Experimental:TOP to CHOP

Summary

The TOP to CHOP converts pixels in a TOP image to CHOP channels. It generates one CHOP channel per scanline (row) in the image and per pixel color element (RGBA).

A single pixel, rows of pixels, columns of pixels or rectangular regions can be extracted from the image. It is therefore important to be aware of how many pixels your source image is composed of.

There is an optional input which supplies UV coordinates to sample the image. The input CHOP must contain 2 channels, for U and V. The first channel is always assumed to be U. The channels produced (red, green, blue and alpha) will be exactly as long as the input channel's length, with a value for each UV coordinate.

If you are grabbing pixels from a Depth TOP, you will only get a single channel (the depth). This will be placed in the R channel.

You can exclude pixels from being converted into CHOP samples using the Active Channel and/or Exclude NaNs parameters. For example, using the Active Channel parameter, pixels that have a zero value in the chosen channel are not copied over into the CHOP. This would, for example, exclude the invalid points in a Point File In TOP which have 0 in the Alpha channel when Active Channel is set to Alpha. When excluding pixels, the length of the CHOP (number of samples), will be set to the longest row of valid pixels. If this results in a channel with fewer valid samples than other channels, the Default Color parameter will be used to fill the remaining samples. If a scanline has zero valid pixels, than no CHOP channels will be created for that row.

The Output as Single Channel Set parameter can be used to merge each row of pixels into a single set of CHOP channels. With this option, the length of the CHOP is determined by the total number of valid pixels in the image.

toptoCHOP_Class

Parameters - Image Page

TOP top - Specify the TOP operator whose image will be sampled.

Download Type downloadtype - ⊞ - Gives the option for a delayed data download from the GPU, which is much faster and does not stall the render.

• Immediate (Slow) immediate -

• Next frame (Fast) nextframe -

Red r - Creates a CHOP channel per scanline with the prefix specified here, starting at 0. For example, the default is "r" in the Red field. If the specified TOP is a horizontal ramp that is 5 lines high, it creates five CHOP channels (r0 - r4) using the values of the red pixels in those scanlines.

Green g - Creates a CHOP channel per scanline with the prefix specified here, starting at 0. For example, the default is "r" in the Red field. If the specified TOP is a horizontal ramp that is 5 lines high, it creates five CHOP channels (r0 - r4) using the values of the red pixels in those scanlines.

Blue b - Creates a CHOP channel per scanline with the prefix specified here, starting at 0. For example, the default is "r" in the Red field. If the specified TOP is a horizontal ramp that is 5 lines high, it creates five CHOP channels (r0 - r4) using the values of the red pixels in those scanlines.

Alpha a - Creates a CHOP channel per scanline with the prefix specified here, starting at 0. For example, the default is "r" in the Red field. If the specified TOP is a horizontal ramp that is 5 lines high, it creates five CHOP channels (r0 - r4) using the values of the red pixels in those scanlines.

Output as Single Channel Set singleset - When turned on, channels will be combined so that there is one only one CHOP channel per color channel of the input image. By default, this parameter is off and there will be a separate set of CHOP channels for each row of the image. This parameter is only relevant when the Crop parameter is set to "Rows and Columns" or "Full Image" and multiple image rows are being converted. Rows are combined so that the bottom row of the cropped image comes first, followed by the second row, the third row, and so forth.

Exclude NaNs excludenans - Pixels that include a Not-A-Number (NaN) value in any of their channels will be skipped and not converted into CHOP samples. This can be useful for images created by the Point File In TOP where pixels that do not represent valid points are assigned a NaN value.

Active Channel activechannel - ⊞ - Selects a channel of the input image to use as a mask so that pixels that are set to zero in that channel are skipped and not converted into CHOP samples. This can work with the Active channel settings in the Point File In TOP or Ouster TOP to exclude pixels that have invalid point data. It is equivalent to the Active instance parameter in the Geometry COMP that ignores instances where the Active value is zero.

• None none - The active channel is not used, and all pixels (except those affected by the Exclude NaN parameter) are converted into CHOP samples.

• Red red - Only pixels with a non-zero value in the red channel will be converted to CHOP samples.

• Green green - Only pixels with a non-zero value in the green channel will be converted to CHOP samples.

• Blue blue - Only pixels with a non-zero value in the blue channel will be converted to CHOP samples.

