Translate the source position separately

This is to handle the case where an app specifies the same values for the
source and listener, and expects centered panning. This fails due to floating-
point errors in the matrix, causing the result to be ever-so-slightly off of 0.

This error would normally be hidden by the position normalization, which will
not lengthen a distance shorter than the reference distance so the panning
would be nearly imperceptible. But that also fails if the reference distance
is set to 0, causing the position to expand to a full unit.

Keep the 4x4 matrix calculations, however. It will still be useful for the
requested listener matrix extension.

1 files changed, 7 insertions, 11 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index 2deb993d..2bc5cde2 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -580,7 +580,7 @@ static ALvoid CalcSourceParams(const ALCcontext *ALContext, ALsource *ALSource)
     //1. Translate Listener to origin (convert to head relative)
     if(ALSource->bHeadRelative==AL_FALSE)
     {
-        ALfloat U[3],V[3],N[3],P[3];
+        ALfloat U[3],V[3],N[3];
 
         // Build transform matrix
         memcpy(N, ALContext->Listener.Forward, sizeof(N));  // At-vector
@@ -589,19 +589,15 @@ static ALvoid CalcSourceParams(const ALCcontext *ALContext, ALsource *ALSource)
         aluNormalize(V);  // Normalized Up-vector
         aluCrossproduct(N, V, U); // Right-vector
         aluNormalize(U);  // Normalized Right-vector
-        P[0] = -(ALContext->Listener.Position[0]*U[0] + // Translation
-                 ALContext->Listener.Position[1]*U[1] +
-                 ALContext->Listener.Position[2]*U[2]);
-        P[1] = -(ALContext->Listener.Position[0]*V[0] +
-                 ALContext->Listener.Position[1]*V[1] +
-                 ALContext->Listener.Position[2]*V[2]);
-        P[2] = -(ALContext->Listener.Position[0]*-N[0] +
-                 ALContext->Listener.Position[1]*-N[1] +
-                 ALContext->Listener.Position[2]*-N[2]);
         Matrix[0][0] = U[0]; Matrix[0][1] = V[0]; Matrix[0][2] = -N[0]; Matrix[0][3] = 0.0f;
         Matrix[1][0] = U[1]; Matrix[1][1] = V[1]; Matrix[1][2] = -N[1]; Matrix[1][3] = 0.0f;
         Matrix[2][0] = U[2]; Matrix[2][1] = V[2]; Matrix[2][2] = -N[2]; Matrix[2][3] = 0.0f;
-        Matrix[3][0] = P[0]; Matrix[3][1] = P[1]; Matrix[3][2] =  P[2]; Matrix[3][3] = 1.0f;
+        Matrix[3][0] = 0.0f; Matrix[3][1] = 0.0f; Matrix[3][2] =  0.0f; Matrix[3][3] = 1.0f;
+
+        // Translate position
+        Position[0] -= ALContext->Listener.Position[0];
+        Position[1] -= ALContext->Listener.Position[1];
+        Position[2] -= ALContext->Listener.Position[2];
 
         // Transform source position and direction into listener space
         aluMatrixVector(Position, 1.0f, Matrix);