diff --git a/c3d.c b/c3d.c
index ab98fba..f13f10f 100644
--- a/c3d.c
+++ b/c3d.c
@@ -168,7 +168,10 @@ void FillTopFlatZbuffer(Zee *zee, Tri2D *t, Tri2D *tp) {
     double curx1 = t->c.x;
     double curx2 = t->c.x;
 
-    for (int scanline = t->c.y; scanline >= t->a.y; scanline--) {
+	int scanbottom = t->c.y;
+	int scantop = Max(t->a.y, 0);
+
+    for (int scanline = scanbottom; scanline >= scantop; scanline--) {
         if (0 <= scanline && scanline < RENDERHEIGHT) {
 
 			DrawScanline(zee, tp, curx1, curx2, scanline);
@@ -206,7 +209,10 @@ void FillBottomFlatZbuffer(Zee *zee, Tri2D *t, Tri2D *tp) {
     double curx1 = t->a.x;
     double curx2 = t->a.x;
 
-    for (int scanline = t->a.y; scanline < t->c.y;
+	int scantop = t->a.y; // start must always be the true beging of the triangle, otherwise everything will be offset
+	int scanbottom = Min(t->c.y, RENDERHEIGHT); // we can stop rendering as soon as it goes off screen
+
+    for (int scanline = scantop; scanline < scanbottom;
          scanline++) { // TODO: Possibly more optimization possible here, use linear correspondance
                        // for y, not just x to get depth
         if (0 <= scanline && scanline < RENDERHEIGHT) {