# Experimental:Limit TOP

## Summary

The Limit TOP can limit the pixel values of the input image to fall between a minimum and maximum value, and can quantize the pixels by value or position.

Limiting a channel causes all of its values to lie within the given range. Several different methods are available to determine what happens to values outside of the Minimum/Maximum range.

Quantizing pixel values will snap each channel to the closest allowable value (the "quantized values"). Quantizing methods are: Floor, Ceiling, and Round.

Quantizing pixel positions will cause all pixels within the quantization step to take the same value. This is equivalent to lowering the image resolution and then scaling the image back to its original size with no filtering applied.

## Parameters - Limit Page

Minimum Function minop - - The wrapping method used when applying limits to the pixel values in the image.

• Off off - No limits are applied to the pixel values.
• Clamp clamp - Pixel values are constrained to the ranged defined by the Minimum and Maximum parameters. Values outside of the range are replaced with the Minimum or Maximum value.
• Loop loop - Values outside of the Minimum/Maximum range continue at the other end of the interval e.g. as values go above the Maximum they loop back and start again at the Minimum value.
• Zig Zag zigzag - When values go beyond the Minimum or Maximum values they mirror back towards the other end of the range e.g. when a value goes above the maximum it flips and starts going back to the minimum.

Maximum Function maxop - - The wrapping method used when applying limits to the pixel values in the image.

• Off off - No limits are applied to the pixel values.
• Clamp clamp - Pixel values are constrained to the ranged defined by the Minimum and Maximum parameters. Values outside of the range are replaced with the Minimum or Maximum value.
• Loop loop - Values outside of the Minimum/Maximum range continue at the other end of the interval e.g. as values go above the Maximum they loop back and start again at the Minimum value.
• Zig Zag zigzag - When values go beyond the Minimum or Maximum values they mirror back towards the other end of the range e.g. when a value goes above the maximum it flips and starts going back to the minimum.

Minimum Value min - The minimum value that any of the channels in the output image can have.

Maximum Value max - The maximum value that any of the channels in the output image can have.

Positive Only positive - Apply an absolute value function after all other limits and quantizations are calculated e.g. all negatives are made positive.

Normalize norm - Normalize values in the output image so that they are all scaled and shifted to fall between the Normalized Minimum and Maximum (0 to 1 by default). This operation requires multiple internal render passes and is slightly slower than other limit operations. Normalization is done after all other limits and quantizations are applied.

Normalize Minimum normmin - The minimum value for pixels after normalization.

Normalize Maximum normmax - The maximum value for pixels after normalization.

## Parameters - Quantize Page

Quantize Value quantvalue - - The function used to quantize the pixel values in the output image.

• Off off - Pixel values are not quantized.
• Ceiling ceiling - Pixel values are rounded up to the nearest quantization step.
• Floor floor - Pixel values are rounded down to the nearest quantization step.
• Round round - Pixel values are rounded to the nearest quantization step.

Value Step vstep - The quantization step size for pixel values.

Value Offset voffset - An offset for the quantization step so that it doesn't have to lie on zero.

Quantize Position quantpos - - The function used for spacial quantization e.g. quantizing the UV coordinates so that pixel values are merged into larger blocks.

• Off off - Position (spacial) quantization is not used.
• Ceiling ceiling - Pixels are rounded up to the nearest spacial quantization step (towards the top-right).
• Floor floor - Pixels are rounded down to the nearest spacial quantization step (towards the bottom-left).
• Round round - Pixels are rounded towards the nearest quantization step.

Position Step posstep - The size of the spacial quantization step in UV space (0-1)

Position Offset posoffset - An offset applied to the spacial quantization so that the steps do not have to start at 0,0 (measured in 0-1 UV space).

## Parameters - Common Page

Output Resolution outputresolution - - quickly change the resolution of the TOP's data.

• Use Input useinput - Uses the input's resolution.
• Eighth eighth - Multiply the input's resolution by that amount.
• Quarter quarter - Multiply the input's resolution by that amount.
• Half half - Multiply the input's resolution by that amount.
• 2X 2x - Multiply the input's resolution by that amount.
• 4X 4x - Multiply the input's resolution by that amount.
• 8X 8x - Multiply the input's resolution by that amount.
• Fit Resolution fit - Multiply the input's resolution by that amount.
• Limit Resolution limit - Multiply the input's resolution by that amount.
• Custom Resolution custom - Enables the Resolution parameter below, giving direct control over width and height.

Resolution resolution - - Enabled only when the Resolution parameter is set to Custom Resolution. Some Generators like Constant and Ramp do not use inputs and only use this field to determine their size. The drop down menu on the right provides some commonly used resolutions.

• W resolutionw -
• H resolutionh -

Use Global Res Multiplier resmult - Uses the Global Resolution Multiplier found in Edit>Preferences>TOPs. This multiplies all the TOPs resolutions by the set amount. This is handy when working on computers with different hardware specifications. If a project is designed on a desktop workstation with lots of graphics memory, a user on a laptop with only 64MB VRAM can set the Global Resolution Multiplier to a value of half or quarter so it runs at an acceptable speed. By checking this checkbox on, this TOP is affected by the global multiplier.

Output Aspect outputaspect - - Sets the image aspect ratio allowing any textures to be viewed in any size. Watch for unexpected results when compositing TOPs with different aspect ratios. (You can define images with non-square pixels using xres, yres, aspectx, aspecty where xres/yres != aspectx/aspecty.)

• Use Input useinput - Uses the input's aspect ratio.
• Resolution resolution - Uses the aspect of the image's defined resolution (ie 512x256 would be 2:1), whereby each pixel is square.
• Custom Aspect custom - Lets you explicitly define a custom aspect ratio in the Aspect parameter below.

