modlib/b3d.lua

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local metatable = {__index = getfenv(1)}
--! experimental
--+ Reads a single BB3D chunk from a stream
--+ Doing `assert(stream:read(1) == nil)` afterwards is recommended
--+ See `b3d_specification.txt` as well as https://github.com/blitz-research/blitz3d/blob/master/blitz3d/loader_b3d.cpp
--> B3D model
function read(stream)
local left = 8
local function byte()
left = left - 1
return assert(stream:read(1):byte())
end
local function int()
local value = byte() + byte() * 0x100 + byte() * 0x10000 + byte() * 0x1000000
if value >= 2^31 then
return value - 2^32
end
return value
end
local function id()
return int() + 1
end
local function optional_id()
local id = int()
if id == -1 then
return
end
return id + 1
end
local function string()
local rope = {}
while true do
left = left - 1
local char = assert(stream:read(1))
if char == "\0" then
return table.concat(rope)
end
table.insert(rope, char)
end
end
local function float()
-- TODO properly truncate to single floating point
local byte_4, byte_3, byte_2, byte_1 = byte(), byte(), byte(), byte()
local sign = 1
if byte_1 >= 0x80 then
sign = -1
byte_1 = byte_1 - 0x80
end
local exponent = byte_1 * 2
if byte_2 >= 0x80 then
byte_2 = byte_2 - 0x80
exponent = exponent + 1
end
local mantissa = ((((byte_4 / 0x100) + byte_3) / 0x100) + byte_2) / 0x80
if exponent == 0xFF then
if mantissa == 0 then
return sign * math.huge
end
-- TODO differentiate quiet and signalling NaN as well as positive and negative
return 0/0
end
if exponent == 0 then
-- subnormal value
return sign * 2^-126 * mantissa
end
return sign * 2 ^ (exponent - 127) * (1 + mantissa)
end
local function float_array(length)
local list = {}
for index = 1, length do
list[index] = float()
end
return list
end
local function color()
return {
r = float(),
g = float(),
b = float(),
a = float()
}
end
local function vector3()
return float_array(3)
end
local function quaternion()
return {[4] = float(), [1] = float(), [2] = float(), [3] = float()}
end
local function content()
assert(left >= 0, stream:seek())
return left ~= 0
end
local chunk
local chunks = {
TEXS = function()
local textures = {}
while content() do
table.insert(textures, {
file = string(),
flags = int(),
blend = int(),
pos = float_array(2),
scale = float_array(2),
rotation = float()
})
end
return textures
end,
BRUS = function()
local brushes = {}
brushes.n_texs = int()
assert(brushes.n_texs <= 8)
while content() do
local brush = {
name = string(),
color = color(),
shininess = float(),
blend = float(),
fx = float(),
texture_id = {}
}
for index = 1, brushes.n_texs do
brush.texture_id[index] = optional_id()
end
table.insert(brushes, brush)
end
return brushes
end,
VRTS = function()
local vertices = {
flags = int(),
tex_coord_sets = int(),
tex_coord_set_size = int()
}
assert(vertices.tex_coord_sets <= 8 and vertices.tex_coord_set_size <= 4)
local has_normal = (vertices.flags % 2 == 1) or nil
local has_color = (math.floor(vertices.flags / 2) % 2 == 1) or nil
while content() do
local vertex = {
pos = vector3(),
normal = has_normal and vector3(),
color = has_color and color(),
tex_coords = {}
}
for tex_coord_set = 1, vertices.tex_coord_sets do
local tex_coords = {}
for tex_coord = 1, vertices.tex_coord_set_size do
tex_coords[tex_coord] = float()
end
vertex.tex_coords[tex_coord_set] = tex_coords
end
table.insert(vertices, vertex)
end
return vertices
end,
TRIS = function()
local tris = {
brush_id = id(),
vertex_ids = {}
}
while content() do
table.insert(tris.vertex_ids, {id(), id(), id()})
end
return tris
end,
MESH = function()
local mesh = {
brush_id = optional_id(),
vertices = chunk{VRTS = true}
}
mesh.triangle_sets = {}
repeat
local tris = chunk{TRIS = true}
table.insert(mesh.triangle_sets, tris)
until not content()
return mesh
end,
BONE = function()
local bone = {}
while content() do
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local vertex_id = id()
assert(not bone[vertex_id], "duplicate vertex weight")
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local weight = float()
if weight > 0 then
-- Many exporters include unneeded zero weights
bone[vertex_id] = weight
end
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end
return bone
end,
KEYS = function()
local flags = int()
local _flags = flags % 8
local rotation, scale, position
if _flags >= 4 then
rotation = true
_flags = _flags - 4
end
if _flags >= 2 then
scale = true
_flags = _flags - 2
end
position = _flags >= 1
local bone = {
flags = flags
