Switch to precise lerp. (#548)

bitshifter · web-flow · commit 7cc4dcef03e4 · 2024-08-13T23:57:40.000+12:00
Reviving #278, fixes #275.
diff --git a/codegen/templates/vec.rs.tera b/codegen/templates/vec.rs.tera
@@ -1867,7 +1867,7 @@ impl {{ self_t }} {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: {{ scalar_t }}) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/coresimd/vec3a.rs b/src/f32/coresimd/vec3a.rs
@@ -726,7 +726,7 @@ impl Vec3A {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/coresimd/vec4.rs b/src/f32/coresimd/vec4.rs
@@ -713,7 +713,7 @@ impl Vec4 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/neon/vec3a.rs b/src/f32/neon/vec3a.rs
@@ -770,7 +770,7 @@ impl Vec3A {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/neon/vec4.rs b/src/f32/neon/vec4.rs
@@ -747,7 +747,7 @@ impl Vec4 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/scalar/vec3a.rs b/src/f32/scalar/vec3a.rs
@@ -769,7 +769,7 @@ impl Vec3A {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/scalar/vec4.rs b/src/f32/scalar/vec4.rs
@@ -827,7 +827,7 @@ impl Vec4 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/sse2/vec3a.rs b/src/f32/sse2/vec3a.rs
@@ -769,7 +769,7 @@ impl Vec3A {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/sse2/vec4.rs b/src/f32/sse2/vec4.rs
@@ -755,7 +755,7 @@ impl Vec4 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/vec2.rs b/src/f32/vec2.rs
@@ -692,7 +692,7 @@ impl Vec2 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/vec3.rs b/src/f32/vec3.rs
@@ -759,7 +759,7 @@ impl Vec3 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/wasm32/vec3a.rs b/src/f32/wasm32/vec3a.rs
@@ -737,7 +737,7 @@ impl Vec3A {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f32/wasm32/vec4.rs b/src/f32/wasm32/vec4.rs
@@ -730,7 +730,7 @@ impl Vec4 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f32) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f64/dvec2.rs b/src/f64/dvec2.rs
@@ -692,7 +692,7 @@ impl DVec2 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f64) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f64/dvec3.rs b/src/f64/dvec3.rs
@@ -759,7 +759,7 @@ impl DVec3 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f64) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/src/f64/dvec4.rs b/src/f64/dvec4.rs
@@ -816,7 +816,7 @@ impl DVec4 {
     #[inline]
     #[must_use]
     pub fn lerp(self, rhs: Self, s: f64) -> Self {
-        self + ((rhs - self) * s)
+        self * (1.0 - s) + rhs * s
     }
 
     /// Moves towards `rhs` based on the value `d`.
diff --git a/tests/vec2.rs b/tests/vec2.rs
@@ -843,6 +843,13 @@ macro_rules! impl_vec2_float_tests {
             assert_approx_eq!($vec2::ZERO, v0.lerp(v1, 0.5));
         });
 
+        glam_test!(test_lerp_big_difference, {
+            let v0 = $vec2::new(-1e30, -1e30);
+            let v1 = $vec2::new(16.0, 16.0);
+            assert_approx_eq!(v0, v0.lerp(v1, 0.0));
+            assert_approx_eq!(v1, v0.lerp(v1, 1.0));
+        });
+
         glam_test!(test_move_towards, {
             let v0 = $vec2::new(-1.0, -1.0);
             let v1 = $vec2::new(1.0, 1.0);
diff --git a/tests/vec3.rs b/tests/vec3.rs
@@ -987,6 +987,13 @@ macro_rules! impl_vec3_float_tests {
             assert_approx_eq!($vec3::ZERO, v0.lerp(v1, 0.5));
         });
 
+        glam_test!(test_lerp_big_difference, {
+            let v0 = $vec3::new(-1e30, -1e30, -1e30);
+            let v1 = $vec3::new(16.0, 16.0, 16.0);
+            assert_approx_eq!(v0, v0.lerp(v1, 0.0));
+            assert_approx_eq!(v1, v0.lerp(v1, 1.0));
+        });
+
         glam_test!(test_move_towards, {
             let v0 = $vec3::new(-1.0, -1.0, -1.0);
             let v1 = $vec3::new(1.0, 1.0, 1.0);
diff --git a/tests/vec4.rs b/tests/vec4.rs
@@ -1124,6 +1124,13 @@ macro_rules! impl_vec4_float_tests {
             assert_approx_eq!($vec4::ZERO, v0.lerp(v1, 0.5));
         });
 
