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VCRUISE: Update comments to clarify how circuit puzzle AI works.

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This commit is contained in:
elasota 2023-05-25 01:12:09 -04:00
parent f0eabd1952
commit 2cf068efb1
1 changed files with 10 additions and 16 deletions
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26
engines/vcruise/circuitpuzzle.cpp
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@ -329,23 +329,18 @@ CircuitPuzzle::CircuitPuzzle(int layout) : _havePreviousAction(false) {
}
bool CircuitPuzzle::executeAIAction(Common::RandomSource &randomSource, Common::Point &outCoord, CellDirection &outBlockDirection) {
// I've attempted to figure out what Schizm's AI algorithm does to no avail.
// Don't know exactly what algorithm Schizm uses, we use something that approximates the original
// pretty well most of the time:
// - Identify all connection paths that are tied for the fewest number of new connections required to win.
// - Enumerate all open connections on those paths.
// - If the previous move blocked a horizontal connection (i.e. with a vertical barrier), prioritize
// connections on the same X coordinate as that block.
// - Block a random connection from the candidates.
//
// What we do, which is approximately what Schizm's AI does, is find all paths tied for the shortest path to the goal
// and randomly block a point on that path. Sometimes Schizm's AI will fail to a 1-distance spot, and sometimes it will fail
// to opportunistically block a spot that would cause the AI to immediatley win, so this isn't a perfect reproduction of it,
// but it is very close.
// There seem to be times that Schizm doesn't do this. In particular, Schizm will (rarely) fail to block
// a connection even if it's the only connection that will immediately win the puzzle for the player.
//
// We solve this as a series of 2 flood fills:
// - First, each point is assigned a maximum distance score
// - Next, all points connected to the start point (0,0) are assigned a score of 0.
// - Next, all points are progressively expanded to determine the minimum number of
// connections needed to reach the point.
// - If the end point is assigned a score, then flood fill stops and the backtrace phase
// begins. The backtrace phase collects all links starting from the end that link to
// another point with 1 less move required to reach it.
// - A random link is chosen as the AI move.
// It also doesn't prioritize making moves that will immediately win for the AI.
CircuitPuzzleAIEvaluator evaluator;
computeStepsToReach(evaluator);
@ -442,7 +437,6 @@ bool CircuitPuzzle::executeAIAction(Common::RandomSource &randomSource, Common::
// All potential blocks are now on the shortest path.
// Try to mimic some of the AI behavior of Schizm to form wall advances.
// The highest-priority move is one that runs parallel to the previous move.
// If no such move exists, then a move that shares a corner is priority.
uint selectedBlock = 0;
if (numPotentialBlocks > 1) {
uint blockQualities[kMaxLinks];