invlerp and remap implementation

buildconfig/stubs/pygame/math.pyi

@@ -334,6 +334,8 @@ class Vector3(_GenericVector):
 
 
 def lerp(a: float, b: float, weight: float, do_clamp: bool = True, /) -> float: ...
+def invlerp(a: float, b: float, weight: float, /) -> float: ...
+def remap(i_min: float, i_max: float, o_min: float, o_max: float, value: float, /) -> float: ...
 def smoothstep(a: float, b: float, weight: float, /) -> float: ...
 
 

docs/reST/ref/math.rst

@@ -79,6 +79,37 @@ Multiple coordinates can be set using slices or swizzling
 
    .. ## math.lerp ##
 
+.. function:: invlerp
+
+   | :sl:`returns value inverse interpolated between a and b`
+   | :sg:`invlerp(a, b, value, /) -> float`
+
+   Returns a number which is an inverse interpolation between ``a``
+   and ``b``. The third parameter ``value`` is the result of the linear interpolation
+   between a and b with a certain coefficient. In other words, this coefficient
+   will be the result of this function.
+   If ``b - a`` is equal to 0, it raises a ``ZeroDivisionError``.
+
+   The formula is:
+
+   ``(v - a)/(b - a)``.
+
+   This is an example explaining what is above :
+
+   .. code-block:: python
+
+      > a = 10
+      > b = 20
+      > pygame.math.invlerp(10, 20, 11.5)
+      > 0.15
+      > pygame.math.lerp(10, 20, 0.15)
+      > 11.5
+
+
+   .. versionadded:: 2.5.0
+
+   .. ## math.invlerp ##
+
 .. function:: smoothstep
 
    | :sl:`returns value smoothly interpolated between a and b.`
@@ -102,6 +133,28 @@ Multiple coordinates can be set using slices or swizzling
 
    .. ## math.smoothstep ##
 
+.. function:: remap
+
+   | :sl:`remaps value from i_range to o_range`
+   | :sg:`remap(i_min, i_max, o_min, o_max, value, /) -> float`
+
+   Returns a number which is the value remapped from ``i_range`` to
+   ``o_range``.
+   If ``i_max - i_min`` is equal to 0, it raises a ``ZeroDivisionError``.
+
+   Example:
+
+   .. code-block:: python
+
+      > value = 50
+      > pygame.math.remap(0, 100, 0, 200, value)
+      > 100.0
+
+
+   .. versionadded:: 2.5.0
+
+   .. ## math.remap ##
+
 .. class:: Vector2
 
    | :sl:`a 2-Dimensional Vector`

src_c/doc/math_doc.h

@@ -2,7 +2,9 @@
 #define DOC_MATH "pygame module for vector classes"
 #define DOC_MATH_CLAMP "clamp(value, min, max, /) -> float\nreturns value clamped to min and max."
 #define DOC_MATH_LERP "lerp(a, b, value, do_clamp=True, /) -> float\nreturns value linearly interpolated between a and b"
+#define DOC_MATH_INVLERP "invlerp(a, b, value, /) -> float\nreturns value inverse interpolated between a and b"
 #define DOC_MATH_SMOOTHSTEP "smoothstep(a, b, value, /) -> float\nreturns value smoothly interpolated between a and b."
+#define DOC_MATH_REMAP "remap(i_min, i_max, o_min, o_max, value, /) -> float\nremaps value from i_range to o_range"
 #define DOC_MATH_VECTOR2 "Vector2() -> Vector2(0, 0)\nVector2(int) -> Vector2\nVector2(float) -> Vector2\nVector2(Vector2) -> Vector2\nVector2(x, y) -> Vector2\nVector2((x, y)) -> Vector2\na 2-Dimensional Vector"
 #define DOC_MATH_VECTOR2_DOT "dot(Vector2, /) -> float\ncalculates the dot- or scalar-product with the other vector"
 #define DOC_MATH_VECTOR2_CROSS "cross(Vector2, /) -> float\ncalculates the cross- or vector-product"

src_c/math.c

@@ -4192,6 +4192,18 @@ vector_elementwise(pgVector *vec, PyObject *_null)
     return (PyObject *)proxy;
 }
 
+inline double
+lerp(double a, double b, double v)
+{
+    return a + (b - a) * v;
+}
+
+inline double
+invlerp(double a, double b, double v)
+{
+    return (v - a) / (b - a);
+}
+
 static PyObject *
 math_clamp(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
 {
@@ -4233,6 +4245,72 @@ math_clamp(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
     return value;
 }
 
