F3DEX3/docs/Documentation/Porting your Romhack.md

@page porting Porting Your Romhack Codebase to F3DEX3

Porting Your Romhack Codebase to F3DEX3

For an OoT codebase, only a few minor changes are required to use F3DEX3. However, more changes are recommended to increase performance and enable new features.

How to modify the microcode in your HackerOoT based romhack (note that this is already done in HackerOoT, so this is provided as a guide for other games):

• Replace include/ultra64/gbi.h in your romhack with gbi.h from this repo.
• Make the "Required Changes" listed below.
• Build this repo: install the latest version of armips, then make F3DEX3_BrZ or make F3DEX3_BrW.
• Copy the microcode binaries (build/F3DEX3_X/F3DEX3_X.code and build/F3DEX3_X/F3DEX3_X.data) to data in your romhack repo.
• In data/rsp.rodata.s, change the line between fifoTextStart and fifoTextEnd to .incbin "data/F3DEX3_X.code" (or wherever you put the binary), and similarly change the line between fifoDataStart and fifoDataEnd to .incbin "data/F3DEX3_X.data". After both the fifoTextEnd and fifoDataEnd labels, add a line .balign 16.
• If you are planning to ever update the microcode binaries in the future, add the following to the Makefile of your romhack, after the section starting with build/data/%.o (i.e. two lines after that, with a blank line before and after): build/data/rsp.rodata.o: data/F3DEX3_X.code data/F3DEX3_X.data. It is not a mistake that this new line you are adding won't have a second indented line after it; it is like the message_data_static lines below that. This will tell make to rebuild rsp.rodata.o, which includes the microcode binaries, whenever they are changed.
• Clean and build your romhack (make clean, make).
• Test your romhack and confirm that everything works as intended.
• Make as many of the "Recommended changes" listed below as possible.
• If you start using new features in F3DEX3, make the "Changes required for new features" listed below.

Required Changes

Both OoT and SM64:

• In any place where your game creates a viewport (whether statically or dynamically) (search for Vp case-sensitive, SPViewport, and G_MAXZ), change the maximum Z value from G_MAXZ to G_NEW_MAXZ and negate the Y scale. For more information, see the comment next to G_MAXZ in the GBI. Note that your romhack codebase may have the constant hardcoded (usually as 511 which is supposed to be (G_MAXZ/2)), instead of actually writing an expression containing G_MAXZ; you need to change these too, there are several of these in SM64. Fortunately, it is easy to notice if you have failed to update a Y scale, as anything drawn using that viewport will be upside down.
• Remove uses of internal GBI features which have been removed in F3DEX3 (see @ref compatibility for full list). In OoT, the only changes needed are:
  • In src/code/ucode_disas.c, remove the switch statement cases for G_LINE3D, G_MW_CLIP, G_MV_MATRIX, G_MVO_LOOKATX, G_MVO_LOOKATY, and G_MW_PERSPNORM.
  • In src/libultra/gu/lookathil.c, remove the lines which set the col, colc, and pad fields.
  • As mentioned above, in each place G_MAXZ is used, a compiler error will be generated; negate the Y scale in each related viewport and change the Z scale and offset to use G_NEW_MAXZ.
• Change your game engine lighting code to set the type (formerly pad1) field to 0 in the initialization of any directional light (Light_t and derived structs like Light or Lightsn). This change is required because otherwise garbage nonzero values may be put in this byte, which was a padding byte for a non-point-light microcode but is used to identify the light as point or directional in a point light microcode.
  • The change needed in OoT is: in src/code/z_lights.c, in Lights_BindPoint, Lights_BindDirectional, and Lights_NewAndDraw, set l.type to 0 right before setting l.col.
• If your game already had point lighting, use ENABLE_POINT_LIGHTS instead of G_LIGHTING_POSITIONAL to indicate that point lights are currently active. (Static uses of G_LIGHTING_POSITIONAL in display lists need not be removed as this bit is ignored.)

