BBLM (File Format)

The BBLM (Binary BLooM) filetype controls blur, bloom and color filtering of the final image output.

File Description

The result of the threshold operation

The result of the first blur

The result of the second blur

The final image output after applying bloom

The game handles bloom by going through a number of stages whereby each stage alters either the original image (the output without posteffect) or the result of a previous stage in its own way. The four main stages are threshold, blur, bloom and tinting. Each stage and its own steps are described below.

Threshold

The threshold stage is the first one to be executed by the game. It works with a grayscale and the fully colored version.of the original image. It performs a thresholding action by subtracting the product of the threshold intensity and the threshold color from the grayscale image. This means that it is also possible to filter out specific color channels, although Mario Kart Wii itself only uses grayscale colors as threshold. The exact purpose of the threshold intensity is unclear, since the BBLM file already gives full control over the threshold color. The resulting image - a darkened version of the grayscale input - is then multiplied with the colored input to create a darkened color image.

Blur

BBLM supports up to two distinct blurs, with the second one supporting 4 stages. The BBLM format, however, only supports 2 stages in the second blur and any attempt to add more stages will cause defects. Mario Kart Wii applies blur by translating the input image in a circle around its original location. The first stage in both blurs divides this circle in 8 steps, the second stage uses 16 steps. All steps are added together into one final result, with the blur color intensity (values 0.0 to 1.0) determining how much the final image is darkened and the blur strength determining what radius is used for the circle. Note that an intensity of 1 will make the final result too bright, since the blur operation adds 8 variants of the same image together. The second blur takes the result of the first blur as input and is then repeated with its own output.

Bloom

The bloom stage contains two substages: the first substage combines the result of the two blur operations (A), and the second stage applies a threshold of 50% (so 127 is subtracted from each color channel) to the original image and makes the result four times brighter (B). The final result is calculated using the following formula: (1-B) * A. So the brightest parts of the original image darken the blur, which makes blur only cover the darker parts of the original image.

Tint

Tint is a fairly simple stage. Once the final result is generated, tint adds a color filter over it, which works just like a vertex color. The most noticable usage of this tint effect is the cave in Mushroom Gorge, which is given a green ambience by this stage.

File Format

Offset	Type	Description
0x00	String	File magic. Always PBLM in ASCII.
0x04	UInt32	File size. Always 0xA4 in MKW.
0x08	UInt8	Version. Always 01 in MKW.
0x0C	UInt32	Unknown. Always 00 00 00 00.
0x10	Float	Threshold intensity
0x14	Byte[4]	Threshold color
0x18	Byte[4]	Tint color
0x1C	Short	Bitfield
0x20	Float	First blur strength
0x24	Float	First blur color intensity
0x28	Uint32[6]	Unknown. Always 00 00 00 00.
0x40	Float	Second blur stage 1 strength
0x44	Float	Second blur stage 1 color intensity
0x48	Uint32[6]	Unknown. Always 00 00 00 00.
0x60	Float	Second blur stage 2 strength. Unused, since the value from stage 1 is used instead.
0x64	Float	Second blur stage 2 color intensity
0x68	Uint32[6]	Unknown. Always 00 00 00 00.
0x80	Uint8	Determines how the generated output image (source) is blended with the original image (destination). Source and destination are always added together. Value Output 0 No modifications. 1 The source is multiplied with its complement (inverted color), thus discarding the brightest color channels. 2 The tint alpha determines the transparency of the source. 3 Same as 2, but the destination is multiplied with the inverted alpha, creating a weighted average. 4 The source is multiplied with itself, emphasising the brighter colors.
0x81	Uint8	Number of blur stages in the second blur.
0x9c	Float[2]	Bloom color intensity per stage

Tools

The following tools can handle BBLM files:

• Post-Effect Editor, by Wexos