find out what a static

mesh actor really is• We will also get a brief introduction

to the Material Editor

What is a mesh?• A group of polygons with edges in common that compose a three dimensional shape– The polygons contain vertices and

edges– A polygon also has a face

• The mesh may enclose a three dimensional irregular solid or just be a shell

• The more polygons– The finer the detail– The more work to render


Polygon Count• AKA Polycount• Games typically use a much smaller

polycount than movies– Games need to be rendered in real-time

while a movie does not need this speed• Modern GPUs know about these

polygons– The number they can process is one of

the ways to rate them• In a game, we must balance speed

with detailCopyright © 2015 - Curt Hill


Pictures

UDK and Meshes• UDK does not create meshes• They function as a template

– Many copies may be placed in a level– These come from a 3D modeling

program• In the editor they may be moved,

scaled and covered with material • A static mesh is composed of more

than just polygonsCopyright © 2015 - Curt Hill

Static Mesh Pieces• The first component is a polygonal

mesh• What is not obvious is that there

are other things• The collision mesh• Material

– Either the default or a proper covering• UV Sets

– However materials need to be explained as well


Collision Mesh• A simplified containing mesh

– Simplified to make computations easier• Will detect a collision when in real life

the items would be close but not collide

• A simple cube mesh is not substantially different than its collision mesh

• The more complicated the mesh the more the collision mesh is simplified


Collision Mesh


Materials• We are only interested in a polygon if

we can see it– What we see is the polygon face

• A polygon may express the physical detail of a mesh but it is boring

• Thus we map a material onto the mesh– You have seen the default material

• When we do each face has an image superimposed on it– This tends to obscure the edges


What is a material?• Strictly speaking it is an algorithm• A material may contain one or

more textures– A texture is just an image

• A material also defines how light reflects off of the face– How the material interacts with the

light– Glossy or matte are two examples


Channels• The material algorithm uses as its

input a set of channels• Each channel defines a certain

quality that is visually apparent• These channels operate on the

pixels• Since pixels are just integers,

representing RGB and Alpha, they may modified with simple mathematical operations


Channel Types• Diffuse – Original image or texture

• Specular– Reflectivity or shininess - depends on the

light and relative position• Normal

– Used to create surface effects such bumpiness

• Emissive– How much light does this produce

• Opacity – determines transparency• Others as well


UV Mapping• The texture that is part of the

material is a 2D plane which has to be applied to 3D surface

• This is known as a mapping• The two axes of the planar image

are the U (horizontal) and V (vertical)– Hence UV Mapping


Material Editor• Since we are creating a new

algorithm from pieces it can get rather complicated

• Uses the same sort of graph approach as Kismet


Select a Material


Right Click


Material Editor


Working Areas• Material Editor has several main

working areas• Menu – top • Preview pane – left • Property pane – bottom• Graph pane – middle• There are others not shown

– Source code


The Graph


The Channels


Finally on Materials• You thought that the material

covering was simple!• We will come back to the material

editor when we look at a simple application– Materialing speedtree vegetation


Static Mesh• Finally we know what a static mesh

is• It is:

– an invisible polygon mesh – Wrapped in a visible UV map– Contained within an invisible collision

mesh• Some of these may be absent

– You have seen: no collision model– You have also seen the default material


How is this different than CSG?

• CSG is typically simple shapes– Planes, cones spheres– These cannot be moved or destroyed

• Static meshes are usually much more complicated – They are made outside of UDK– They may become part of a static

mesh actor


Static Mesh Actor• Usually a prop in the world

– Cannot be damaged– Does not move much, although can

be animated with Kismet/Matinee• We may also derive a new Actor

object and it refers to this static mesh– Then we may animate with

UnrealScript


Conclusion• Although we have been using

static meshes from the first creation of a level we did not know much about them– Now we know slightly more


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Copyright 2015 - Curt Hill Meshes A Little More to Know