====== F3DDKR Microcode ======

F3DDKR (unofficial name) is a modified version of the [[super_mario_64:fast3d_display_list_commands|Fast3D microcode]]. It was created by Rareware for the game Diddy Kong Racing.

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===== Changes from Fast3D =====

  - The commands [[super_mario_64:fast3d_display_list_commands#beg_culldl|G_CULLDL]], [[super_mario_64:fast3d_display_list_commands#bfg_tri1|G_TRI1]], and [[super_mario_64:fast3d_display_list_commands#bdg_popmtx|G_POPMTX]] were removed, and are now NOPS (No operations).
  - Triangles are drawn in batches; up to 16 triangles per batch.
  - The number of vertices was increased from 16 to 24.
  - The vertex structure is smaller, being only 10 bytes per vertex instead of 16.
  - UV coordinates are per-face instead of per-vertex.
  - The lighting overlay was removed. Dynamic lighting & environment mapping for objects are calculated on the CPU.
  - The matrix stack has been removed; there are now only 3 matrices at fixed offsets.
  - The number of segment banks has been reduced from 16 to 8
  - Mipmapping cannot be done, due to some changes in the triangle setup routine.

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===== Structures =====

==== Vertex (10 bytes) ====

''[<color red>XX XX</color>] [<color green>YY YY</color>] [<color cyan>ZZ ZZ</color>] [<color pink>RR</color>] [<color lightgreen>GG</color>] [<color lightblue>BB</color>] [<color lightgray>AA</color>]''

| <color red>XXXX</color> |    short    | Position on X axis |
| <color green>YYYY</color> |    short    | Position on Y axis |
| <color cyan>ZZZZ</color> |    short    | Position on Z axis |
| <color pink>RR</color> |    ubyte    | Red color channel |
| <color lightgreen>GG</color> |    ubyte    | Green color channel |
| <color lightblue>BB</color> |    ubyte    | Blue color channel |
| <color lightgray>AA</color> |     ubyte     | Alpha (Transparency) |

==== Triangle Face (16 bytes) ====

''[<color lightgray>BF</color>] [<color red>V0</color>] [<color green>V1</color>] [<color cyan>V2</color>] [<color orange>U1U1</color>] [<color #AA88DD>V1V1</color>] [<color pink>U2U2</color>] [<color lightgreen>V2V2</color>] [<color lightblue>U3U3</color>] [<color lightyellow>V3V3</color>]''

| <color lightgray>BF</color> | ubyte | 0x40 = Draw the backface of the triangle, 0x00 = Cull backface |
| <color red>V0</color> | ubyte | First vertex index |
| <color green>V1</color> | ubyte | Second vertex index |
| <color cyan>V2</color> | ubyte | Third vertex index |
| <color orange>U1U1</color> |    short    | Texture coordinate on the U axis for the first vertex |
| <color #AA88DD>V1V1</color> |    short    | Texture coordinate on the V axis for the first vertex |
| <color pink>U2U2</color> |    short    | Texture coordinate on the U axis for the second vertex |
| <color lightgreen>V2V2</color> |    short    | Texture coordinate on the V axis for the second vertex |
| <color lightblue>U3U3</color> |    short    | Texture coordinate on the U axis for the third vertex |
| <color lightyellow>V3V3</color> |    short    | Texture coordinate on the V axis for the third vertex |

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===== Added/Modified Commands =====

==== 01: G_MTX ====
Loads a matrix from a segmented address.

''01 [<color pink>II</color>] 00 40 [<color #AA88DD>AA AA AA AA</color>]''

| <color pink>I</color> | Index in the matrix array within DMEM. 0x00, 0x40, or 0x80 |
| <color #AA88DD>A</color> | Segmented address of vectors |

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==== 04: G_VTX ====
Loads up to 24 vertices from a segment address.

''04 [<color pink>N</color><color lightgreen>O</color>] [<color lightblue>II II</color>] [<color #AA88DD>SS SS SS SS</color>]''

| <color pink>N</color><color lightgreen>O</color> | Upper 5 bits = Number of vertices - 1, Lower 3 bits = Offset within vertex struct to start at |
| <color lightblue>I</color> | (Where to start writing vertices inside the vertex buffer) * 2 |
| <color #AA88DD>S</color> | Segmented address to load vertices from |

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==== 05: G_TRIN ====
Draws a batch of triangles from a segmented address. Up to 16 triangles can be drawn at once.

''05 [<color pink>N</color>] [<color lightgreen>T</color>] [<color lightblue>LL LL</color>] [<color #AA88DD>SS SS SS SS</color>]''

| <color pink>N</color> | Number of triangles - 1 |
| <color lightgreen>T</color> | 0x01 = Enable texture, 0x00 = Disable texture |
| <color lightblue>L</color> | Length of data to write in bytes ((<color pink>N</color>+1)*16) |
| <color #AA88DD>S</color> | Segmented address to load triangle data from |

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==== 07: G_DMADL ====
DMAs a fixed-size display list from RDRAM and outputs the commands directly to the RDP. This is used by the game engine to load textures for models. 

''07 [<color pink>NN</color>] [<color lightblue>LL LL</color>] [<color #AA88DD>SS SS SS SS</color>]''

| <color pink>N</color> | Number of commands |
| <color lightblue>L</color> | Length of data in bytes (N*8) |
| <color #AA88DD>S</color> | Segmented address to the display list. |

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==== B5: G_SETPERSPNORM ====
Sets the perspective normal value. Might be unused.

''B5 00 00 00 [<color pink>PP PP</color>] 00 00''

| <color pink>P</color> | PERSPNORM value |

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==== BC: G_MOVEWORD ====
The format is still the same as Fast3D, but two indices have been changed:

| <color #22b14c>G_MW_BILLBOARD</color> | 0x02 | 0x01 = billboarding enabled, 0x00 = disabled |
| <color #22b14c>G_MW_MVMATRIX</color> | 0x0A | Specifies the index of the modelview matrix. |

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===== References =====
  * https://git.libretro.com/libretro/mupen64plus-libretro-nx/-/blob/develop/GLideN64/src/uCodes/F3DDKR.cpp