}
while content() do
table.insert(bone, {
frame = int(),
position = position and vector3() or nil,
scale = scale and vector3() or nil,
rotation = rotation and quaternion() or nil
})
end
-- Ensure frames are sorted ascending
table.sort(bone, function(a, b) return a.frame < b.frame end)
return bone
end,
ANIM = function()
return {
-- flags are unused
flags = int(),
frames = int(),
fps = float()
}
end,
NODE = function()
local node = {
name = string(),
position = vector3(),
scale = vector3(),
keys = {},
rotation = quaternion(),
children = {}
}
local node_type
-- See https://github.com/blitz-research/blitz3d/blob/master/blitz3d/loader_b3d.cpp#L263
-- Order is not validated; double occurences of mutually exclusive node def are
while content() do
local elem, type = chunk()
if type == "MESH" then
assert(not node_type)
node_type = "mesh"
node.mesh = elem
elseif type == "BONE" then
assert(not node_type)
node_type = "bone"
node.bone = elem
elseif type == "KEYS" then
assert((node.keys[#node.keys] or {}).frame ~= (elem[1] or {}).frame, "duplicate frame")
modlib.table.append(node.keys, elem)
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elseif type == "NODE" then
table.insert(node.children, elem)
elseif type == "ANIM" then
node.animation = elem
else
assert(not node_type)
node_type = "pivot"
end
end
-- TODO somehow merge keys
return node
end,
BB3D = function()
local version = int()
local self = {
version = {
major = math.floor(version / 100),
minor = version % 100,
raw = version
},
textures = {},
brushes = {}
}
assert(self.version.major <= 2, "unsupported version: " .. self.version.major)
while content() do
local field, type = chunk{TEXS = true, BRUS = true, NODE = true}
if type == "TEXS" then
modlib.table.append(self.textures, field)
elseif type == "BRUS" then
modlib.table.append(self.brushes, field)
else
self.node = field
end
end
return self
end
}
local function chunk_header()
left = left - 4
return stream:read(4), int()
end
function chunk(possible_chunks)
local type, new_left = chunk_header()
local parent_left
left, parent_left = new_left, left
if possible_chunks and not possible_chunks[type] then
error("expected one of " .. table.concat(modlib.table.keys(possible_chunks), ", ") .. ", found " .. type)
end
local res = assert(chunks[type])()
assert(left == 0)
left = parent_left - new_left
return res, type
end
local self = chunk{BB3D = true}
return setmetatable(self, metatable)
end
-- TODO function write(self, stream)
local binary_search_frame = modlib.table.binary_search_comparator(function(a, b)
return modlib.table.default_comparator(a, b.frame)
end)
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--> [bonename] = { position = vector, rotation = quaternion, scale = vector }
function get_animated_bone_properties(self, keyframe, interpolate)
local function get_frame_values(keys)
local values = keys[keyframe]
if values and values.frame == keyframe then
return {
position = values.position,
rotation = values.rotation,
scale = values.scale
}
end
local index = binary_search_frame(keys, keyframe)
if index > 0 then
return keys[index]
end
index = -index
assert(index > 1 and index <= #keys)
local a, b = keys[index - 1], keys[index]
if not interpolate then
return a
end
local ratio = (keyframe - a.frame) / (b.frame - a.frame)
return {
position = (a.position and b.position and modlib.vector.interpolate(a.position, b.position, ratio)) or a.position or b.position,
rotation = (a.rotation and b.rotation and modlib.quaternion.interpolate(a.rotation, b.rotation, ratio)) or a.rotation or b.rotation,
scale = (a.scale and b.scale and modlib.vector.interpolate(a.scale, b.scale, ratio)) or a.scale or b.scale,
}
end
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local bone_properties = {}
local function get_props(node)
local properties = {}
if node.keys and next(node.keys) ~= nil then
properties = modlib.table.add_all(properties, get_frame_values(node.keys))
end
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for _, property in pairs{"position", "rotation", "scale"} do
properties[property] = properties[property] or modlib.table.copy(node[property])
end
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if node.bone then
assert(not bone_properties[node.name])
bone_properties[node.name] = properties
end
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for _, child in pairs(node.children or {}) do
get_props(child)
end
end
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get_props(self.node)
return bone_properties
end