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Obj2Fce with fcecodec

This tutorial describes how to prepare OBJ/MTL files for the Obj2Fce converter scripts. This tutorial covers FCE3, FCE4, and FCE4M.

The latest version of this tutorial can be found here.
The following files can be found in /scripts

bfut_Fce2Obj.py
bfut_Obj2Fce3 (material to triagflag).py
bfut_Obj2Fce3 (material to triagflag, material to texpage).py
bfut_Obj2Fce4 (material to triagflag).py
bfut_Obj2Fce4 (material to triagflag, material to texpage).py
bfut_Obj2Fce4M (material to triagflag).py
bfut_Obj2Fce4M (material to triagflag, material to texpage).py
bfut_Obj2Fce3 (do not center parts, material to triagflag).py
bfut_Obj2Fce3 (do not center parts, material to triagflag, material to texpage).py
bfut_Obj2Fce4 (do not center parts, material to triagflag).py
bfut_Obj2Fce4 (do not center parts, material to triagflag, material to texpage).py
bfut_Obj2Fce4M (do not center parts, material to triagflag).py
bfut_Obj2Fce4M (do not center parts, material to triagflag, material to texpage).py

How to use

Run one of the script versions in a terminal

python <bfut_Obj2Fce*.py> /path/to/model.obj

Prerequisites

Install fcecodec from https://github.com/bfut/fcecodec
Install numpy from https://numpy.org/install
Install tinyobjloader from https://github.com/tinyobjloader/tinyobjloader/tree/master/python

Introduction

Create an OBJ example that showcases some of the herein discussed concepts, with

python bfut_Fce2Obj.py /path/to/model.fce

FCE4 and FCE4M are very similar to each other. Certain differences are discussed in this tutorial at this time.

fcecodec functions allow changing most FCE properties.

Part name vs. part order

<partname>

In FCE4 and FCE4M, only the part name defines a part's role (e.g., :HB is FCE4 high body).

In FCE3, only the part order defines a part's role and its name can be arbitrary (e.g., part index 0 is FCE3 high body).
The optional hidden lights part in FCE always has part index 12.

For complete part name and part order listings, see /src/fcelib/fcelib_fcetypes.h

Damage model (FCE4, FCE4M)

<partname>
DAMAGE_<partname>

Example: Once :HB high body is finished, create a copy named DAMAGE_:HB.
In this new part, only change vertice positions or vertice normals.

For a list of parts that use damage models in-game, see /src/fcelib/fcelib_fcetypes.h

Part center

<partname>
POSITION_<partname>

A custom part center is highly desirable for driver animation (:OD, :PHdriver), where the part center should be in the middle of the steering wheel. Also useful for :OS spoiler animation.

To define a custom part center, create a helper part POSITION_<partname>. The helper part's centroid will be used as center in <partname>.

As default if no helper part is found, for each part its centroid will be used as part center. Default behavior is highly desirable for the following: wheels, front brakes, driver head.

The do not center parts scripts will leave the coordinate origin as center for all parts (not recommended for FCE3, FCE4M).

Vertice animation flag (FCE4, FCE4M)

<partname>
ANIMATED_##_<partname>

(FCE4) :OD
(FCE4M) :PHdriver

For driver animation, vertices are either movable or immovable. To set movable verts, they have to be enclosed within at least one cuboid helper part ANIMATED_##_<partname>, where # is a digit 0-9. See screenshot below.

Helper part names must not be duplicated, hence the digits.

Default behavior if no helper part is found: all vertices for this part are movable.

Vertice animation flags do not seem to have any visible effect on any of the other animated parts (wheels, front brakes, driver head, movable spoiler, and everything dash.fce).

vert animation flag

Dummies (Light / FX objects)

DUMMY_##_<dummyname>

To create dummy <dummyname>, create a helper part called DUMMY_##_<dummyname>, where # is a digit 0-9. The part centroid will be the dummy position. Only the part name and its centroid are significant.

Helper part names must not be duplicated, hence the digits. <Dummynames> can be duplicated at will.

For dummynames and their effects, see /src/fcelib/fcelib_fcetypes.h

Triangle flags

Triangle flags can be assigned with the material to triagflag scripts.

In FCE, each triangle has a triangle flag, which is a positive integer value. Triangle flags values and their effects are identical across FCE3, and FCE4, in sofar they are implemented in-game. It is generally possible to set any integer value, even if it has no effect in-game.

The Obj2Fce converter scripts set triangle flags from tags in material names.

The order of the tags is not significant. A material name can include additional elements that are not tags.

Triangle flag Tag Hex value fce version
default _FDEF_ 0x000 all
matte (no reflection) _FMAT_ 0x001 all
high chrome _FHIC_ 0x002 all
no cull _FNOC_ 0x004 all
semi-transparent _FSET_ 0x008 all
? (unknown 1) _FUN1_ 0x010 ?
all windows _FALW_ 0x020 FCE4/FCE4M
front window _FFRW_ 0x040 FCE4/FCE4M
left window _FLEW_ 0x080 FCE4/FCE4M
back window _FBAW_ 0x100 FCE4/FCE4M
right window _FRIW_ 0x200 FCE4/FCE4M
broken window _FBRW_ 0x400 FCE4/FCE4M
? (unknown 2) _FUN2_ 0x800 ?

Example: A non-broken window on the left side in FCE4 may have triangle flag 0x0AE. This can be set by assigning the triangle to a material name that includes _FHIC_FNOC_FSET_FALW_FLEW_ (i.e., high chrome, no cull, semi-transparent, all windows, left window).

This paragraph can be skipped: With the Obj2Fce scripts, it is also possible to use the raw hex value as material name, i.e., 0x0AE. However, the advantage of using triangle flag tags is, that they can be combined with a texture page tag, see next section below. Also, it avoids constantly dealing with mathematics. Briefly, on the meaning behind the final hex value. 0x0AE is equal to 0x002 + 0x004 + 0x008 + 0x020 + 0x080 (use a calculator). The visible in-game effect is the same when an integer that is greater or equal than 0x1000 is added. For example, 0x0AE + 0xB3000 is equal to 0xB30AE, which again ticks the high chrome, no cull, semi-transparent, all windows, left window triangle flags. Hex value 0xB3000 should have the same visible in-game effect as 0x000.

(FCE4M) The above values are identical. Additionally, FCE4M introduced damage textures that are assigned using triangle flags, using new values combined with using multiple texture pages. The specifics are out of the scope of this tutorial at this time.

For more details, see /src/fcelib/fcelib_fcetypes.h

Texture page (FCE3/FCE4 officer models, FCE4 pursuit road objects, FCE4M damage textures)

Texture pages can be assigned with the material to texpage scripts.

Similarly to triangle flags, in FCE, each triangle is assigned a texture page, which is a positive integer value. The Obj2Fce converter scripts look for and use the first tag in a material name that fits the below scheme.

A texture page tag and triangle flag tags can both be present in a material name. A material name can include additional elements that are not tags.

For officer models and pursuit road objects, the NumArts value must equal the greatest used texture page minus 1. In all other cases, NumArts = 1.

Texture pages are not relevant for, car.fce (FCE3, FCE4) and dash.fce (FCE4, FCE4M).

Texture page Tag Hex value
0 (no tag) 0x000
1 _T1_ 0x001
2 _T2_ 0x002
<i> _T<i>_ hex(<i>)

Example: For texture page 0, no tag is needed. For texture page 4, add tag _T4_ to the material name.

Information

Obj2Fce License: zlib License
Fce2Obj License: zlib License
fcecodec License: GNU General Public License v3.0+
Website: https://github.com/bfut/fcecodec