From d3833b6d618ff05f44c28eab67bc91ee5a3ba92d Mon Sep 17 00:00:00 2001
From: Ansariel Hiller <Ansariel@users.noreply.github.com>
Date: Fri, 27 Sep 2024 03:35:42 +0200
Subject: Fix lerp issues and eliminate flerp in favor of std::lerp (#2712)

---
 indra/llmath/llmath.h                      |  9 +--------
 indra/llmath/llvolume.cpp                  | 28 ++++++++++++++--------------
 indra/newview/llpanelprimmediacontrols.cpp |  2 +-
 3 files changed, 16 insertions(+), 23 deletions(-)

(limited to 'indra')

diff --git a/indra/llmath/llmath.h b/indra/llmath/llmath.h
index 1d6d986207..0348dad8fe 100644
--- a/indra/llmath/llmath.h
+++ b/indra/llmath/llmath.h
@@ -359,13 +359,6 @@ inline F32 snap_to_sig_figs(F32 foo, S32 sig_figs)
 }
 
 using std::lerp;
-// Even though there's now a std::lerp() function that appears to do the same
-// as this function, in some cases MSVC likes this one better: some calls to
-// std::lerp() produce fatal argument conversion warnings.
-inline F32 flerp(F32 a, F32 b, F32 u)
-{
-    return a + ((b - a) * u);
-}
 
 inline F32 lerp2d(F32 x00, F32 x01, F32 x10, F32 x11, F32 u, F32 v)
 {
@@ -490,7 +483,7 @@ inline U32 get_next_power_two(U32 val, U32 max_power_two)
 //get the gaussian value given the linear distance from axis x and guassian value o
 inline F32 llgaussian(F32 x, F32 o)
 {
-    return 1.f/(F_SQRT_TWO_PI*o)*powf(F_E, -(x*x)/(2*o*o));
+    return 1.f/(F_SQRT_TWO_PI*o)*powf(F_E, -(x*x)/(2.f*o*o));
 }
 
 //helper function for removing outliers
diff --git a/indra/llmath/llvolume.cpp b/indra/llmath/llvolume.cpp
index 275e5bcb43..00a56edf68 100644
--- a/indra/llmath/llvolume.cpp
+++ b/indra/llmath/llvolume.cpp
@@ -1294,9 +1294,9 @@ void LLPath::genNGon(const LLPathParams& params, S32 sides, F32 startOff, F32 en
     c       = cos(ang)*lerp(radius_start, radius_end, t);
 
 
-    pt->mPos.set(0 + flerp(0,params.getShear().mV[0],s)
-                      + flerp(-skew ,skew, t) * 0.5f,
-                    c + flerp(0,params.getShear().mV[1],s),
+    pt->mPos.set(0 + lerp(0.f,params.getShear().mV[0],s)
+                      + lerp(-skew ,skew, t) * 0.5f,
+                    c + lerp(0.f,params.getShear().mV[1],s),
                     s);
     pt->mScale.set(hole_x * lerp(taper_x_begin, taper_x_end, t),
         hole_y * lerp(taper_y_begin, taper_y_end, t),
@@ -1327,9 +1327,9 @@ void LLPath::genNGon(const LLPathParams& params, S32 sides, F32 startOff, F32 en
         c   = cos(ang)*lerp(radius_start, radius_end, t);
         s   = sin(ang)*lerp(radius_start, radius_end, t);
 
-        pt->mPos.set(0 + flerp(0,params.getShear().mV[0],s)
-                          + flerp(-skew ,skew, t) * 0.5f,
-                        c + flerp(0,params.getShear().mV[1],s),
+        pt->mPos.set(0 + lerp(0.f,params.getShear().mV[0],s)
+                          + lerp(-skew ,skew, t) * 0.5f,
+                        c + lerp(0.f,params.getShear().mV[1],s),
                         s);
 
         pt->mScale.set(hole_x * lerp(taper_x_begin, taper_x_end, t),
@@ -1354,9 +1354,9 @@ void LLPath::genNGon(const LLPathParams& params, S32 sides, F32 startOff, F32 en
     c   = cos(ang)*lerp(radius_start, radius_end, t);
     s   = sin(ang)*lerp(radius_start, radius_end, t);
 
-    pt->mPos.set(0 + flerp(0,params.getShear().mV[0],s)
-                      + flerp(-skew ,skew, t) * 0.5f,
-                    c + flerp(0,params.getShear().mV[1],s),
+    pt->mPos.set(0 + lerp(0.f,params.getShear().mV[0],s)
+                      + lerp(-skew ,skew, t) * 0.5f,
+                    c + lerp(0.f,params.getShear().mV[1],s),
                     s);
     pt->mScale.set(hole_x * lerp(taper_x_begin, taper_x_end, t),
                    hole_y * lerp(taper_y_begin, taper_y_end, t),
@@ -1494,8 +1494,8 @@ bool LLPath::generate(const LLPathParams& params, F32 detail, S32 split,
             for (S32 i=0;i<np;i++)
             {
                 F32 t = lerp(params.getBegin(),params.getEnd(),(F32)i * mStep);
-                mPath[i].mPos.set(flerp(0,params.getShear().mV[0],t),
-                                     flerp(0,params.getShear().mV[1],t),
+                mPath[i].mPos.set(lerp(0.f,params.getShear().mV[0],t),
+                                     lerp(0.f,params.getShear().mV[1],t),
                                      t - 0.5f);
                 LLQuaternion quat;
                 quat.setQuat(lerp(F_PI * params.getTwistBegin(),F_PI * params.getTwist(),t),0,0,1);
@@ -1559,10 +1559,10 @@ bool LLPath::generate(const LLPathParams& params, F32 detail, S32 split,
         {
             F32 t = (F32)i * mStep;
             mPath[i].mPos.set(0,
-                                flerp(0,   -sin(F_PI*params.getTwist()*t)*0.5f,t),
+                                lerp(0.f,  -sin(F_PI*params.getTwist()*t)*0.5f,t),
                                 lerp(-0.5f, cos(F_PI*params.getTwist()*t)*0.5f,t));
-            mPath[i].mScale.set(flerp(1,params.getScale().mV[0],t),
-                                flerp(1,params.getScale().mV[1],t), 0,1);
+            mPath[i].mScale.set(lerp(1.f,params.getScale().mV[0],t),
+                                lerp(1.f,params.getScale().mV[1],t), 0.f, 1.f);
             mPath[i].mTexT  = t;
             LLQuaternion quat;
             quat.setQuat(F_PI * params.getTwist() * t,1,0,0);
diff --git a/indra/newview/llpanelprimmediacontrols.cpp b/indra/newview/llpanelprimmediacontrols.cpp
index 1a092234fb..955b5e7730 100644
--- a/indra/newview/llpanelprimmediacontrols.cpp
+++ b/indra/newview/llpanelprimmediacontrols.cpp
@@ -777,7 +777,7 @@ void LLPanelPrimMediaControls::draw()
     else if(mFadeTimer.getStarted())
     {
         F32 time = mFadeTimer.getElapsedTimeF32();
-        alpha *= llmax(flerp(1.0, 0.0, time / mControlFadeTime), 0.0f);
+        alpha *= llmax(lerp(1.0f, 0.0f, time / mControlFadeTime), 0.0f);
 
         if(time >= mControlFadeTime)
         {
-- 
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