+#define RAISE_ARG_TYPE_ERROR(var)                                     \
+    if (PyErr_Occurred()) {                                           \
+        return RAISE(PyExc_TypeError,                                 \
+                     "The argument '" var "' must be a real number"); \
+    }
+
+static PyObject *
+math_invlerp(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
+{
+    if (nargs != 3)
+        return RAISE(PyExc_TypeError,
+                     "invlerp requires exactly 3 numeric arguments");
+
+    double a = PyFloat_AsDouble(args[0]);
+    RAISE_ARG_TYPE_ERROR("a")
+    double b = PyFloat_AsDouble(args[1]);
+    RAISE_ARG_TYPE_ERROR("b")
+    double t = PyFloat_AsDouble(args[2]);
+    RAISE_ARG_TYPE_ERROR("value")
+
+    if (PyErr_Occurred())
+        return RAISE(PyExc_ValueError,
+                     "invalid argument values passed to invlerp, numbers "
+                     "might be too small or too big");
+
+    if (b - a == 0)
+        return RAISE(PyExc_ValueError,
+                     "the result of b - a needs to be different from zero");
+
+    return PyFloat_FromDouble(invlerp(a, b, t));
+}
+
+#
+
+static PyObject *
+math_remap(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
+{
+    if (nargs != 5)
+        return RAISE(PyExc_TypeError,
+                     "remap requires exactly 5 numeric arguments");
+
+    PyObject *i_min = args[0];
+    PyObject *i_max = args[1];
+    PyObject *o_min = args[2];
+    PyObject *o_max = args[3];
+    PyObject *value = args[4];
+
+    double v = PyFloat_AsDouble(value);
+    RAISE_ARG_TYPE_ERROR("value")
+    double a = PyFloat_AsDouble(i_min);
+    RAISE_ARG_TYPE_ERROR("i_min")
+    double b = PyFloat_AsDouble(i_max);
+    RAISE_ARG_TYPE_ERROR("i_max")
+    double c = PyFloat_AsDouble(o_min);
+    RAISE_ARG_TYPE_ERROR("o_min")
+    double d = PyFloat_AsDouble(o_max);
+    RAISE_ARG_TYPE_ERROR("o_max")
+
+    if (b - a == 0)
+        return RAISE(
+            PyExc_ValueError,
+            "the result of i_max - i_min needs to be different from zero");
+
+    return PyFloat_FromDouble(lerp(c, d, invlerp(a, b, v)));
+}
+
 static PyObject *
 math_lerp(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
 {
@@ -4343,6 +4421,8 @@ math_disable_swizzling(pgVector *self, PyObject *_null)
 static PyMethodDef _math_methods[] = {
     {"clamp", (PyCFunction)math_clamp, METH_FASTCALL, DOC_MATH_CLAMP},
     {"lerp", (PyCFunction)math_lerp, METH_FASTCALL, DOC_MATH_LERP},
+    {"invlerp", (PyCFunction)math_invlerp, METH_FASTCALL, DOC_MATH_INVLERP},
+    {"remap", (PyCFunction)math_remap, METH_FASTCALL, DOC_MATH_REMAP},
     {"smoothstep", (PyCFunction)math_smoothstep, METH_FASTCALL,
      DOC_MATH_SMOOTHSTEP},
     {"enable_swizzling", (PyCFunction)math_enable_swizzling, METH_NOARGS,

test/math_test.py

@@ -86,6 +86,107 @@ def test_lerp(self):
             b = 2
             pygame.math.lerp(a, b, Vector2(0, 0))
 
+    def test_invlerp(self):
+        a = 0.0
+        b = 10.0
+        self.assertEqual(pygame.math.invlerp(a, b, 5.0), 0.5)
+
+        a = 0.0
+        b = 10.0
+        self.assertEqual(pygame.math.invlerp(a, b, 0.1), 0.01)
+
+        a = -10.0
+        b = 10.0
+        self.assertEqual(pygame.math.invlerp(a, b, 0.5), 0.525)
+
+        a = -10.0
+        b = 10.0
+        self.assertEqual(pygame.math.invlerp(a, b, 1.5), 0.575)
+
+        a = 0.0
+        b = 100.0
+        self.assertEqual(pygame.math.invlerp(a, b, 0.25), 0.0025)
+
+        with self.assertRaises(TypeError):
+            a = Vector2(0, 0)
+            b = Vector2(10.0, 10.0)
+            pygame.math.invlerp(a, b, 0.5)
+
+        with self.assertRaises(TypeError):
+            a = 1
+            b = 2
+            pygame.math.invlerp(a, b, Vector2(0, 0))
+
+        with self.assertRaises(ValueError):
+            a = 5
+            b = 5
+            pygame.math.invlerp(a, b, 5)
+
+        with self.assertRaises(TypeError):
+            a = 12**300
+            b = 11**30
+            pygame.math.invlerp(a, b, 1)
+
+    def test_remap(self):
+        a = 0.0
+        b = 10.0
+        c = 0.0
+        d = 100.0
+        self.assertEqual(pygame.math.remap(a, b, c, d, 1.0), 10.0)
+
+        a = 0.0
+        b = 10.0
+        c = 0.0
+        d = 100.0
+        self.assertEqual(pygame.math.remap(a, b, c, d, -1.0), -10.0)
+
+        a = -10.0
+        b = 10.0
+        c = -20.0
+        d = 20.0
+        self.assertEqual(pygame.math.remap(a, b, c, d, 0.0), 0.0)
+
+        a = -10.0
+        b = 10.0
+        c = 10.0
+        d = 110.0
+        self.assertEqual(pygame.math.remap(a, b, c, d, -8.0), 20.0)
+
+        with self.assertRaises(TypeError):
+            a = Vector2(0, 0)
+            b = "fish"
+            c = "durk"
+            d = Vector2(100, 100)
+            pygame.math.remap(a, b, c, d, 10)
+
+        with self.assertRaises(TypeError):
+            a = 1
+            b = 2
+            c = 10
+            d = 20
+            pygame.math.remap(a, b, c, d, Vector2(0, 0))
+
+        with self.assertRaises(ValueError):
+            a = 5
+            b = 5
+            c = 0
+            d = 100
+            pygame.math.remap(a, b, c, d, 10)
+
+        with self.assertRaises(TypeError):
+            a = 12**300
+            b = 11**30
+            c = 20
+            d = 30
+            pygame.math.remap(a, b, c, d, 100 * 50)
+
+        with self.assertRaises(TypeError):
+            a = 12j
+            b = 11j
+            c = 10j
+            d = 9j
+            pygame.math.remap(a, b, c, d, 50j)
+
     def test_smoothstep(self):
         a = 0.0
         b = 10.0