Experimental:Bloom TOP

Summary

The Bloom TOP creates a glow effect around bright parts of the image. It uses a combination of mipmaps of the image, where the first mipmap is the original image, the second mipmap is the image scaled down to half resolution, the third is quarter resolution and so on until the "top" mipmap is 1x1 pixel (the average of the whole image.)

It works by combining a range of mipmap levels (e.g., 2 to 7, or 3.4 to 9.5 -- fractional levels are supported) of the input image and and adding together a blurred image of each mipmap level.

The Bloom TOP runs in time roughly proportional to the number of mipmap levels that are sampled (determined by the Minimum and Maximum Bloom Size parameters discussed below).

bloomTOP_Class

Parameters - Bloom Page

Minimum Bloom Size minbloomsize - Determines the minimum mipmap level to start sampling from. It is [0, 1], so if the image has 10 mipmap levels and Minimum Bloom Size is set to .2, we will begin sampling from mipmap level 2. (The actual number of mipmap levels in the image is automatically determined by the image size.)

Maximum Bloom Size maxbloomsize - Determines the maximum mipmap level we sample from. It is [0, 1]. So if the image has 10 mipmap levels and Maximum Bloom Size is set to .8, we will sample mipmap levels up to level 8.

Ramp Alpha rampalpha - Applies a linear ramp to the range of sampled mipmap levels. It operates like the following graph, where x=0 represents the Minimum Bloom Size, and 1 the Maximum Bloom size: https://www.desmos.com/calculator/7cntitlit1 Thus it allows the user to weight higher or lower mipmap levels more or less. A value of .5 has no effect.

Bloom Intensity bloomintensity - Final multiplier of accumulated bloom value.

Original Image Mix originalmix - Multiplier for the original image value that is added in to the final output.

Brightness Bias brightnessbias - Amplifies the brightness of an incoming image according to a simple model, where any pixels above a threshold value ("Brightness Bias Knee") are subjected to a linear ramp from "Brightness Bias Level" to "Brightness Bias". This has the effect that bright areas of the image bloom more than they would otherwise, which is helpful if your image is not an HDR image. In the following graph, a is the knee, b is the level, and c is bias: https://www.desmos.com/calculator/8q0xdyttex

Brightness Bias Level brightnessbiaslevel - Level for brightness biasing below the threshold ("Knee")

Brightness Bias Knee brightnessbiasknee - Threshold above which the brightness of the image is amplified.

High Quality Bias highqualitybias - Brightness biasing can be "High Quality", meaning it is performed in a separate pass before the bloom is applied. If this pass is not performed, it works fine, but small bright blobs tend not to bloom very much. The separate pass adds a small amount of processing time, so it can be turned off if desired.

Normalize Bloom normalizebloom - When this is off, the shader simply adds all the smoothed mipmap level samples from Minimum to Maximum Bloom Size. So as you expand the range of mipmap levels, the bloom effect will brighten. This is because in adding more levels, you add more light, and thus the bloom overall gets brighter. You can remedy this manually if desired by lowering the Bloom Intensity. When Normalize Bloom is on, the accumulated bloom value is divided by the width of the interval over which is it accumulating bloom values, which has the effect that the overall bloom brightness is roughly constant when you change the min or max bloom size.

Parameters - Common Page

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

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.

Resolution Menu resmenu - A drop-down menu with some commonly used resolutions.

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.)

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

Aspect Menu armenu - A drop-down menu with some commonly used aspect ratios.

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

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.

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

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.

Operator Inputs

• Input 0: -

Info CHOP Channels

Extra Information for the can be accessed via an Info CHOP. Info Channels Common Page

Common Operator Info Channels

• total_cooks - Number of times the operator has cooked since the process started.

• cook_time - Duration of the last cook in milliseconds.

• cook_frame - Frame number when this operator was last cooked relative to the component timeline.

• cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.

• cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.

• cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.

• cooked_this_frame - 1 if operator was cooked this frame.

• warnings - Number of warnings in this operator if any.

• errors - Number of errors in this operator if any.

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