From 29583345a087824e5b09510d1c7330090b78a111 Mon Sep 17 00:00:00 2001
From: danij <danij@dengine.net>
Date: Mon, 2 Dec 2013 20:30:19 +0000
Subject: [PATCH] libdeng2: Added template de::lerp()

---
 doomsday/client/src/render/rend_model.cpp | 28 ++++++++---------------
 doomsday/libdeng2/include/de/math.h       | 13 +++++++++++
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/doomsday/client/src/render/rend_model.cpp b/doomsday/client/src/render/rend_model.cpp
index e0be0f8c97..f08bac358a 100644
--- a/doomsday/client/src/render/rend_model.cpp
+++ b/doomsday/client/src/render/rend_model.cpp
@@ -498,14 +498,6 @@ static void Mod_RenderPrimitives(rendcmd_t mode, Model::Primitives const &primit
     }
 }
 
-/**
- * Linear interpolation between two values.
- */
-static inline float Mod_Lerp(float start, float end, float pos)
-{
-    return end * pos + start * (1 - pos);
-}
-
 /**
  * Interpolate linearly between two sets of vertices.
  */
@@ -513,7 +505,7 @@ static void Mod_LerpVertices(float inter, int count, ModelFrame const &from,
     ModelFrame const &to, Vector3f *posOut, Vector3f *normOut)
 {
     DENG2_ASSERT(&from.model == &to.model); // sanity check.
-    DENG2_ASSERT(&activeLod->model == &from.model); // sanity check.
+    DENG2_ASSERT(!activeLod || &activeLod->model == &from.model); // sanity check.
     DENG2_ASSERT(from.vertices.count() == to.vertices.count()); // sanity check.
 
     ModelFrame::VertexBuf::const_iterator startIt = from.vertices.begin();
@@ -532,14 +524,12 @@ static void Mod_LerpVertices(float inter, int count, ModelFrame const &from,
     }
     else
     {
-        float const invInter = 1 - inter;
-
         for(int i = 0; i < count; ++i, startIt++, endIt++, posOut++, normOut++)
         {
             if(!activeLod || activeLod->hasVertex(i))
             {
-                *posOut  = startIt->pos  * invInter + endIt->pos  * inter;
-                *normOut = startIt->norm * invInter + endIt->norm * inter;
+                *posOut  = de::lerp(startIt->pos,  endIt->pos,  inter);
+                *normOut = de::lerp(startIt->norm, endIt->norm, inter);
             }
         }
     }
@@ -876,11 +866,11 @@ static void Mod_RenderSubModel(uint number, rendmodelparams_t const *parm)
 
     // Model space => World space
     glTranslatef(parm->origin[VX] + parm->srvo[VX] +
-                   Mod_Lerp(mf->offset.x, mfNext->offset.x, inter),
+                   de::lerp(mf->offset.x, mfNext->offset.x, inter),
                  parm->origin[VZ] + parm->srvo[VZ] +
-                   Mod_Lerp(mf->offset.y, mfNext->offset.y, inter),
+                   de::lerp(mf->offset.y, mfNext->offset.y, inter),
                  parm->origin[VY] + parm->srvo[VY] + zSign *
-                   Mod_Lerp(mf->offset.z, mfNext->offset.z, inter));
+                   de::lerp(mf->offset.z, mfNext->offset.z, inter));
 
     if(parm->extraYawAngle || parm->extraPitchAngle)
     {
@@ -898,9 +888,9 @@ static void Mod_RenderSubModel(uint number, rendmodelparams_t const *parm)
               0, 0, 1);
 
     // Scaling and model space offset.
-    glScalef(Mod_Lerp(mf->scale.x, mfNext->scale.x, inter),
-             Mod_Lerp(mf->scale.y, mfNext->scale.y, inter),
-             Mod_Lerp(mf->scale.z, mfNext->scale.z, inter));
+    glScalef(de::lerp(mf->scale.x, mfNext->scale.x, inter),
+             de::lerp(mf->scale.y, mfNext->scale.y, inter),
+             de::lerp(mf->scale.z, mfNext->scale.z, inter));
     if(parm->extraScale)
     {
         // Particle models have an extra scale.
diff --git a/doomsday/libdeng2/include/de/math.h b/doomsday/libdeng2/include/de/math.h
index 73c655e046..72997d173e 100644
--- a/doomsday/libdeng2/include/de/math.h
+++ b/doomsday/libdeng2/include/de/math.h
@@ -152,6 +152,19 @@ inline dint cmp(Type const &a, Type const &b) {
     return 0;
 }
 
+/**
+ * Linear interpolation between two values.
+ *
+ * @param start  Value to interpolate from.
+ * @param end    Value to interpolate to.
+ * @param pos    Normalized interpolation point [0..1].
+ */
+template <typename Type>
+static Type lerp(Type start, Type end, float pos)
+{
+    return end * pos + start * (1 - pos);
+}
+
 } // namespace de
 
 #endif /* LIBDENG2_MATH_H */