From 7f9bfee0ac4707f2586bd25c04c3883c9eb1be9e Mon Sep 17 00:00:00 2001 From: Meriipu Date: Sat, 25 Jul 2020 16:11:23 +0200 Subject: [PATCH] GDScript: Clarified/fixed inaccuracies in the built-in function docs. The input to smoothstep is not actually a weight, and the decscription of smoothstep was pretty hard to understand and easy to misinterpret. Clarified what it means to be approximately equal. nearest_po2 does not do what the descriptions says it does. For one, it returns the same power if the input is a power of 2. Second, it returns 0 if the input is negative or 0, while the smallest possible integral power of 2 actually is 1 (2^0 = 1). Due to the implementation and how it is used in a lot of places, it does not seem wise to change such a core function however, and I decided it is better to alter the description of the built-in. Added a few examples/clarifications/edge-cases. --- core/math/math_funcs.h | 12 +++++------ modules/gdscript/doc_classes/@GDScript.xml | 25 ++++++++++++++++------ modules/gdscript/gdscript_functions.cpp | 2 +- 3 files changed, 26 insertions(+), 13 deletions(-) diff --git a/core/math/math_funcs.h b/core/math/math_funcs.h index 7a9fd60e23f1..9f8d4da5b34d 100644 --- a/core/math/math_funcs.h +++ b/core/math/math_funcs.h @@ -231,19 +231,19 @@ public: static _ALWAYS_INLINE_ double range_lerp(double p_value, double p_istart, double p_istop, double p_ostart, double p_ostop) { return Math::lerp(p_ostart, p_ostop, Math::inverse_lerp(p_istart, p_istop, p_value)); } static _ALWAYS_INLINE_ float range_lerp(float p_value, float p_istart, float p_istop, float p_ostart, float p_ostop) { return Math::lerp(p_ostart, p_ostop, Math::inverse_lerp(p_istart, p_istop, p_value)); } - static _ALWAYS_INLINE_ double smoothstep(double p_from, double p_to, double p_weight) { + static _ALWAYS_INLINE_ double smoothstep(double p_from, double p_to, double p_s) { if (is_equal_approx(p_from, p_to)) { return p_from; } - double x = CLAMP((p_weight - p_from) / (p_to - p_from), 0.0, 1.0); - return x * x * (3.0 - 2.0 * x); + double s = CLAMP((p_s - p_from) / (p_to - p_from), 0.0, 1.0); + return s * s * (3.0 - 2.0 * s); } - static _ALWAYS_INLINE_ float smoothstep(float p_from, float p_to, float p_weight) { + static _ALWAYS_INLINE_ float smoothstep(float p_from, float p_to, float p_s) { if (is_equal_approx(p_from, p_to)) { return p_from; } - float x = CLAMP((p_weight - p_from) / (p_to - p_from), 0.0f, 1.0f); - return x * x * (3.0f - 2.0f * x); + float s = CLAMP((p_s - p_from) / (p_to - p_from), 0.0f, 1.0f); + return s * s * (3.0f - 2.0f * s); } static _ALWAYS_INLINE_ double move_toward(double p_from, double p_to, double p_delta) { return abs(p_to - p_from) <= p_delta ? p_to : p_from + SGN(p_to - p_from) * p_delta; } static _ALWAYS_INLINE_ float move_toward(float p_from, float p_to, float p_delta) { return abs(p_to - p_from) <= p_delta ? p_to : p_from + SGN(p_to - p_from) * p_delta; } diff --git a/modules/gdscript/doc_classes/@GDScript.xml b/modules/gdscript/doc_classes/@GDScript.xml index 36de66ea524c..d8825ecc9af3 100644 --- a/modules/gdscript/doc_classes/@GDScript.xml +++ b/modules/gdscript/doc_classes/@GDScript.xml @@ -318,7 +318,7 @@ The natural exponential function. It raises the mathematical constant [b]e[/b] to the power of [code]s[/code] and returns it. - [b]e[/b] has an approximate value of 2.71828. + [b]e[/b] has an approximate value of 2.71828, and can be obtained with [code]exp(1)[/code]. For exponents to other bases use the method [method pow]. [codeblock] a = exp(2) # Approximately 7.39 @@ -505,6 +505,8 @@ Returns [code]true[/code] if [code]a[/code] and [code]b[/code] are approximately equal to each other. + Here, approximately equal means that [code]a[/code] and [code]b[/code] are within a small internal epsilon of each other, which scales with the magnitude of the numbers. + Infinity values of the same sign are considered equal. @@ -641,6 +643,7 @@ [codeblock] log(10) # Returns 2.302585 [/codeblock] + [b]Note:[/b] The logarithm of [code]0[/code] returns [code]-inf[/code], while negative values return [code]-nan[/code]. @@ -686,7 +689,9 @@ Moves [code]from[/code] toward [code]to[/code] by the [code]delta[/code] value. Use a negative [code]delta[/code] value to move away. [codeblock] + move_toward(5, 10, 4) # Returns 9 move_toward(10, 5, 4) # Returns 6 + move_toward(10, 5, -1.5) # Returns 11.5 [/codeblock] @@ -696,12 +701,17 @@ - Returns the nearest larger power of 2 for integer [code]value[/code]. + Returns the nearest equal or larger power of 2 for integer [code]value[/code]. + In other words, returns the smallest value [code]a[/code] where [code]a = pow(2, n)[/code] such that [code]value <= a[/code] for some non-negative integer [code]n[/code]. [codeblock] nearest_po2(3) # Returns 4 nearest_po2(4) # Returns 4 nearest_po2(5) # Returns 8 + + nearest_po2(0) # Returns 0 (this may not be what you expect) + nearest_po2(-1) # Returns 0 (this may not be what you expect) [/codeblock] + [b]WARNING:[/b] Due to the way it is implemented, this function returns [code]0[/code] rather than [code]1[/code] for non-positive values of [code]value[/code] (in reality, 1 is the smallest integer power of 2). @@ -1093,12 +1103,15 @@ - + - Returns a number smoothly interpolated between the [code]from[/code] and [code]to[/code], based on the [code]weight[/code]. Similar to [method lerp], but interpolates faster at the beginning and slower at the end. + Returns the result of smoothly interpolating the value of [code]s[/code] between [code]0[/code] and [code]1[/code], based on the where [code]s[/code] lies with respect to the edges [code]from[/code] and [code]to[/code]. + The return value is [code]0[/code] if [code]s <= from[/code], and [code]1[/code] if [code]s >= to[/code]. If [code]s[/code] lies between [code]from[/code] and [code]to[/code], the returned value follows an S-shaped curve that maps [code]s[/code] between [code]0[/code] and [code]1[/code]. + This S-shaped curve is the cubic Hermite interpolator, given by [code]f(s) = 3*s^2 - 2*s^3[/code]. [codeblock] - smoothstep(0, 2, 0.5) # Returns 0.15 + smoothstep(0, 2, -5.0) # Returns 0.0 + smoothstep(0, 2, 0.5) # Returns 0.15625 smoothstep(0, 2, 1.0) # Returns 0.5 smoothstep(0, 2, 2.0) # Returns 1.0 [/codeblock] @@ -1114,7 +1127,7 @@ [codeblock] sqrt(9) # Returns 3 [/codeblock] - If you need negative inputs, use [code]System.Numerics.Complex[/code] in C#. + [b]Note:[/b]Negative values of [code]s[/code] return NaN. If you need negative inputs, use [code]System.Numerics.Complex[/code] in C#. diff --git a/modules/gdscript/gdscript_functions.cpp b/modules/gdscript/gdscript_functions.cpp index 7f2a62a8e976..fefbf906f03e 100644 --- a/modules/gdscript/gdscript_functions.cpp +++ b/modules/gdscript/gdscript_functions.cpp @@ -1636,7 +1636,7 @@ MethodInfo GDScriptFunctions::get_info(Function p_func) { return mi; } break; case MATH_SMOOTHSTEP: { - MethodInfo mi("smoothstep", PropertyInfo(Variant::FLOAT, "from"), PropertyInfo(Variant::FLOAT, "to"), PropertyInfo(Variant::FLOAT, "weight")); + MethodInfo mi("smoothstep", PropertyInfo(Variant::FLOAT, "from"), PropertyInfo(Variant::FLOAT, "to"), PropertyInfo(Variant::FLOAT, "s")); mi.return_val.type = Variant::FLOAT; return mi; } break;