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fix(physics): restore standard tangent sign response

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The left relative slingshot probe proved the spin projection, but its geometry
did not distinguish the sign rule. A stopped-Wine probe on symmetric record 72
did: the binary uses the standard dot-product tangent for both spin and the
opposing direction of the current tangential response. The earlier
swapped-component interpretation happened to agree for vertical walls and a
centered circle but selected the wrong sign on the right slingshot.

Use `tv=(vx*nx+vy*ny)/length`, update spin with
`tv*0.02*response_tangent`, and apply
`-sign(tv)*abs(normal_velocity)*response_tangent`, retaining the binary's
negative direction when tv is zero. Seal record 72's exact position, velocity,
and `+5.46` Real48 spin in C and Rust. Keep the two-minute autoplay assertion
focused on actual launch, press/release, target, bumper, and finite-state
activity after the corrected trajectory.

Test Plan:
- stopped Wine 11.15 record-72 injection/trace -- matched position, velocity, and spin
- `cargo test --workspace --all-targets --all-features` -- 124 passed
- `cargo clippy --workspace --all-targets --all-features -- -D warnings` -- passed
- `bash original/tools/test_reconstructed_c.sh` -- passed
- `python3 original/tools/audit_reconstruction.py --require-complete` -- passed with zero incomplete or unclassified units
- `rumdl check --flavor commonmark RECONSTRUCTION.md CHANGELOG.md` -- passed
- `git diff --cached --check` -- passed
This commit is contained in:
ddidderr
2026-08-23 20:33:20 +02:00
parent f79652bc9f
commit 23195cb9d1
9 changed files with 124 additions and 68 deletions
Download Patch File Download Diff File Expand all files Collapse all files
original/reconstructed/tdkpin_physics.c
+8 -30
View File
@@ -191,23 +191,7 @@ static int32_t normal_velocity_checked(
velocity_x, velocity_y, normal_x, normal_y, normal_length);
}
static int32_t tangent_direction_unchecked(
int32_t velocity_x,
int32_t velocity_y,
BorlandReal48 normal_x,
BorlandReal48 normal_y,
int32_t normal_length)
{
return negate_wrap(borland_real48_round_to_i32(borland_real48_divide(
borland_real48_add(
borland_real48_multiply(
borland_i32_to_real48(velocity_x), normal_y),
borland_real48_multiply(
borland_i32_to_real48(velocity_y), normal_x)),
borland_i32_to_real48(normal_length))));
}
static int32_t spin_velocity_unchecked(
static int32_t tangent_velocity_unchecked(
int32_t velocity_x,
int32_t velocity_y,
BorlandReal48 normal_x,
@@ -943,16 +927,9 @@ static void apply_collision_response(
tdkpin_add_score_from_caller_frame(caller_bp, candidate->score);
}
int32_t length = candidate_normal_length(candidate);
/* Raw 1000:ef19..f16a keeps the contact-direction and spin projections
* separate. The swapped-component value selects the sign of the current
* tangential response; the standard dot product updates retained spin. */
int32_t tangent_direction = tangent_direction_unchecked(
motion->velocity_x,
motion->velocity_y,
candidate->normal_x,
candidate->normal_y,
length);
int32_t spin_projection = spin_velocity_unchecked(
/* Raw 1000:ef19..f16a uses the standard dot-product tangent both to
* oppose the current tangential motion and to update retained spin. */
int32_t tangent_velocity = tangent_velocity_unchecked(
motion->velocity_x,
motion->velocity_y,
candidate->normal_x,
@@ -961,7 +938,7 @@ static void apply_collision_response(
BorlandReal48 spin_delta = borland_real48_multiply(
borland_real48_multiply(
borland_i32_to_real48(spin_projection),
borland_i32_to_real48(tangent_velocity),
g_real48_point_zero_two),
candidate->response_tangent);
BorlandReal48 discarded = borland_real48_divide(
@@ -974,7 +951,8 @@ static void apply_collision_response(
BorlandReal48 tangent_response = borland_real48_multiply(
borland_i32_to_real48(absolute_wrap(candidate->normal_velocity)),
candidate->response_tangent);
if (tangent_direction < 0) {
tangent_response = negate_real48(tangent_response);
if (tangent_velocity < 0) {
tangent_response = negate_real48(tangent_response);
}
int32_t projection = borland_real48_round_to_i32(borland_real48_add(
@@ -982,7 +960,7 @@ static void apply_collision_response(
borland_real48_multiply(motion->spin, g_real48_point_four),
borland_real48_divide(
borland_real48_multiply(
borland_i32_to_real48(absolute_wrap(tangent_direction)),
borland_i32_to_real48(absolute_wrap(tangent_velocity)),
discarded),
borland_i32_to_real48(motion->speed))),
tangent_response));