+        glam_test!(test_lerp_big_difference, {
+            let v0 = $vec4::new(-1e30, -1e30, -1e30, -1e30);
+            let v1 = $vec4::new(16.0, 16.0, 16.0, 16.0);
+            assert_approx_eq!(v0, v0.lerp(v1, 0.0));
+            assert_approx_eq!(v1, v0.lerp(v1, 1.0));
+        });
+
         glam_test!(test_move_towards, {
             let v0 = $vec4::new(-1.0, -1.0, -1.0, -1.0);
             let v1 = $vec4::new(1.0, 1.0, 1.0, 1.0);

Original file line number	Diff line number	Diff line change
`@@ -1867,7 +1867,7 @@ impl {{ self_t }} {`
`1867`	`1867`	`#[inline]`
`1868`	`1868`	`#[must_use]`
`1869`	`1869`	`pub fn lerp(self, rhs: Self, s: {{ scalar_t }}) -> Self {`
`1870`		`- self + ((rhs - self) * s)`
	`1870`	`+ self * (1.0 - s) + rhs * s`
`1871`	`1871`	`}`
`1872`	`1872`
`1873`	`1873`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -726,7 +726,7 @@ impl Vec3A {`
`726`	`726`	`#[inline]`
`727`	`727`	`#[must_use]`
`728`	`728`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`729`		`- self + ((rhs - self) * s)`
	`729`	`+ self * (1.0 - s) + rhs * s`
`730`	`730`	`}`
`731`	`731`
`732`	`732`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -713,7 +713,7 @@ impl Vec4 {`
`713`	`713`	`#[inline]`
`714`	`714`	`#[must_use]`
`715`	`715`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`716`		`- self + ((rhs - self) * s)`
	`716`	`+ self * (1.0 - s) + rhs * s`
`717`	`717`	`}`
`718`	`718`
`719`	`719`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -770,7 +770,7 @@ impl Vec3A {`
`770`	`770`	`#[inline]`
`771`	`771`	`#[must_use]`
`772`	`772`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`773`		`- self + ((rhs - self) * s)`
	`773`	`+ self * (1.0 - s) + rhs * s`
`774`	`774`	`}`
`775`	`775`
`776`	`776`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -747,7 +747,7 @@ impl Vec4 {`
`747`	`747`	`#[inline]`
`748`	`748`	`#[must_use]`
`749`	`749`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`750`		`- self + ((rhs - self) * s)`
	`750`	`+ self * (1.0 - s) + rhs * s`
`751`	`751`	`}`
`752`	`752`
`753`	`753`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -769,7 +769,7 @@ impl Vec3A {`
`769`	`769`	`#[inline]`
`770`	`770`	`#[must_use]`
`771`	`771`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`772`		`- self + ((rhs - self) * s)`
	`772`	`+ self * (1.0 - s) + rhs * s`
`773`	`773`	`}`
`774`	`774`
`775`	`775`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -827,7 +827,7 @@ impl Vec4 {`
`827`	`827`	`#[inline]`
`828`	`828`	`#[must_use]`
`829`	`829`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`830`		`- self + ((rhs - self) * s)`
	`830`	`+ self * (1.0 - s) + rhs * s`
`831`	`831`	`}`
`832`	`832`
`833`	`833`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -755,7 +755,7 @@ impl Vec4 {`
`755`	`755`	`#[inline]`
`756`	`756`	`#[must_use]`
`757`	`757`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`758`		`- self + ((rhs - self) * s)`
	`758`	`+ self * (1.0 - s) + rhs * s`
`759`	`759`	`}`
`760`	`760`
`761`	`761`	/// Moves towards `rhs` based on the value `d`.
Original file line number	Diff line number	Diff line change
`@@ -692,7 +692,7 @@ impl Vec2 {`
`692`	`692`	`#[inline]`
`693`	`693`	`#[must_use]`
`694`	`694`	`pub fn lerp(self, rhs: Self, s: f32) -> Self {`
`695`		`- self + ((rhs - self) * s)`
	`695`	`+ self * (1.0 - s) + rhs * s`
`696`	`696`	`}`
`697`	`697`
`698`	`698`	/// Moves towards `rhs` based on the value `d`.