Compute X incrementally

1 files changed, 3 insertions, 2 deletions

diff --git a/dda.c b/dda.c
index 9e7db61..91357ee 100644
--- a/dda.c
+++ b/dda.c
@@ -56,13 +56,12 @@ dda (test_data_t *testdata)
     double y1 = testdata->segment.y1;
     int i = 0;
 
-
     double dxdy = (x1 - x0) / (y1 - y0);
     double y = next_sample_y (y0);
+    double x = (y - y0) * dxdy + x0;
 
     while (y < next_sample_y (y1))
     {
-	double x = (y - y0) * dxdy + x0;
 	double xi = next_sample_x (x);
 
 	if (testdata->points[i++] != xi		||
@@ -72,6 +71,8 @@ dda (test_data_t *testdata)
 	    exit (-1);
 	}
 
+	x += sample_step_y (y) * dxdy;
+
 	y += sample_step_y (y);
     }
 }