add Lerp function

geometry.go

@@ -106,6 +106,15 @@ func (u Vec) Map(f func(float64) float64) Vec {
 	)
 }
 
+// Lerp returns a linear interpolation between vectors a and b.
+//
+// This function basically returns a point along the line between a and b and t chooses which point.
+// If t is 0, then a will be returned, if t is 1, b will be returned. Anything between 0 and 1 will
+// return the appropriate point between a and b and so on.
+func Lerp(a, b Vec, t float64) Vec {
+	return a.Scaled(1-t) + b.Scaled(t)
+}
+
 // Rect is a 2D rectangle aligned with the axes of the coordinate system. It has a position
 // and a size.
 //

util.go

@@ -12,17 +12,6 @@ func clamp(x, low, high float64) float64 {
 	return x
 }
 
-func lerp(x float64, a, b Vec) Vec {
-	return a.Scaled(1-x) + b.Scaled(x)
-}
-
-func lerp2d(x, a, b Vec) Vec {
-	return V(
-		lerp(x.X(), a, b).X(),
-		lerp(x.Y(), a, b).Y(),
-	)
-}
-
 func transformToMat(t ...Transform) mgl32.Mat3 {
 	mat := mgl32.Ident3()
 	for i := range t {
@@ -30,11 +19,3 @@ func transformToMat(t ...Transform) mgl32.Mat3 {
 	}
 	return mat
 }
-
-func pictureBounds(p Picture, v Vec) Vec {
-	w, h := p.Bounds().Size.XY()
-	a := p.Bounds().Pos
-	b := p.Bounds().Pos + p.Bounds().Size
-	u := lerp2d(v, a, b)
-	return V(u.X()/w, u.Y()/h)
-}