Texture Synthesis on Surfaces - PowerPoint PPT Presentation

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Texture Synthesis on Surfaces

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Texture Synthesis on Surfaces Paper by Greg Turk Presentation by Jon Super – PowerPoint PPT presentation

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Title: Texture Synthesis on Surfaces


1
Texture Synthesis on Surfaces
  • Paper by Greg Turk
  • Presentation by Jon Super

2
Texture Synthesis on Surfaces

3
Goals of texture placement
  • Take a 2D texture and wrap it onto a surface
  • Avoid noticeable seams between patches
  • Minimize stretching and distortion
  • Produce a natural-looking result

4
The next best thing
  • Lapped Textures Praun et al. SIGGRAPH00
  • Uses many overlapped texture patches
  • Aligns patches with underlying vector field
  • Generally minimizes distortion

5
The next best thing
  • Lapped textures shortcomings
  • Low-frequency components
  • Boundary mismatch
  • Direction field singularities

6
Texture synthesis to the rescue!
7
Process
  • Create a mesh hierarchy over the model
  • Set up a vector field over the mesh
  • Calculate sweep distance for each vertex
  • Assign colors based on neighbors

8
Process
  • Create a mesh hierarchy over the model
  • Set up a vector field over the mesh
  • Calculate sweep distance for each vertex
  • Assign colors based on neighbors

9
Mesh Hierarchy
  • Equivalent of a Gaussian pyramid to a surface
  • Multiple layers of different resolutions
  • Each layer has 4 times the number of vertices of
    the layer above it
  • Each layer contains every vertex of the layer
    above it

10
Point placement
  • n points randomly placed on the surface
  • Repulsion between the points spaces them evenly
  • These points are now fixed in place, representing
    level m of an m-level mesh
  • Repeated for each layer, adding 3 times more
    points each time (3n, 12n, etc)

11
Connectivity
  • Connectivity between vertices of each layer
  • Delaunay triangulation applied
  • Mesh is connected in a web of triangles

12
Mesh hierarchy operations
  • Interpolation
  • Low-pass filtering
  • Downsampling
  • Upsampling

13
Process
  • Create a mesh hierarchy over the model
  • Set up a vector field over the mesh
  • Calculate sweep distance for each vertex
  • Assign colors based on neighbors

14
Vector field
  • Provides order to the placement of the texture on
    the model
  • Each mesh vertex is given a vector
  • User initiates the process by defining a few key
    vectors (12)

15
Vector field creation
  • All vertices not user-defined set to 0
  • User-defined vectors are downsampled to the
    coarsest mesh
  • Low-pass filtering to fill out top mesh
  • Upsample for each layer to fill to bottom

16
Process
  • Create a mesh hierarchy over the model
  • Set up a vector field over the mesh
  • Calculate sweep distance for each vertex
  • Assign colors based on neighbors

17
Surface sweeping
  • Uses the directional flow of the vector field to
    assign ordering to the vertices
  • Ordering will allow a sort of raster scan over
    the 3D model
  • The color in the image
  • cycles as the sweep
  • distance increases

18
Sweep distance calculation
  • Select an anchor point to base the distance
  • Each vertex takes the value that is the weighted
    sum of what its neighbors think
  • Distance along the flow direction added to the
    neighbors sweep distance
  • Sweep distances will propagate out from the
    anchor until every vertex has one

19
Process
  • Create a mesh hierarchy over the model
  • Set up a vector field over the mesh
  • Calculate sweep distance for each vertex
  • Assign colors based on neighbors

20
Pixel Neighborhoods
  • Similar technique to 2D texture synthesis
  • Examine nearby colors and look for a similar
    pattern in the texture image
  • Different kinds of pixel neighborhoods

21
Mesh coordinate space
  • Pixel neighborhoods dont translate directly to
    the unorganized vertices in a mesh
  • Vertex vector is down
  • Rotate 90 degrees CCW for right

22
Multi-level synthesis
  • Start at top, work down
  • Initialize the vertices of mesh layer k with
    color values from Gaussian pyramid layer k
  • Make a pass with the half square
  • Top layer should have a crude representation of
    the texture

23
Multi-level synthesis
  • Extrapolate and refine each lower level
  • Extrapolate initializes the colors using a large
    full square neighborhood of the level above
  • Refine improves on that by combining a large full
    square on the current level with a small full
    square on the level above

24
Algorithm
25
Results
26
Results
27
Results
28
Results
29
Results
30
Results
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