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80 lines
3.0 KiB
Markdown
80 lines
3.0 KiB
Markdown
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# B3D Reader & Writer
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## `b3d.read(file)`
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Reads from `file`, which is expected to provide `file:read(nbytes)`. `file` is not closed.
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Returns a B3D model object.
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## `:write(file)`
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Writes the B3D model object `self` to `file`.
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`file` must provide `file:write(bytestr)`. It should be in binary mode.
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It is not closed after writing.
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## `:write_string()`
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Writes the B3D model object to a bytestring, which is returned.
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## `:to_gltf()`
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Returns a glTF JSON representation of `self` in Lua table format.
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## `:write_gltf(file)`
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Convenience function to write the glTF representation to `file` using modlib's `json` writer.
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`file` must provide `file:write(str)`. It is not closed afterwards.
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## Examples
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### Converting B3D to glTF
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This example loops over all files in `dir_path`, converting them to glTFs which are stored in `out_dir_path`.
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```lua
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local modpath = minetest.get_modpath(minetest.get_current_modname())
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local dir_path = modpath .. "/b3d"
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local out_dir_path = modpath .. "/gltf"
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for _, filename in ipairs(minetest.get_dir_list(dir_path, false --[[only files]])) do
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-- First read the B3D
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local in_file = assert(io.open(dir_path .. "/" .. filename, "rb"))
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local model = assert(b3d.read(in_file))
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in_file:close()
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-- Then write the glTF
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local out_file = io.open(out_dir_path .. "/" .. filename .. ".gltf", "wb")
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model:write_gltf(out_file)
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out_file:close()
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end
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```
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### [Round-trip (minifying B3Ds)](https://github.com/appgurueu/modlib_test/blob/f11c8e580e90454bc1adaa11a58e0c0217217d90/b3d.lua)
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This example from [`modlib_test`](https://github.com/appgurueu/modlib_test) reads, writes, and then reads again,
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in order to verify that no data is lost through writing.
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Simply re-writing a model using modlib's B3D writer often reduces model sizes,
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since for example modlib does not write `0` weights for bones.
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Keep in mind to use the `rb` and `wb` modes for I/O operations
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to force Windows systems to not perform a line feed normalization.
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### [Extracting triangle sets](https://github.com/appgurueu/ghosts/blob/42a9eb9ee81fc6760a0278d23e4c47bc68bb4919/init.lua#L41-L79)
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The [Ghosts](https://github.com/appgurueu/ghosts/) mod extracts triangle sets using the B3D module
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to then approximate the player shape using particles picked from these triangles.
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### [Animating the player](https://github.com/appgurueu/character_anim/blob/c48b282c0b42b32294ec2fddc03aa93141cbd894/init.lua#L213)
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[`character_anim`](https://github.com/appgurueu/character_anim/) uses the B3D module to determine the bone overrides required
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for animating the player entirely Lua-side using bone overrides.
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### [Generating a Go board](https://github.com/appgurueu/go/blob/997ce85260d232a05dd668c32c6854bf34e3d5be/build/generate_models.lua)
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This example from the [Go](https://github.com/appgurueu/go) mod generates a Go board
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where for each spot on the board there are two pieces (black and white),
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both of which can be moved out of the board using a bone.
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It demonstrates how to use the writer (and how the table structure roughly looks like).
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