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# Vertex Lighting

Lights a mesh based on light reaching each polygon vertex.

## When Vertex Lighting occurs in Unreal

- on meshes
- not on BSP (uses lightmaps)
- Originally built into rendering software
- Built into 3D graphics cards for speed

## How it works

Each polygon has a minimum of 3 vertices. If light is cast towards the polygon, each vertex will usually receieve a differing light level. Vertex lighting blends the light level on the surface of the polygon based on the vertex light levels.

Because of this blend, neighboring polygons will also appear smooth, resulting in a smooth mesh surface even if the mesh geometry is coarse. However, a coarse polygon will still be detected by seeing its edges and comes with its own set of problems.

Can mesh light smoothing be toggled?

Foxpaw: In UT there is an actor setting bCurvyMesh which I believe does this. In UT2003 I believe you can do it using materials, but I can't say that with certainty.

### Stretched light or shadow

- Since light based on polys
  - avoid long stretched polys
  - Use even spaced polys for maximum light and shadow clarity

[show image]

### low polygon

- [show light] in center fade to black on edges
- [show light] on one edge fade to black

### No shadow

- onto BSP lightmap world
- onto other meshes

## Solutions

### Smooth shading

- prevents shade 'stepping'

### Mesh detail

- Tesselation increases polygon count
- Increased polygons = increased lighting detail

### Weld vertices

Dont place static mesh on top or near others

- Make one mesh by welding vertices
- SHadows calcualted across entire mesh

## If its still to bright or dark

You can always toggle a few parameters in the mesh's display properties:

- bStaticTrue → false
  - alters lighting on badly lit meshes
  - explain what it does
  - can look funny
  - [show image]
- Displayglow
  - 1.0 is maximum
- Ambientglow
  - changes overall lighting
- enable bUnlit
  - Full bright mesh reveals texture only
  - uses no lighting
- toggle bShadowcast
  - mesh doesnt block light

### Projectors (UT2003 and later)

- If mesh is not bright but surrounding area is
- example: light area around a lamp mesh
- if BSP world is correctly lit
  - - project light onto mesh only

## Related Topics

- Hourences' tute: http://planetunreal.com/phalanx/tut%27s/tutorial_vertex.htm
- General lighting

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