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Texture Mapping from Watt, Ch. 8 Jonathan Han Topics Discussed Texture Map to Models Bump Maps, Light Maps Environment (Reflection) Mapping 3D Textures Interactive Texture Mapping What is Mapping? Assigning colors to the pixels on a 3D model to simulate. . . Color Specular ‘color’

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Texture Mapping from Watt, Ch. 8

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Presentation Transcript
topics discussed
Topics Discussed
  • Texture Map to Models
  • Bump Maps, Light Maps
  • Environment (Reflection) Mapping
  • 3D Textures
  • Interactive Texture Mapping
what is mapping
What is Mapping?

Assigning colors to the

pixels on a 3D model to

simulate. . .

  • Color
  • Specular ‘color’
  • Surface perturbation
  • Transparency
2d texture maps to polygon mesh objects
2D Texture Maps to Polygon Mesh Objects
  • Association of 2 coordinate systems between the mesh and the map
  • Inverse Mapping vs. Forward Mapping
  • Bilinear Interpolation
  • Problem is parametrization of object surface
mapping by intermediate surface
Mapping by Intermediate Surface
  • Map -> (S map) Simple 3D shape -> (O map) Projection onto complex mesh
  • Plane, cylinder, cube, spheres all possible intermediate shapes
bi cubic parametric patch
Bi-Cubic Parametric Patch
  • If an object is already a quadric or a cubic, then the surface possess a coordinate system that covers every point already.
  • Simply multiply u and v by the resolution in pixels to obtain location on texture map
parametric patch cont d
Parametric Patch (cont’d)
  • Divide mesh up to individual parametric surfaces, and place the texture over each
parametric patch cont d11
Parametric Patch (cont’d)
  • Assign (u, v) coordinates to points on mesh surface, and interpolate between these points
  • Technique to create pseudo-realistic 3D objects when viewed in constricted directions
bump mapping
Bump mapping
  • Simulation for surface perturbation without adding polygons to the mesh
  • The lighting changes per-pixel to achieve said simulation
what is a bump map
What is a Bump Map?
  • Array of values that represent object’s height variation on small scale
  • Combined with surface normal to evaluate lighting equation
light maps
Light Maps
  • Like Bump Maps, Light Maps store information on a surface that’s not just color
  • Simulate localized lighting
  • Same map applied to multiple mesh to create the same lighting pattern
light maps example
Light Maps Example

No light maps

With light maps

environmental mapping
Environmental Mapping
  • To substitute expensive ray-tracing for modelling shiny objects, 2D environment map are textured onto the object.
creating an environmental map
Creating an Environmental Map
  • Sphere map:
  • Render scene from opposite angle of output camera, and apply as texture map
  • Problem: Inaccurate when the object is round
creating an environmental map19
Creating an Environmental Map
  • Ball Map:
  • Create a mirrored sphere and place at approximate location of object – render the sphere.
  • Problem: Non-uniform sampling at non-original viewpoint
creating an environmental map20
Creating an Environmental Map
  • Cube Map:
  • Place a camera at location of object and remove object – take snapshots at 6 directions.
extended environmental mapping
Extended Environmental Mapping
  • Surface Properties:
  • 2 maps – diffuse and specular, combined like in Phong shading
  • Diffuse: Indexed by surface normal
  • Specular: Indexed by reflected view vector
3 d texture domains
3-D Texture Domains
  • Instead of a 2D texture pattern, why not make the texture 3D?
  • Circumvent problems in texture compression and texture continuity
  • Problem: Only have texture that are defined in 3D
easy example
Easy Example
  • If Z-axis integer is even, make it red. If not, make it white.
easy example no 2
Easy Example No. 2
  • Sine and ramp functions
3d noise
3D Noise
  • Used to distort existing texture to form irregular and interesting patterns
perlin s noise lattice
Perlin’s Noise Lattice
  • The Perlin’s Method of Noise Generation:
  • Lattice of points (i,j,k), where i, j, and k are integers – each assigned a random number. Values between i, j, and k linearly (or otherwise) interpolated
adjusting noise
Adjusting Noise
  • Instead of noise(x,y,z), we can use noise(f*x,f*y,f*z) * a to fine-tune result
  • f – frequency
  • a - amplitude
creating recognizable textures
Creating Recognizable Textures
  • Turbulate stripes to emulate marble texture
  • (marble(x) = marble_colour (sin(x + turbulence(x))
3d textures for animation
3D Textures for Animation
  • Emulate flame by adding time dimension to 3D Texture Map
  • Successive “slices” of noise rendered for flickering flame
interactive texturing
Interactive Texturing
  • Assist artists in creating helpful textures
  • Applet
  • Applet
interactivity in texturing symmetrical models
Interactivity in Texturing Symmetrical Models
  • Model placed in bounding box
  • Artist paints profile texture as 2D image
  • Image plane-textured onto the model
  • Artist adjusts image and re-render for results
painting textures
“Painting” Textures
  • Artist “paints” textures onto models directly
  • Imbues shading, glossiness, as well as pattern to model spontaneously as artist selects it
implementing texture paint
Implementing Texture “Paint”
  • Auxiliary frame buffer – item buffer – created
  • Screen cursor’s location on model gives pointer to position on object surface
  • Requires parametrized surface – divide object’s surface into numerous micropolygons
  • Additional possibilities for “clever” ways around expensive modelling?
  • Applications for 3D textures and noise? In combination with environmental mapping? In combination with light maps and bump maps?