diff --git a/lib/ext/render.js b/lib/ext/render.js
index bb3fbf8..bdf5e99 100644
--- a/lib/ext/render.js
+++ b/lib/ext/render.js
@@ -396,12 +396,12 @@ exports.requireExt = function(display, callback)
                 {
                     format += 'llllll';
                     //TODO: Array.copy
-                    params.push(floatToFix(tris[i*6 + 0])); // x1
-                    params.push(floatToFix(tris[i*6 + 1])); // y1
-                    params.push(floatToFix(tris[i*6 + 2])); // x2
-                    params.push(floatToFix(tris[i*6 + 3])); // y2
-                    params.push(floatToFix(tris[i*6 + 4])); // x3
-                    params.push(floatToFix(tris[i*6 + 5])); // y3
+                    params.push(floatToFix(tris[i + 0])); // x1
+                    params.push(floatToFix(tris[i + 1])); // y1
+                    params.push(floatToFix(tris[i + 2])); // x2
+                    params.push(floatToFix(tris[i + 3])); // y2
+                    params.push(floatToFix(tris[i + 4])); // x3
+                    params.push(floatToFix(tris[i + 5])); // y3
                 }
                 X.pack_stream.pack(format, params);
                 X.pack_stream.flush();