Index: /issm/trunk/src/c/InterpFromMeshToGridx/InterpFromMeshToGridx.cpp
===================================================================
--- /issm/trunk/src/c/InterpFromMeshToGridx/InterpFromMeshToGridx.cpp	(revision 2303)
+++ /issm/trunk/src/c/InterpFromMeshToGridx/InterpFromMeshToGridx.cpp	(revision 2304)
@@ -18,6 +18,8 @@
 	/*Intermediary*/
 	int    i,j,n;
+	int    i1,i2,j1,j2;
 	int    interpolation_type;
 	bool   debug;
+	int    xflip,yflip;
 	double area;
 	double area_1,area_2,area_3;
@@ -57,5 +59,11 @@
 	debug=(bool)((double)ncols*nlines*nels >= pow((double)10,(double)10));
 
-	/*Initialize coordintes and griddata*/
+	/*figure out if x or y are flipped*/
+	if (xposting<0) xflip=1;
+	else xflip=0;
+	if (yposting<0) yflip=1;
+	else yflip=0;
+
+	/*Compute coordinates lists*/
 	// EAST = ACTUAL WEST !!!!!!!!!!!!!!!
 	cornersouth=cornernorth-nlines*yposting;
@@ -65,4 +73,6 @@
 	for(i=0;i<=nlines;i++)   y_m[i]   = cornersouth + yposting*i;
 	for(i=0;i<=ncols; i++)   x_m[i]   = cornereast  + xposting*i;
+
+	/*Initialize coordintes and griddata*/
 	for(i=0;i<nlines;i++){
 		for(j=0;j<ncols; j++){
@@ -72,19 +82,15 @@
 	
 	/*Get extreme coordinates of the grid*/
-	if (xposting>0){
-		x_grid_min=cornereast;
-		x_grid_max=cornerwest;
+	if (xflip){
+		x_grid_min=x_grid[ncols-1]; x_grid_max=x_grid[0];
 	}
 	else{
-		x_grid_min=cornerwest;
-		x_grid_max=cornereast;
+		x_grid_min=x_grid[0]; x_grid_max=x_grid[ncols-1];
 	}
-	if (yposting>0){
-		y_grid_min=cornersouth;
-		y_grid_max=cornernorth;
+	if (yflip){
+		y_grid_min=y_grid[nlines-1]; y_grid_max=y_grid[0];
 	}
 	else{
-		y_grid_min=cornernorth;
-		y_grid_max=cornersouth;
+		y_grid_min=y_grid[0]; y_grid_max=y_grid[nlines-1];
 	}
 
@@ -109,4 +115,22 @@
 		if ( (x_tria_min>x_grid_max) || (x_tria_max<x_grid_min) || (y_tria_min>y_grid_max) || (y_tria_max<y_grid_min) ) continue;
 
+		/*Get indices i and j that form a square around the currant triangle*/
+		if (yflip){
+			i1=floor((y_tria_max-y_grid_max)/yposting)-1;
+			i2= ceil((y_tria_min-y_grid_max)/yposting);
+		}
+		else{
+			i1=floor((y_tria_min-y_grid_min)/yposting)-1;
+			i2= ceil((y_tria_max-y_grid_min)/yposting);
+		}
+		if (xflip){
+			j1=floor((x_tria_max-x_grid_max)/xposting)-1;
+			j2= ceil((x_tria_min-x_grid_max)/xposting);
+		}
+		else{
+			j1=floor((x_tria_min-x_grid_min)/xposting)-1;
+			j2= ceil((x_tria_max-x_grid_min)/xposting);
+		}
+
 		/*get area of the current element (Jacobian = 2 * area)*/
 		//area =x2 * y3 - y2*x3 + x1 * y2 - y1 * x2 + x3 * y1 - y3 * x1;
@@ -115,12 +139,11 @@
 		  +  x_mesh[(int)index_mesh[3*n+2]-1]*y_mesh[(int)index_mesh[3*n+0]-1]-y_mesh[(int)index_mesh[3*n+2]-1]*x_mesh[(int)index_mesh[3*n+0]-1];
 
-
 		/*Go through x_grid and y_grid and interpolate if necessary*/
-		for (i=0;i<nlines;i++){
+		for (i=i1;i<=i2;i++){
 
 			//exit if y not between y_tria_min and y_tria_max
 			if((y_grid[i]>y_tria_max) || (y_grid[i]<y_tria_min)) continue;
 
-			for(j=0;j<ncols; j++){
+			for(j=j1;j<=j2; j++){
 
 				//exit if x not between x_tria_min and x_tria_max