Copyright © Curt Hill Meshes A Little More to Know

Copyright © 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 © 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 detail Copyright © Curt Hill

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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 polygons Copyright © 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 © 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 © Curt Hill

Collision Mesh Copyright © 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 © 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 © 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 © 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 © 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 © 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 © Curt Hill

Select a Material Copyright © Curt Hill

Right Click Copyright © Curt Hill

Material Editor Copyright © 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 © Curt Hill

The Graph Copyright © Curt Hill

The Channels Copyright © 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 © 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 © 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 © 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 © 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 © Curt Hill