• Alpha alpha - Only pixels with a non-zero value in the alpha channel will be converted to CHOP samples.

RGBA Units rgbaunit - ⊞ - Scales the output to lie in the range 0-1, 0-255 or 0-65535.

• 0 to 1 u1 -

• 0 to 255 u256 -

• 0 to 65535 u65536 -

Parameters - Crop Page

Crop crop - ⊞ - Specifies what to extract from the image.

• Pixel (U,V) pixel -

• Row (U) row -

• Column (V) col -

• Rows and Columns block -

• Full Image full -

UV Units uvunits - ⊞ - Specifies the units for the following 4 parameters. The parameters can use the local variables $NR and $NC for the number of rows and columns.

• 0 to 1 norm -

• Pixels pixel -

U Start ustart - Starting point for sampling in U. Values outside the range of the image are determined by the image's extend conditions, in the extend page.

U End uend - Ending point for sampling in U.

V Start vstart - Starting point for sampling in V.

V End vend - Ending point for sampling in V.

Interpolate interp - ⊞ - Determines the interpolation method when UV sampling with an input CHOP.

• Nearest Sample nearest -

• Linear linear -

Parameters - Extend Page

Image Left imageleft - ⊞ - The image extend conditions when sampling the image with U less than 0.

• Hold hold -

• Cycle cycle -

• Mirror mirror -

• Default Color default -

Image Right imageright - ⊞ - The image extend conditions for U greater than 1.

• Hold hold -

• Cycle cycle -

• Mirror mirror -

• Default Color default -

Image Bottom imagebottom - ⊞ - The image extend conditions for V less than 0.

• Hold hold -

• Cycle cycle -

• Mirror mirror -

• Default Color default -

Image Top imagetop - ⊞ - The image extend conditions for V greater than 1.

The extend conditions are:

• Hold hold - Use the first or last pixel value.

• Cycle cycle - Loop back to the other side of the image.

• Mirror mirror - Zig-zag back into the image.

• Default Color default - Use a default color specified below.

Default Color defcolor - ⊞ - The color to use when outside the bounds of the image, and the Default Color extend condition is set.

• Red defcolorr -

• Green defcolorg -

• Blue defcolorb -

• Alpha defcolora -

Parameters - Channel Page

Start start - The start position of the channel, expressed in units set by the units menu to the right (samples, frames or seconds). The channel length is determined by the number of pixels in each scanline that is converted into a channel.

Start Unit startunit - Select the units to use for this parameter, Samples, Frames, or Seconds.

Sample Rate rate - The sample rate of the channels, in samples per second.

Extend Left left - ⊞ - The left extend conditions (before/after range).

• Hold hold - Hold the current value of the channel.

• Slope slope - Continue the slope before the start of the channel.

• Cycle cycle - Cycle the channel repeatedly.

• Mirror mirror - Cycle the channel repeatedly, mirroring every other cycle.

• Default Value default - Use the constant value specified in the Default Value parameter

Extend Right right - ⊞ - The right extend conditions (before/after range).

• Hold hold - Hold the current value of the channel.

• Slope slope - Continue the slope after the end of the channel.

• Cycle cycle - Cycle the channel repeatedly.

• Mirror mirror - Cycle the channel repeatedly, mirroring every other cycle.

• Default Value default - Use the constant value specified in the Default Value parameter

Default Value defval - The value used for the Default Value extend condition.

Parameters - Common Page

Time Slice timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.

Scope scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.

Sample Rate Match srselect - ⊞ - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.

• Resample At First Input's Rate first - Use rate of first input to resample others.

• Resample At Maximum Rate max - Resample to the highest sample rate.

• Resample At Minimum Rate min - Resample to the lowest sample rate.

• Error If Rates Differ err - Doesn't accept conflicting sample rates.

Export Method exportmethod - ⊞ - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.

• DAT Table by Index datindex - Uses the docked DAT table and references the channel via the index of the channel in the CHOP.

• DAT Table by Name datname - Uses the docked DAT table and references the channel via the name of the channel in the CHOP.

• Channel Name is Path:Parameter autoname - The channel is the full destination of where to export to, such has geo1/transform1:tx.

Export Root autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.

Export Table exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).

Operator Inputs

• Input 0 -