# Blur TOP

## Summary

The Blur TOP blurs the image with various kernel filters and radii. It can do multi-pass blurs and can do horizontal-only or vertical-only blurs.

Use Pre-shrink when the blurs are high and you want to optimize performance.

Tip: Filter Size is expressed in pixels. If you want resolution-independent blurs, use an expression like `me.par.resolutionw/100` in the Filter Size parameter, which gives a 1% image blur.

## Parameters - Blur Page

Method `/method` - Determines how the blur is applied.

• Horizontal and Vertical - Blur is applied in both x (horizontal) and y (vertical).
• Horizontal - Blur is applied in x direction only.
• Vertical - Blur is applied in y direction only.

Type `/type` - Determines the mathematical function used to create the blur.

• Catmull-Rom - A spline approximation to a Gaussian kernel. Gives sharper textures and more accurate edges.
• Gaussian - A normal distribution where pixels at the center have more effect on the resulting pixel. Gaussian lacks sharpness but handles ringing and aliasing well.
• Box - Each pixel within the box is weighted evenly. Inexpensive and gives a "boxy" look.
• Barlette - A triangle filter. The weight of each pixel is a linear function of its distance from the center.
• Sinc - A sharpening filter. Some pixels contribute a negative weight to the result, artifacts may occur in the form of "ringing". Keeps small details and edges better than Gaussian.
• Hanning - A cosine approximation to a Gaussian kernel.
• Blackman - A higher order cosine approximation to a Gaussian kernel.

Wrap Mode `/wrapmode` - Sets the extend conditions to determine what happens to the blur at the edge of the image.

• Clamp to Edge - The blur is clamped at the edges.
• Repeat - The blur is calculated as if the image was repeating (tiled - blurring at the bottom of image that would fall outside the image edges will appear at top of image).
• Mirror and Repeat - The blur is calulated as if the image was mirrored and repeating.

Pre-Shrink `/preshrink` - Reduces the image's resolution before applying the blur.

Filter Size `/size` - The amount of blur in pixels.

Sample Step `/offset` - When sampling the image, this determines the distance from each pixel to the sample pixel. When units are set to pixels, it is the number of pixels away from the current pixel which is sampled to blur the image. A Sample Step of 3 would sample pixels 3 pixels away.

Rotate Kernel `/rotate` - Rotates the blur filter. More noticeable when Method is set to Horizontal.

Dither `/dither` - Enabling makes 8-bit blurs look smoother. This can help if the blur operation introduces banding or other unexpected artifacts.

## Parameters - Common Page

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

• Use Input - uses the input's resolution.
• Eighth, Quarter, Half, 2X, 4X, 8X - multiply the input's resolution by that amount.
• Fit Resolution - Resizes the input to the size specified in Resolution using the best possible match that does not crop any of the input. It will resize the image to be larger than the input resolution if a larger resolution is specified. It's a "fit inside", Aspect Ratio is maintained.
• Limit Resolution - Limits the input to the size specified in Resolution using the best possible match that does not crop any of the input. It will NOT resize the image to be larger than the input resolution if a larger resolution is specified. It's a "fit inside", Aspect Ratio is maintained.
• Custom Resolution - enables the Resolution parameter below, giving direct control over width and height.

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.

Use Global Res Multiplier - 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 - 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.)

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

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

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

• Nearest Pixel - uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
• Interpolate Pixels - 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 - 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 - determine how the TOP image is displayed in the viewer.

• Input - uses the same Fill Viewer settings as it's input.
• Fill - stretches the image to fit the edges of the viewer.
• Fit Horizontal - stretches image to fit viewer horizontally.
• Fit Vertical - stretches image to fit viewer vertically.
• Fit Best - stretches or squashes image so no part of image is cropped.
• Fit 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 - displays the native resolution of the image in the viewer.

NOTE: To get an understanding of how TOPs works 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.

Viewer Smoothness - This controls pixel filtering in the viewers.

• Nearest Pixel - uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
• Interpolate Pixels - 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 - uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail. When the input is 32-bit float format, only nearest filtering will be used (regardless of what is selected).

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

• Input - uses the input's pixel format.
• 8-bit fixed (RGBA) - uses 8-bit integer values for each channel.
• sRGB 8-bit fixed (RGBA) - uses 8-bit integer values for each channel and stores color in sRGB colorspace.
• 16-bit float (RGBA) - uses 16-bits per color channel, 64-bits per pixel.
• 32-bit float (RGBA) - uses 32-bits per color channel, 128-bits per pixels.

• 10-bit RGB, 2-bit Alpha, fixed (RGBA) - uses 10-bits per color channel and 2-bits for alpha, 32-bits total per pixel.
• 16-bit fixed (RGBA) - uses 16-bits per color channel, 64-bits total per pixel.
• 11-bit float (RGB), Positive Values Only - 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).
• 8-bit fixed (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 8-bits per pixel.
• 16-bit fixed (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
• 16-bit float (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
• 32-bit float (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 32-bits per pixel.
• 8-bit fixed (RG) - 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) - 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) - 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) - 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) - An Alpha only format that has 8-bits per channel, 8-bits per pixel.
• 16-bit fixed (A) - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
• 16-bit float (A) - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
• 32-bit float (A) - An Alpha only format that has 32-bits per channel, 32-bits per pixel.
• 8-bit fixed (Mono+Alpha) - 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) - 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) - 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) - A 2 channel format, one value for RGB and one value for Alpha. 32-bits per channel, 64-bits per pixel.