d3dx8: Implement the spherical interpolation part for D3DXQuaternionSlerp.

dlls/d3dx8/math.c

@@ -1173,15 +1173,27 @@ D3DXQUATERNION* WINAPI D3DXQuaternionRotationYawPitchRoll(D3DXQUATERNION *pout,
 
 D3DXQUATERNION* WINAPI D3DXQuaternionSlerp(D3DXQUATERNION *pout, CONST D3DXQUATERNION *pq1, CONST D3DXQUATERNION *pq2, FLOAT t)
 {
-    FLOAT dot, epsilon;
+    FLOAT dot, epsilon, temp, theta, u;
 
     epsilon = 1.0f;
+    temp = 1.0f - t;
+    u = t;
     dot = D3DXQuaternionDot(pq1, pq2);
-    if ( dot < 0.0f) epsilon = -1.0f;
-    pout->x = (1.0f - t) * pq1->x + epsilon * t * pq2->x;
-    pout->y = (1.0f - t) * pq1->y + epsilon * t * pq2->y;
-    pout->z = (1.0f - t) * pq1->z + epsilon * t * pq2->z;
-    pout->w = (1.0f - t) * pq1->w + epsilon * t * pq2->w;
+    if ( dot < 0.0f )
+    {
+        epsilon = -1.0f;
+        dot = -dot;
+    }
+    if( 1.0f - dot > 0.001f )
+    {
+        theta = acos(dot);
+        temp  = sin(theta * temp) / sin(theta);
+        u = sin(theta * u) / sin(theta);
+    }
+    pout->x = temp * pq1->x + epsilon * u * pq2->x;
+    pout->y = temp * pq1->y + epsilon * u * pq2->y;
+    pout->z = temp * pq1->z + epsilon * u * pq2->z;
+    pout->w = temp * pq1->w + epsilon * u * pq2->w;
     return pout;
 }
 

dlls/d3dx8/tests/math.c

@@ -582,7 +582,7 @@ static void D3DXPlaneTest(void)
 static void D3X8QuaternionTest(void)
 {
     D3DXMATRIX mat;
-    D3DXQUATERNION expectedquat, gotquat, Nq, Nq1, nul, q, r, s, t, u;
+    D3DXQUATERNION expectedquat, gotquat, Nq, Nq1, nul, smallq, smallr, q, r, s, t, u;
     LPD3DXQUATERNION funcpointer;
     D3DXVECTOR3 axis, expectedvec;
     FLOAT angle, expected, got, scale, scale2;
@@ -591,8 +591,10 @@ static void D3X8QuaternionTest(void)
     nul.x = 0.0f; nul.y = 0.0f; nul.z = 0.0f; nul.w = 0.0f;
     q.x = 1.0f, q.y = 2.0f; q.z = 4.0f; q.w = 10.0f;
     r.x = -3.0f; r.y = 4.0f; r.z = -5.0f; r.w = 7.0;
-    t.x = -1111.0f, t.y= 111.0f; t.z = -11.0f; t.w = 1.0f;
+    t.x = -1111.0f, t.y = 111.0f; t.z = -11.0f; t.w = 1.0f;
     u.x = 91.0f; u.y = - 82.0f; u.z = 7.3f; u.w = -6.4f;
+    smallq.x = 0.1f; smallq.y = 0.2f; smallq.z= 0.3f; smallq.w = 0.4f;
+    smallr.x = 0.5f; smallr.y = 0.6f; smallr.z= 0.7f; smallq.w = 0.8f;
 
     scale = 0.3f;
     scale2 = 0.78f;
@@ -873,6 +875,9 @@ static void D3X8QuaternionTest(void)
     expectedquat.x = 334.0f; expectedquat.y = -31.9f; expectedquat.z = 6.1f; expectedquat.w = 6.7f;
     D3DXQuaternionSlerp(&gotquat,&q,&t,scale);
     expect_vec4(expectedquat,gotquat);
+    expectedquat.x = 0.267071f; expectedquat.y = 0.384114f; expectedquat.z = 0.501157f; expectedquat.w = 0.636291f;
+    D3DXQuaternionSlerp(&gotquat,&smallq,&smallr,scale);
+    expect_vec4(expectedquat,gotquat);
 
 /*_______________D3DXQuaternionSquad________________________*/
     expectedquat.x = -156.296f; expectedquat.y = 30.242f; expectedquat.z = -2.5022f; expectedquat.w = 7.3576f;