copyright 2015 - curt hill meshes a little more to know
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Copyright © 2015 - Curt Hill
Meshes
A Little More to Know
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
Collision Mesh
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
Select a Material
Copyright © 2015 - Curt Hill
Right Click
Copyright © 2015 - Curt Hill
Material Editor
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
The Graph
Copyright © 2015 - Curt Hill
The Channels
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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
Copyright © 2015 - Curt Hill
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