Index: source/blender/src/view.c
===================================================================
--- source/blender/src/view.c	(revision 15735)
+++ source/blender/src/view.c	(working copy)
@@ -94,7 +94,10 @@
 #define TRACKBALLSIZE  (1.1)
 #define BL_NEAR_CLIP 0.001
 
+#define COS45 0.70710678118654746
+#define SIN45 COS45
 
+
 /* local prototypes ----------*/
 void setcameratoview3d(void); /* windows.c & toets.c */
 
@@ -793,6 +796,32 @@
 	BIF_view3d_previewrender_signal(curarea, PR_DBASE|PR_DISPRECT);
 }
 
+static int snap_view(float viewmat[][3], float *snapquat, float thres, int view, int oposite_dir){
+	float snapmat[3][3];
+	
+	QuatToMat3(snapquat, snapmat);
+	
+	if ((Inpf(snapmat[0], viewmat[0]) > thres) &&
+		(Inpf(snapmat[1], viewmat[1]) > thres) &&
+		(Inpf(snapmat[2], viewmat[2]) > thres)){
+		
+		QUATCOPY(G.vd->viewquat, snapquat);
+		
+		if (view){
+			G.vd->view = view;
+			if (oposite_dir){
+				G.vd->flag2 |= V3D_OPP_DIRECTION_NAME;
+			}else{
+				G.vd->flag2 &= ~V3D_OPP_DIRECTION_NAME;
+			}
+		}
+		
+		return 1;
+	}
+	
+	return 0;
+}
+
 void viewmove(int mode)
 {
 	static float lastofs[3] = {0,0,0};
@@ -951,7 +980,6 @@
 					/* New turntable view code by John Aughey */
 
 					float m[3][3];
-					float m_inv[3][3];
 					float xvec[3] = {1,0,0};
 					/* Sensitivity will control how fast the viewport rotates.  0.0035 was
 					   obtained experimentally by looking at viewport rotation sensitivities
@@ -961,11 +989,10 @@
 
 					/* Get the 3x3 matrix and its inverse from the quaternion */
 					QuatToMat3(G.vd->viewquat, m);
-					Mat3Inv(m_inv,m);
 
 					/* Determine the direction of the x vector (for rotating up and down) */
 					/* This can likely be compuated directly from the quaternion. */
-					Mat3MulVecfl(m_inv,xvec);
+					Mat3TransMulVecfl(m, xvec);
 
 					/* Perform the up/down rotation */
 					phi = sensitivity * -(mval[1] - mvalo[1]);
@@ -997,6 +1024,73 @@
 						VecAddf(G.vd->ofs, G.vd->ofs, obofs);
 					}
 				}
+				
+				/* check for view snap */
+				if (G.qual==LR_CTRLKEY){
+					int i;
+					int snapped;
+					float m[3][3];
+
+					static const float thres = 0.93; //cos(20 deg);
+					
+					static float mainviewquats [6][6] = {
+						/*{q0, q1, q3, q4, view, oposite_direction}*/
+						{COS45, -SIN45, 0.0, 0.0, 1, 0},  //front
+						{0.0, 0.0, -SIN45, -SIN45, 1, 1}, //back
+						{1.0, 0.0, 0.0, 0.0, 7, 0},       //top
+						{0.0, -1.0, 0.0, 0.0, 7, 1},      //bottom
+						{0.5, -0.5, -0.5, -0.5, 3, 0},    //left
+						{0.5, -0.5, 0.5, 0.5, 3, 1}       //right
+					};
+
+					QuatToMat3(G.vd->viewquat, m);
+
+					/* main named views snaps */
+					for (i = 0 ; i < 6; i++){
+						snapped = snap_view(m, mainviewquats[i], thres, (int)mainviewquats[i][4], (int)mainviewquats[i][5]);
+					}
+					
+					if (!snapped){
+						/* some 45 deg snaps */
+						double deg22_5 = M_PI / 8.0;
+						float cos22_5 = (float)cos(deg22_5);
+						float sin22_5 = (float)sin(deg22_5);
+						
+						float qTop[4];
+						float qTop45[4];
+						float qMid[4];
+						float qBot45[4];
+						float qBot[4];
+
+						float rotZ45[4] = {cos22_5, 0.0, 0.0, sin22_5};
+						float rotX45up[4] = {cos22_5, -sin22_5, 0.0, 0.0};
+						float rotX45down[4] = {cos22_5, sin22_5, 0.0, 0.0};
+						
+						QUATCOPY(qTop, mainviewquats[2]);
+						QUATCOPY(qMid, mainviewquats[0]);
+						QUATCOPY(qBot, mainviewquats[3]);
+						QuatMul(qTop45, mainviewquats[0], rotX45up);
+						QuatMul(qBot45, mainviewquats[0], rotX45down);
+						for (i = 0; i < 8; i++){
+							QuatMul(qMid, qMid, rotZ45);
+							if (snap_view(m, qMid, thres, 0, 0)) break;
+							
+							QuatMul(qTop, qTop, rotZ45);
+							if (snap_view(m, qTop, thres, 0, 0)) break;
+							
+							QuatMul(qBot, qBot, rotZ45);
+							if (snap_view(m, qBot, thres, 0, 0)) break;
+							
+							QuatMul(qTop45, qTop45, rotZ45);
+							if (snap_view(m, qTop45, thres, 0, 0)) break;
+	
+							QuatMul(qBot45, qBot45, rotZ45);
+							if (snap_view(m, qBot45, thres, 0, 0)) break;
+						}
+					}
+					
+				}
+				
 			}
 			else if(mode==1) {	/* translate */
 				if(G.vd->persp==V3D_CAMOB) {