normal mapping

From texture mapping to parallax mapping — Normal Mapping

Bruce Tsai

Texture Mapping• Add surface texture to 3D model

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Normal Mapping

• Dot3 bump mapping

• Technique used for faking lighting of bumps and dents

• Only affect shading rather than surface

• An implementation of bump mapping

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LightingPhong Reflection Model

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Dot3 Lighting

• Per-pixel lighting

• Dot = Nx * Lx + Ny * Ly + Nz * Lz

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Bump Mapping• Want more details on

object surface

• NOT want to increase polygons

Bump Map (Height Map)• Invented by Blinn

• Simulate surface displacement yielding modified normal

1. Look up height in height map

2. Calculate surface normal (finite difference)

3. Combine calculated surface normal with geometric surface normal

4. Calculate interaction of new “bumpy” surface with lights in the scene

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Height MapBlack and white grayscale image

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Normal Map• Contain modified normal of surface directly

• Lead more predictable results

• (R, G, B) -> (X, Y, Z)

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Normal Map

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Two Type Normal Maps• Tangent space

• Store normals relative to surface

• Use on models to be deformed

- Animated character

• Object space

• Store all normals on a unit sphere

• Use on model to be rotated without deformed

- Weapons, vehicle, building

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Tangent space normal map

Object space normal map

Tangent Space• Pros

• Reuse map

• Tile or mirror map

• Overlay painted details

• Use image compression

• Cons

• Smoothing problems from low-poly vertex normals

• Slower performance

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Object Space• Pros

• Generate high-quality curvature

• Slightly better performance

• Cons

• Cannot easily reuse map

• Difficult to tile or mirror

• Harder to overlay painted details

• Cannot be compressed well

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What is a Normal Map?

Reference• www.cs.brandeis.edu/~cs155/Lecture_17.pdf

• http://graphics.cs.williams.edu/papers/SteepParallaxI3D05/

• http://en.wikipedia.org/wiki/Normal_mapping

• http://en.wikipedia.org/wiki/Bump_mapping

• http://www.3dkingdoms.com/tutorial.htm

• http://docs.cryengine.com/display/SDKDOC4/Tangent+Space+Normal+Mapping

• http://gamedevelopment.tutsplus.com/articles/gamedev-glossary-what-is-a-normal-map--gamedev-3893

• http://youtu.be/yHzIx41eiD4

• https://en.wikipedia.org/wiki/Heightmap

• www.falloutsoftware.com/tutorials/gl/normal-map.html

• www.bencloward.com/tutorials_normal_maps1.shtml

• http.developer.nvidia.com/CgTutorial/cg_tutorial_chapter05.html

• https://en.wikipedia.org/wiki/Phong_reflection_model