Normal Mapping

Transcript

1. From texture mapping to parallax mapping — Normal Mapping Bruce Tsai
2. Texture Mapping • Add surface texture to 3D model 2
3. 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 3
4. Lighting Phong Reflection Model 4
5. Dot3 Lighting • Per-pixel lighting • Dot = Nx * Lx 
 + Ny * Ly 
 + Nz * Lz 5
6. Bump Mapping • Want more details on object surface • NOT want to increase polygons
7. 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 7
8. Height Map Black and white grayscale image 8
9. Normal Map • Contain modified normal of surface directly • Lead more predictable results • (R, G, B) -> (X, Y, Z) 9
10. Normal Map 10
11. 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 11
12. Tangent space normal map Object space normal map
13. 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 13
14. 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 14
15. What is a Normal Map?
16. 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