Aspect aspect - - Use when Output Aspect parameter is set to Custom Aspect.

• Aspect1 aspect1 -
• Aspect2 aspect2 -

Input Smoothness inputfiltertype - - This controls pixel filtering on the input image of the TOP.

• Nearest Pixel nearest - Uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
• Interpolate Pixels linear - Uses linear filtering between pixels. This is how you get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
• Mipmap Pixels mipmap - Uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail.

Fill Viewer fillmode - - Determine how the TOP image is displayed in the viewer. NOTE:To get an understanding of how TOPs work with images, you will want to set this to Native Resolution as you lay down TOPs when starting out. This will let you see what is actually happening without any automatic viewer resizing.

• Use Input useinput - Uses the same Fill Viewer settings as it's input.
• Fill fill - Stretches the image to fit the edges of the viewer.
• Fit Horizontal width - Stretches image to fit viewer horizontally.
• Fit Vertical height - Stretches image to fit viewer vertically.
• Fit Best best - Stretches or squashes image so no part of image is cropped.
• Fit Outside outside - Stretches or squashes image so image fills viewer while constraining it's proportions. This often leads to part of image getting cropped by viewer.
• Native Resolution nativeres - Displays the native resolution of the image in the viewer.

Viewer Smoothness filtertype - - This controls pixel filtering in the viewers.

• Nearest Pixel nearest - Uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
• Interpolate Pixels linear - Uses linear filtering between pixels. Use this to get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
• Mipmap Pixels mipmap - Uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail.

Passes npasses - Duplicates the operation of the TOP the specified number of times. Making this larger than 1 is essentially the same as taking the output from each pass, and passing it into the first input of the node and repeating the process. Other inputs and parameters remain the same for each pass.

Channel Mask chanmask - Allows you to choose which channels (R, G, B, or A) the TOP will operate on. All channels are selected by default.

Pixel Format format - - Format used to store data for each channel in the image (ie. R, G, B, and A). Refer to Pixel Formats for more information.

• Use Input useinput - Uses the input's pixel format.
• 8-bit fixed (RGBA) rgba8fixed - Uses 8-bit integer values for each channel.
• sRGB 8-bit fixed (RGBA) srgba8fixed - Uses 8-bit integer values for each channel and stores color in sRGB colorspace.
• 16-bit float (RGBA) rgba16float - Uses 16-bits per color channel, 64-bits per pixel.
• 32-bit float (RGBA) rgba32float - Uses 32-bits per color channel, 128-bits per pixels.
• 10-bit RGB, 2-bit Alpha, fixed (RGBA) rgb10a2fixed - Uses 10-bits per color channel and 2-bits for alpha, 32-bits total per pixel.
• 16-bit fixed (RGBA) rgba16fixed - Uses 16-bits per color channel, 64-bits total per pixel.
• 11-bit float (RGB), Positive Values Only rgba11float - A RGB floating point format that has 11 bits for the Red and Green channels, and 10-bits for the Blue Channel, 32-bits total per pixel (therefore the same memory usage as 8-bit RGBA). The Alpha channel in this format will always be 1. Values can go above one, but can't be negative. ie. the range is [0, infinite).
• 16-bit float (RGB) rgb16float -
• 32-bit float (RGB) rgb32float -
• 8-bit fixed (Mono) mono8fixed - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 8-bits per pixel.
• 16-bit fixed (Mono) mono16fixed - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
• 16-bit float (Mono) mono16float - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
• 32-bit float (Mono) mono32float - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 32-bits per pixel.
• 8-bit fixed (RG) rg8fixed - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 8-bits per channel, 16-bits total per pixel.
• 16-bit fixed (RG) rg16fixed - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 16-bits per channel, 32-bits total per pixel.
• 16-bit float (RG) rg16float - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 16-bits per channel, 32-bits total per pixel.
• 32-bit float (RG) rg32float - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 32-bits per channel, 64-bits total per pixel.
• 8-bit fixed (A) a8fixed - An Alpha only format that has 8-bits per channel, 8-bits per pixel.
• 16-bit fixed (A) a16fixed - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
• 16-bit float (A) a16float - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
• 32-bit float (A) a32float - An Alpha only format that has 32-bits per channel, 32-bits per pixel.
• 8-bit fixed (Mono+Alpha) monoalpha8fixed - A 2 channel format, one value for RGB and one value for Alpha. 8-bits per channel, 16-bits per pixel.
• 16-bit fixed (Mono+Alpha) monoalpha16fixed - A 2 channel format, one value for RGB and one value for Alpha. 16-bits per channel, 32-bits per pixel.
• 16-bit float (Mono+Alpha) monoalpha16float - A 2 channel format, one value for RGB and one value for Alpha. 16-bits per channel, 32-bits per pixel.
• 32-bit float (Mono+Alpha) monoalpha32float - A 2 channel format, one value for RGB and one value for Alpha. 32-bits per channel, 64-bits per pixel.

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An Operator Family that creates, composites and modifies images, and reads/writes images and movies to/from files and the network. TOPs run on the graphics card's GPU.

The width and height of an image in pixels. Most TOPs, like the Movie File In TOP can set the image resolution. See Aspect Ratio for the width/height ratio of an image, taking into account non-square pixels.

The viewer of a node can be (1) the interior of a node (the Node Viewer), (2) a floating window (RMB->View... on node), or (3) a Pane that graphically shows the results of an operator.

A CHOP outputs one or more channels, where a channel is simply a sequence of numbers, representing motion, audio, etc. Channels are passed between CHOPs in TouchDesigner networks. See also Export.