Cutscenes and bug hunting

Prince of Persia

The lasts weeks i have been bussy fixing some bugs ( thanks to David from the Princed forums for his extensive testing) and implementing new features. This is the changelog for the new version:

[BUG] Pillar and arch tiles do not act as space
[BUG] Tapestries tiles do not act as barriers
[BUG] Prince sprite is cropped when falling after a jump up
[BUG] Prince sprite cropped incorrectly on exit level animation
[BUG] Upper level loose board do not fall when prince jumps up
[BUG] Potion bubbles has no colors
[BUG] Large potion bubbles shows at incorrect position
[REFACTOR] Redesigned game manager to separate level logic and level design
[REFACTOR] Implemented a class for every tile object
[FEATURE] Chopper implemented
[FEATURE] Title screens, credits, intro cutscene and in-game cutscenes implemented.
cutscene

Image from intro cutscene

From the list, the most noticiable feature is the implementation of the cutscenes. In preparation for the development of the guards AI i decided to investigate how to implement the behaviour of the actors in the cutscenes between levels (princess and vizier scenes). At the end i finally developed a very simple virtual machine, with a reduced instruction set, that let me program the behaviour of the actors for every scene. So, the next script represent the intro cutscene of the game:

{ "i": "ADD_ACTOR", "p1": 0, "p2": 5, "p3": 62, "p4": 167, "p5": -1 },
{ "i": "ADD_ACTOR", "p1": 1, "p2": 6, "p3": 140, "p4": 167, "p5": -1 },
{ "i": "START" },
{ "i": "ACTION", "p1": 0, "p2": "stand" },
{ "i": "ACTION", "p1": 1, "p2": "stand" },
{ "i": "WAIT", "p1": 20 },
{ "i": "ACTION", "p1": 0, "p2": "alert" },
{ "i": "WAIT", "p1": 6 },
{ "i": "ACTION", "p1": 1, "p2": "walk" },
{ "i": "WAIT", "p1": 6 },
{ "i": "ACTION", "p1": 1, "p2": "stop" },
{ "i": "WAIT", "p1": 20 },
{ "i": "ACTION", "p1": 1, "p2": "walk" },
{ "i": "WAIT", "p1": 30 },
{ "i": "ACTION", "p1": 1, "p2": "stop" },
{ "i": "WAIT", "p1": 35 },
{ "i": "ACTION", "p1": 1, "p2": "raise" },
{ "i": "WAIT", "p1": 1 },
{ "i": "ACTION", "p1": 0, "p2": "stepback" },
{ "i": "WAIT", "p1": 10 },
{ "i": "EFFECT" },
{ "i": "ADD_OBJECT", "p1": 0, "p2": 0, "p3": 152, "p4": 141 },
{ "i": "WAIT", "p1": 25 },
{ "i": "ACTION", "p1": 1, "p2": "exit" },
{ "i": "START_OBJECT", "p1": 0 },
{ "i": "WAIT", "p1": 43 },
{ "i": "ACTION", "p1": 0, "p2": "slump" },
{ "i": "WAIT", "p1": 20 },
{ "i": "END" } ]

The script is JSON formatted, and every line is an instruction. For example, the first instruccion adds on screen an actor (the princess has code 5 in-game) on position (62,167) and facing left (-1). So, every cutscene has an script like this, and is very easy to write them. The cutscene manager implements a very simple virtual machine that reads an instruction every tick and execute it.

This system is also suitable for script the special events of the game ( gate closed on first level, mouse help, shadow on mirror level, falling floors on lasts levels, etc…) and for the guards AI i’m still undecided: perhaps i will use the same method (an script for every guard type) or perhaps i will try some sort of state machine like machina.js

Well, enough for now. You can try the last version here. Have fun!!

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One thought on “Cutscenes and bug hunting

  1. Would it be possible to add hardcore 4D PoP levels in the future — https://archive.org/details/msdos_4D_Prince_of_Persia_1994 ?

    Have you heard about CRT shaders, e.g. http://www.zachstronaut.com/posts/2012/08/17/webgl-fake-crt-html5.html ? One can get this retro feeling even when playing on a modern LCD screen.

    Do you plan to support CGA and EGA modes of PoP — http://www.welovedosgames.net/article/Comparison%20between%20CGA,%20EGA%20and%20VGA%20graphics/ ? It would be nice. Changing modes is like playing a new game each time. 🙂

    Keep up good work!

    Like

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