RingFilt

A state machine based filtering program that fits a surface to the one-ring or two-ring of triangles around each point and filters away points & triangles according to the specified filter.

Note: The Ring filtering state machine always assumes that we need at least the 2-ring for filtering. Which implies we need a 3-ring before we can safely delete any vertices. This has the side effect of reordering vertices and triangles on output to satisfy this 2-ring property. For instance, You may notice re-ordered meshes drawing all interior vertices first and then vertices on the border later.

Note: All Filters have been modified to support LOW / HIGH thresholding, if those flags are specified (-zsplit and -zsub).

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Filter Flags

Types of supported filters

-fnon

Run DO NOTHING filter

• Pass thru filter, does no filtering, except for re-order side-effect mentioned above

-f1r

Run Simple Average Height Filter on 1-Ring of each vertex

• Computes best fit z-value as average of neighbors in 1-ring

-f2r

Run Simple Average Height Filter on 2-Ring of each vertex

• Computes best fit z-value as average of neighbors in both 1-ring and 2-ring

-fl1r

Run Plane Fitting (Linear Least Squares) Filter on 1-ring of each vertex

• Computes best fit plane to data points in 1-ring
• Needs at least 3 data points to compute best fit plane
• Reverts to -f1r filter if there are not enough data points
• best-fit z-value as computed from planar equation for current x,y
• z = Ax + By + C

-fq2r

Run Quadratic Surface Fitting (Linear Least Squares) filter on 2-ring of each vertex

• Computes best fit quadratic surface thru data points in 1-ring and 2-ring
• Needs at least 6 data points to compute best fit surface
• Reverts to -fl1r filter if there are not enough data points
• best-fit z-value as computed from quadratic equation for current x,y
• z = Ax^2 + By^2 + Cxy + Dx + Ey + F

-flhi1r

Run LOW / HIGH isolated filter on 1-ring filter of each vertex

• If point is LOW and all neighbors in 1-ring are HIGH, mark as filtered
• If point is HIGH and all neighbors in 1-ring are LOW, mark as filtered
• In both cases, best fit z-value is computed as simple average of neighbors z-values
• Need to specify valid -zsplit and -zsub flags to make this filter do any useful work

-flhi2r

Run LOW / HIGH isolated filter on 2-ring filter of each vertex

• If point is LOW and all neighbors in 1-ring and 2-ring are HIGH, mark as filtered
• If point is HIGH and all neighbors in 1-ring and 2-ring are LOW, mark as filtered
• In both cases, best fit z-value is computed as simple average of neighbors z-values
• Need to specify valid -zsplit and -zsub flags to make this filter do any useful work

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Filter Modifier Flags

Modifiers to supported filters

-fpmin

Run Local Minima Filter variation (works with -f1r, -f2r, -fl1r, -fq2r flags)

• If z-value is below best-fit z-value, it gets filtered

-fpmax

Run Local Maxima Filter varation (works with -f1r, -f2r, -fl1r, -fq2r flags)

• if z-value is above best-fit z-value, it gets filtered

-fpvar

Run Variance Filter varation default (works with -f1r, -f2r, -fl1r, -fq2r flags)

• if variance of best-fit z-value is outside the variance range [minSigma, maxSigma] it gets filtered

-sigmin {floatVal} 

Min Variance Value for variance filters, (variances smaller than this get filtered away) defaults to 0.0 if not specified.

-sigmax {floatVal} 

Max Variance Value for variance filters, (variances larger than this get filtered away) defaults to 3.0 if not specified.

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Disposal Policy Flags

Controls what to do with a vertex if it is marked as filtered

-replace

Replace any filtered vertices with the computed best-fit z-value

-delete

Delete filtered vertices (also deletes all incident triangles on deleted vertex)

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Low / High Thresholding

-zsplit {floatVal} 

threshold value,

• if (zVal <= threhold) then the current vertex belongs to the LOW group
• otherwise it belongs to HIGH group

-zsub {floatVal} 

Value to subtract from high group before filtering operations

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Input / Output Files

Note: Both of these flags need to be specified for this app to work properly.

-i {filename}

Input file to read and filter

-o {filename}

Output file to write out

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Input File Formats

Note: Unlike other tools, at least one of these must be specified for this app to work properly.

-isma

Use Streaming Mesh ASCII

-ismb

Use Streaming Mesh Binary

-ismc

Use Streaming Mesh Compressed

-ismd

Use Streaming Mesh Compressed (???)

-iply

Use Stanford's PLY format

-ijrs

Use Jonathon's Shewchuk's .ele and .node format

-ioff

Use OFF file format

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Output File Formats

Note: Unlike other tools, at least one of these must be specified for this app to work properly.

Streaming Point Formats

-ospa

Use Streaming POINT ASCII

• All triangle commands are suppressed when writing to this format
• You get a point cloud, which needs to be spatially finalized (via spfinalize)

-ospb

Use Streaming POINT Binary

• All triangle commands are suppressed when writing to this format
• You get a point cloud, which needs to be spatially finalized (via spfinalize)

Streaming Mesh Formats

-osma

Use Streaming Mesh ASCII

-osmb

Use Streaming Mesh Binary

-osmc

Use Streaming Mesh Compressed

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Miscellaneous Flags

-compact

Turn on compaction (i.e. prereadaspre wrapper)

-vcompact

Turn on compaction (i.e. prereadaspre wrapper)

-bbox

Compute Min/Max Bounding Box

-b

Bit Rate for Compressed formats on output

-bits {intVal} 

Bit Rate for Compressed formats on output

-delay_read {intVal}

Number of triangles to buffer on reading

-dry

??? (Write Flag)

-utf

Use Triangle Finalize (

• Eliminates stand-a-lone finalize commands on output to ASCII output file formats (IE .sma).

-h

Help, Show example usage for "RingFilt"

-- ChristianStith - 17 Jun 2008

• Shawndb_Progress_Ring_filter.ppt: slides of early usage of Ring filter

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