# Difference between revisions of "User:Nightmareci"

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# Further processing after gravity (processing will come back to 2. if the piece hasn't locked) | # Further processing after gravity (processing will come back to 2. if the piece hasn't locked) | ||

In the above, the line "Gcount = Gspeed % 256" may appear curious, as all Internal Gravity values in the TGM series are either <256 or an even multiple of 256, but it's purpose is to properly support gravity speeds such as 4.5G; none of the TGM games have gravity like this, but this makes this description more general. | In the above, the line "Gcount = Gspeed % 256" may appear curious, as all Internal Gravity values in the TGM series are either <256 or an even multiple of 256, but it's purpose is to properly support gravity speeds such as 4.5G; none of the TGM games have gravity like this, but this makes this description more general. | ||

In ANSI C, one can use bitwise operators instead of the division and modulo (%) operators, because 256 is a power of 2; a simple example follows: | In ANSI C, one can use bitwise operators instead of the division and modulo (%) operators, because 256 is a power of 2; a simple example follows: | ||

<pre> | <pre> |

## Revision as of 00:26, 18 February 2009

## Definitions

In this page, the very top row is row number 0, the row below the top row is row number 1, and so on, until 20 (TGM1 has 20 visible rows + 1 vanish zone row).

## Tetris The Grand Master

Some of the following information may not be consistent with other wiki pages; where this applies, simply ignore the information elsewhere in the wiki. Corrections to this information by others are only accepted if supported by examples. Information here is still work in progress.

### Gravity

Directly from Tetris The Grand Master, here is the gravity curve:

Level | Interal Gravity (1/256 G) |
Level | Internal Gravity (1/256 G) |
---|---|---|---|

0 | 4 | 220 | 32 |

30 | 6 | 230 | 64 |

35 | 8 | 233 | 96 |

40 | 10 | 236 | 128 |

50 | 12 | 239 | 160 |

60 | 16 | 243 | 192 |

70 | 32 | 247 | 224 |

80 | 48 | 251 | 256 (1G) |

90 | 64 | 300 | 512 (2G) |

100 | 80 | 330 | 768 (3G) |

120 | 96 | 360 | 1024 (4G) |

140 | 112 | 400 | 1280 (5G) |

160 | 128 | 420 | 1024 (4G) |

170 | 144 | 450 | 768 (3G) |

200 | 4 | 500 | 5120 (20G) |

In the following, Gcount is the current Gravity Count; Gspeed is the Gravity Speed, and is equal to one of the Internal Gravity entries in the above table. All values can be represented with unsigned integers, as no negative values ever appear. All division has the fractional part truncated, as in ISO C (60/256 = 0, 252/256 = 0, 260/256 = 1).

On the first frame of piece display, a soft drop input is simply ignored, so, for example, some variable representing whether soft drop "is pressed" or "not pressed" would be set to "not pressed" on the first frame. The second frame and later can have a soft drop input set, for example, as "is pressed"; this processing of input occurs outside this description.

- Preparation for the pieces' first displayed frame (such as during ARE):
- Gcount = Gspeed % 256
- Gspeed is set to the appropriate value for the current level
- Attempt to place the piece in row number 1 + Gspeed / 256, higher if necessary

- Every frame this piece is displayed:
- If soft drop is pressed:
- If Gspeed < 256:
- Attempt to drop one line

- If the piece has blocks beneath it now:
- Lock the piece

- Go to 3.

- If Gspeed < 256:
- If there are blocks below this piece:
- Set Gcount to Gspeed

- If Gcount is greater than or equal to 256:
- Attempt to drop Gcount / 256 lines
- Set Gcount to the remainder of Gcount / 256 (in C, this would be "Gcount %= 256")

- Increase Gcount by Gspeed
- Go to 3.

- If soft drop is pressed:
- Further processing after gravity (processing will come back to 2. if the piece hasn't locked)

In the above, the line "Gcount = Gspeed % 256" may appear curious, as all Internal Gravity values in the TGM series are either <256 or an even multiple of 256, but it's purpose is to properly support gravity speeds such as 4.5G; none of the TGM games have gravity like this, but this makes this description more general.

In ANSI C, one can use bitwise operators instead of the division and modulo (%) operators, because 256 is a power of 2; a simple example follows:

placeInRow = 1 + Gspeed >> 8; // equivalent to 'placeInRow = 1 + Gspeed / 256;' linesToDrop = Gcount >> 8; // equivalent to 'linesToDrop = Gcount / 256;' Gcount &= 255; // equivalent to 'Gcount %= 256;'

On more limited systems where division and modulo would be noticeably slow, using bitwise operators this way can significantly improve performance. Because only positive integers appear in these expressions, ANSI C guarantees these expressions are equivalent, on implementations following ANSI C. On very limited systems (such as the NES), these would be easy to translate to assembly.