Handle the listener position separate from the rotation matrix

It's too unstable with larger vectors. Even when the source and listener
positions are the same, floating point precision can cause noticeable rounding
errors.

2 files changed, 10 insertions, 12 deletions

diff --git a/alc/alu.cpp b/alc/alu.cpp
index d370aba7..00b91bd4 100644
--- a/alc/alu.cpp
+++ b/alc/alu.cpp
@@ -386,6 +386,9 @@ bool CalcListenerParams(ContextBase *ctx)
         std::memory_order_acq_rel)};
     if(!props) return false;
 
+    const alu::Vector pos{props->Position[0], props->Position[1], props->Position[2], 1.0f};
+    ctx->mParams.Position = pos;
+
     /* AT then UP */
     alu::Vector N{props->OrientAt[0], props->OrientAt[1], props->OrientAt[2], 0.0f};
     N.normalize();
@@ -395,21 +398,15 @@ bool CalcListenerParams(ContextBase *ctx)
     alu::Vector U{N.cross_product(V)};
     U.normalize();
 
-    const alu::MatrixR<double> rot{
+    const alu::Matrix rot{
         U[0], V[0], -N[0], 0.0,
         U[1], V[1], -N[1], 0.0,
         U[2], V[2], -N[2], 0.0,
          0.0,  0.0,   0.0, 1.0};
-    const alu::VectorR<double> pos{props->Position[0],props->Position[1],props->Position[2],1.0};
-    const alu::VectorR<double> vel{props->Velocity[0],props->Velocity[1],props->Velocity[2],0.0};
-    const alu::Vector P{alu::cast_to<float>(rot * pos)};
+    const alu::Vector vel{props->Velocity[0], props->Velocity[1], props->Velocity[2], 0.0};
 
-    ctx->mParams.Matrix = alu::Matrix{
-         U[0],  V[0], -N[0], 0.0f,
-         U[1],  V[1], -N[1], 0.0f,
-         U[2],  V[2], -N[2], 0.0f,
-        -P[0], -P[1], -P[2], 1.0f};
-    ctx->mParams.Velocity = alu::cast_to<float>(rot * vel);
+    ctx->mParams.Matrix = rot;
+    ctx->mParams.Velocity = rot * vel;
 
     ctx->mParams.Gain = props->Gain * ctx->mGainBoost;
     ctx->mParams.MetersPerUnit = props->MetersPerUnit;
@@ -1318,7 +1315,7 @@ void CalcAttnSourceParams(Voice *voice, const VoiceProps *props, const ContextBa
     if(!props->HeadRelative)
     {
         /* Transform source vectors */
-        Position = context->mParams.Matrix * Position;
+        Position = context->mParams.Matrix * (Position - context->mParams.Position);
         Velocity = context->mParams.Matrix * Velocity;
         Direction = context->mParams.Matrix * Direction;
     }
@@ -1330,7 +1327,7 @@ void CalcAttnSourceParams(Voice *voice, const VoiceProps *props, const ContextBa
 
     const bool directional{Direction.normalize() > 0.0f};
     alu::Vector ToSource{Position[0], Position[1], Position[2], 0.0f};
-    const float Distance{ToSource.normalize(props->RefDistance / 1024.0f)};
+    const float Distance{ToSource.normalize()};
 
     /* Initial source gain */
     GainTriplet DryGain{props->Gain, 1.0f, 1.0f};
diff --git a/alc/context.cpp b/alc/context.cpp
index 9f0b6272..a97c2a68 100644
--- a/alc/context.cpp
+++ b/alc/context.cpp
@@ -289,6 +289,7 @@ void ALCcontext::init()
     mExtensionList = alExtList;
 
 
+    mParams.Position = alu::Vector{0.0f, 0.0f, 0.0f, 1.0f};
     mParams.Matrix = alu::Matrix::Identity();
     mParams.Velocity = alu::Vector{};
     mParams.Gain = mListener.Gain;