BGLPBD (File Format)

BGLPBD files (Binary Graphics Light Probe Bake Data) are AAMP files used in Mario Kart 8 and Mario Kart 8 Deluxe. They contain cached light probes used to render global illumination in tracks. In Mario Kart 8 they are found within each track's folder with the name course.bglpbd. In Mario Kart 8 Deluxe, they're compressed using Yaz0 into SZS files, named course_bglpbd.szs.

File Format

The file format is no different from other AAMP files.

Structure

BGLPBD files found in Mario Kart 8 and Mario Kart 8 Deluxe consist of a root AABB voxel-based grid that can be subdivided in more sub-grids. These files make use of spherical harmonics in order to render global illumination on drivers, vehicles, items and some course objects

Root structure

Parameter name	Description
root_grid	Contains information about the root AABB grid.
param_obj	Version, number of grids and global lighting parameters.

root_grid

Parameter name	Type	Description
aabb_min_pos	Vector3f	Minimum point of the root AABB grid.
aabb_max_pos	Vector3f	Maximum point of the root AABB grid.
voxel_step_pos	Vector3f	Voxel subdivision size. The grid is divided in n voxels of this size.

param_obj

Parameter name	Type	Description
version	UInt32	BGLPBD version. Always 1.
dir_light_indirect	Float	Direct light indirect effect scale.
point_light_indirect	Float	Point light indirect effect scale.
spot_light_indirect	Float	Spot light indirect effect scale.
emission_scale	Float	Emission effect scale.
used_box_num	UInt32	Number of used sub-grids.

Sub-grid

Each AABB sub-grid (named b_ followed by its index number) consists of a buffer of light probes per voxel. It contains its own structure and parameters.

Sub-grid structure

Parameter name	Description
param_obj	Grid index and type.
grid	Contains information about the AABB voxel sub-grid.
sh_index_buffer	Buffer of indices used to determine which light probes are used in each voxel.
sh_data_buffer	Buffer of light probe spherical harmonic values stored as single-precision floats.

param_obj

Parameter name	Type	Description
index	UInt32	Index of this sub-grid.
type	UInt32	Grid type. Always 0.

grid

Parameter name	Type	Description
aabb_min_pos	Vector3f	Minimum point of this AABB grid.
aabb_max_pos	Vector3f	Maximum point of this AABB grid.
voxel_step_pos	Vector3f	Voxel subdivision size. The grid is divided in n voxels of this size.

sh_index_buffer

Parameter name	Type	Description
type	UInt32	Buffer type. Always 1 (index buffer).
used_index_num	UInt32	Number of used indices. This number determines how many of the voxels' indices can be used for light calculations.
max_index_num	UInt32	Number of total indices (n).
index_buffer	UInt32[n]	Buffer of light probe indices. This buffer contains 8 integers per voxel (presumably one per vertex). They are assigned to the float arrays from the light probe data buffer.

sh_data_buffer

Parameter name	Type	Description
type	UInt32	Buffer type. Always 0 (data buffer).
max_sh_data_num	UInt32	Number of total light probes (n).
used_data_num	UInt32	Number of used light probes.
per_probe_float_num	UInt32	Number of spherical harmonic values per probe. Always 27.
data_buffer	Float[n]	Buffer of light probe spherical harmonics. This buffer consists of 27 floats (3 for each of its 9 coefficients per spherical harmonic) per light probe.

Tools

The following tools can handle BGLPBD files:

• (none)