SM64 only:

• If you are using the vanilla lighting system where light directions are always fixed, the vanilla permanent light direction of {0x28, 0x28, 0x28} must be changed to {0x49, 0x49, 0x49}, or everything will be too dark. The former vector is not properly normalized, but F3D through F3DEX2 normalize light directions in the microcode, so it doesn't matter with those microcodes. The two lighting codepaths in F3DEX3 treat light directions and vertex normals differently: the fast one works like F3DEX2, but the slow one normalizes vertex normals after transforming them and does not modify light directions. Thus in this case, the light directions must already be normalized.
• Matrix stack fix (world space lighting / view matrix in VP instead of in M) is basically required. If you really want camera space lighting, use matrix stack fix, transform the fixed camera space light direction by V inverse each frame, and send that to the RSP.

Recommended Changes (Non-Lighting)

• Clean up any code using the deprecated, hacky SPLookAtX and SPLookAtY to use SPLookAt instead (this is only a few lines change). Also remove any code which writes SPClipRatio or SPForceMatrix--these are now no-ops, so you might as well not write them.
• Avoid using G_MTX_MUL and G_MTX_PUSH in SPMatrix, and SPPopMatrix*, for performance and accuracy reasons. See the GBI for more information. If these are only used in a couple non-critical places such as for GUIs, that's okay.
• Re-export as many display lists (scenes, objects, skeletons, etc.) as possible with fast64 set to F3DEX3 mode, to take advantage of the substantially larger vertex buffer (and eventually when supported by community tools, the triangle packing commands and "hints" system).
• #define REQUIRE_SEMICOLONS_AFTER_GBI_COMMANDS (at the top of, or before including, the GBI) for a more modern, OoT-style codebase where uses of GBI commands require semicolons after them. SM64 omits the semicolons sometimes, e.g. gSPDisplayList(gfx++, foo) gSPEndDisplayList(gfx++);. If you are using -Wpedantic, using this define is required.
• Once everything in your romhack is ported to F3DEX3 and everything is stable, #define NO_SYNCS_IN_TEXTURE_LOADS (at the top of, or before including, the GBI) and fix any crashes or graphical issues that arise. Display lists exported from fast64 already do not contain these syncs, but vanilla display lists or custom ones using the texture loading multi-command macros do. Disabling the syncs saves a few percent of RDP cycles for each material setup; what percentage this is of the total RDP time depends on how many triangles are typically drawn between each material change. For more information, see the GBI documentation near this define.

Recommended Changes (Lighting)

• Change your game engine lighting code to load all lights in one DMA transfer with SPSetLights, instead of one-at-a-time with repeated SPLight commands. Note that if you are using a pointer (dynamically allocated) rather than a direct variable (statically allocated), you need to dereference it; see the docstring for this macro in the GBI.
• If you still need to use SPLight somewhere after this, use SPLight only for directional / point lights and use SPAmbient for ambient lights. Directional / point lights are 16 bytes and ambient are 8, and the first 8 bytes are the same for both types, so normally it's okay to use SPLight instead of SPAmbient to write ambient lights too. However, the memory space reserved for lights in the microcode is 16*9+8 bytes, so if you have 9 directional / point lights and then use SPLight to write the ambient light, it will overflow the buffer by 8 bytes and corrupt memory.
• Once you have made the above change for SPAmbient, increase the maximum number of lights in your engine from 7 to 9.
• Consider setting lights once before rendering a scene and all actors, rather than setting lights before rendering each actor. OoT does the latter to emulate point lights in a scene with a directional light recomputed per actor. You can now just send those to the RSP as real point lights, regardless of whether the display lists are vanilla or new.
• If your game already had point lighting, note that the point light kc, kl, and kq factors have been changed, so you will need to redesign how game engine light parameters (e.g. "light radius") map to these parameters.

Changes Required for New Features

Each of these changes is required if you want to use the respective new feature, but is not necessary if you are not using it.

• For Fresnel and specular lighting: Whenever your code sends camera properties to the RSP (VP matrix, viewport, etc.), also send the camera world position to the RSP with SPCameraWorld. For OoT, this is not trivial because the game rendering creates and sets the view matrix in the main DL, then renders the game contents, then updates the camera, and finally retroactively modifies the view matrix at the beginning of the main DL. See the code in @ref camera.
• For specular lighting: Set the size field of any Light_t and PosLight_t to an appropriate value based on the game engine parameters for that light.
• For the occlusion plane: Bring the code from cpu/occlusionplane.c into your game and follow the included instructions.
• For the performance counters: See @ref counters.