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Document a bug in EnRacedog and add some diagrams to EnRacedog_IsOverFinishLine (#1288)

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* Document a bug in EnRacedog and add some diagrams to EnRacedog_IsOverFinishLine

* Mention floating-point precision in the comment
This commit is contained in:
Tom Overton
2023-06-17 17:33:58 -04:00
committed by GitHub
parent e73034f8cd
commit 5800c4669f
1 changed files with 21 additions and 0 deletions
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src/overlays/actors/ovl_En_Racedog/z_en_racedog.c
+21
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@@ -628,13 +628,28 @@ s32 EnRacedog_IsOverFinishLine(EnRacedog* this, Vec2f* finishLineCoordinates) {
// frontPointsCrossProduct is positive if the dog is to the left of the line formed by the front points
// crossProductTemp is positive if the dog is above the line formed by the bottom points
// This is checking that the dog within the region defined by front and bottom lines like so:
// |
// X | Front
// |
// --------
// Bottom
frontPointsCrossProduct = ((xDistToTopFront * zDistToBottomFront) - (xDistToBottomFront * zDistToTopFront));
crossProductTemp = (((xDistToBottomFront * zDistToBottomBack) - (xDistToBottomBack * zDistToBottomFront)));
//! @bug If any dog is precisely (with floating-point precision) on top of the line formed by the front points,
//! then frontPointsCrossProduct will be zero. This will cause this multiplication (and all future multiplications)
//! to be zero, which will make this function think the dog has crossed the finish line. The line formed by the
//! front points extends throughout the entire racetrack, so a dog can trigger this when they're not even close to
//! the actual finish line, causing them to finish the race incredibly early.
if (frontPointsCrossProduct * crossProductTemp < 0.0f) {
return false;
}
// crossProductTemp is positive if the dog is to the right of the line formed by the back points
// This is checking that the dog within the region defined by front and back lines like so:
// | |
// Back | X | Front
// | |
frontPointsCrossProduct = ((xDistToTopFront * zDistToBottomFront) - (xDistToBottomFront * zDistToTopFront));
crossProductTemp = ((xDistToBottomBack * zDistToTopBack) - (xDistToTopBack * zDistToBottomBack));
if (frontPointsCrossProduct * crossProductTemp < 0.0f) {
@@ -642,6 +657,12 @@ s32 EnRacedog_IsOverFinishLine(EnRacedog* this, Vec2f* finishLineCoordinates) {
}
// crossProductTemp is positive if the dog is below the line formed by the top points
// This is checking that the dog within the region defined by front and top lines like so:
// Top
// --------
// |
// X | Front
// |
frontPointsCrossProduct = ((xDistToTopFront * zDistToBottomFront) - (xDistToBottomFront * zDistToTopFront));
crossProductTemp = ((xDistToTopBack * zDistToTopFront) - (xDistToTopFront * zDistToTopBack));
if (frontPointsCrossProduct * crossProductTemp < 0.0f) {