[Fixed] for "off-by-1" bug when sampling "baked" curve data towards the end of the curve.

[Fixed] Failing test "[Curve] Custom curve with free tangents" by setting the curve's `bake_resolution` to 11.
[Fixed] test messages in "[Curve] Custom curve with free tangents" to match sample offset used in each test
[Added] New test "[Curve] Straight line offset test" in response to pull request feedback.
Update tests/scene/test_curve.h

Co-authored-by: kleonc <[email protected]>

scene/resources/curve.cpp

@@ -452,7 +452,7 @@ void Curve::bake() {
 	_baked_cache.resize(_bake_resolution);
 
 	for (int i = 1; i < _bake_resolution - 1; ++i) {
-		real_t x = i / static_cast<real_t>(_bake_resolution);
+		real_t x = i / static_cast<real_t>(_bake_resolution - 1);
 		real_t y = sample(x);
 		_baked_cache.write[i] = y;
 	}
@@ -489,7 +489,7 @@ real_t Curve::sample_baked(real_t p_offset) const {
 	}
 
 	// Get interpolation index
-	real_t fi = p_offset * _baked_cache.size();
+	real_t fi = p_offset * (_baked_cache.size() - 1);
 	int i = Math::floor(fi);
 	if (i < 0) {
 		i = 0;

tests/scene/test_curve.h

@@ -62,6 +62,7 @@ TEST_CASE("[Curve] Custom curve with free tangents") {
 	curve->add_point(Vector2(0.25, 1));
 	curve->add_point(Vector2(0.5, 0));
 	curve->add_point(Vector2(0.75, 1));
+	curve->set_bake_resolution(11);
 
 	CHECK_MESSAGE(
 			Math::is_zero_approx(curve->get_point_left_tangent(0)),
@@ -82,41 +83,41 @@ TEST_CASE("[Curve] Custom curve with free tangents") {
 
 	CHECK_MESSAGE(
 			Math::is_zero_approx(curve->sample(-0.1)),
-			"Custom free curve should return the expected value at offset 0.1.");
+			"Custom free curve should return the expected value at offset -0.1.");
 	CHECK_MESSAGE(
 			curve->sample(0.1) == doctest::Approx((real_t)0.352),
 			"Custom free curve should return the expected value at offset 0.1.");
 	CHECK_MESSAGE(
 			curve->sample(0.4) == doctest::Approx((real_t)0.352),
-			"Custom free curve should return the expected value at offset 0.1.");
+			"Custom free curve should return the expected value at offset 0.4.");
 	CHECK_MESSAGE(
 			curve->sample(0.7) == doctest::Approx((real_t)0.896),
-			"Custom free curve should return the expected value at offset 0.1.");
+			"Custom free curve should return the expected value at offset 0.7.");
 	CHECK_MESSAGE(
 			curve->sample(1) == doctest::Approx(1),
-			"Custom free curve should return the expected value at offset 0.1.");
+			"Custom free curve should return the expected value at offset 1.");
 	CHECK_MESSAGE(
 			curve->sample(2) == doctest::Approx(1),
-			"Custom free curve should return the expected value at offset 0.1.");
+			"Custom free curve should return the expected value at offset 2.");
 
 	CHECK_MESSAGE(
 			Math::is_zero_approx(curve->sample_baked(-0.1)),
-			"Custom free curve should return the expected baked value at offset 0.1.");
+			"Custom free curve should return the expected baked value at offset -0.1.");
 	CHECK_MESSAGE(
 			curve->sample_baked(0.1) == doctest::Approx((real_t)0.352),
 			"Custom free curve should return the expected baked value at offset 0.1.");
 	CHECK_MESSAGE(
 			curve->sample_baked(0.4) == doctest::Approx((real_t)0.352),
-			"Custom free curve should return the expected baked value at offset 0.1.");
+			"Custom free curve should return the expected baked value at offset 0.4.");
 	CHECK_MESSAGE(
 			curve->sample_baked(0.7) == doctest::Approx((real_t)0.896),
-			"Custom free curve should return the expected baked value at offset 0.1.");
+			"Custom free curve should return the expected baked value at offset 0.7.");
 	CHECK_MESSAGE(
 			curve->sample_baked(1) == doctest::Approx(1),
-			"Custom free curve should return the expected baked value at offset 0.1.");
+			"Custom free curve should return the expected baked value at offset 1.");
 	CHECK_MESSAGE(
 			curve->sample_baked(2) == doctest::Approx(1),
-			"Custom free curve should return the expected baked value at offset 0.1.");
+			"Custom free curve should return the expected baked value at offset 2.");
 
 	curve->remove_point(1);
 	CHECK_MESSAGE(
@@ -218,6 +219,16 @@ TEST_CASE("[Curve] Custom curve with linear tangents") {
 			"Custom free curve should return the expected baked value at offset 0.7 after removing point at invalid index 10.");
 }
 
+TEST_CASE("[Curve] Straight line offset test") {
+	Ref<Curve> curve = memnew(Curve);
+	curve->add_point(Vector2(0, 0));
+	curve->add_point(Vector2(1, 1));
+
+	CHECK_MESSAGE(
+			curve->sample_baked(1.0 - (0.5 / curve->get_bake_resolution())) != curve->sample_baked(1),
+			"Straight line curve should return different baked values at offset 1 vs offset (1 - 0.5 / bake resolution) .");
+}
+
 TEST_CASE("[Curve2D] Linear sampling should return exact value") {
 	Ref<Curve2D> curve = memnew(Curve2D);
 	real_t len = 2048.0;