diff --git a/polygon_draw.hh b/polygon_draw.hh
index 5bd02b5..8538447 100644
--- a/polygon_draw.hh
+++ b/polygon_draw.hh
@@ -24,10 +24,10 @@ void DrawPolygon(auto&& points, auto&& Plot) requires std::ranges::input_range<d
             {
                 constexpr std::size_t i = p + (p >= Yindex);
                 // Number of steps = number of scanlines
-                auto a = std::get<i>(*from), b = std::get<i>(*to);
-                if constexpr(i == Xindex || !PerspectiveCorrected) return Slope(a,     b, num_steps);
-                else if constexpr(i == Zindex)                     return Slope(1/a, 1/b, num_steps);
-                else return Slope(a / std::get<Zindex>(*from), b / std::get<Zindex>(*to), num_steps);
+                auto a = std::get<i>(*from), b = std::get<i>(*to); // Y coordinate for begin and end
+                if constexpr(i == Xindex || !PerspectiveCorrected) return Slope(a,     b, num_steps, .5f); // Affine interp: X
+                else if constexpr(i == Zindex)                     return Slope(1/a, 1/b, num_steps, .5f); // Z interp
+                else return Slope(a / std::get<Zindex>(*from), b / std::get<Zindex>(*to), num_steps, .5f); // Perspective interp
             });
         },
         // Scanline function
@@ -37,7 +37,7 @@ void DrawPolygon(auto&& points, auto&& Plot) requires std::ranges::input_range<d
             auto leftx = left[Xprop].get();
             auto endx = right[Xprop].get();
             auto num_steps = endx - leftx;
-            auto rounding_error = int(leftx)-leftx;
+            auto intleftx = std::floor(leftx+.5f), rounding_error = intleftx - leftx + .5f;
 
             // For each prop except X coordinate, create slopes between left and right edge
             auto props = [&]<std::size_t...p>(std::index_sequence<p...>, auto&& GetSlope)
@@ -49,7 +49,7 @@ void DrawPolygon(auto&& points, auto&& Plot) requires std::ranges::input_range<d
                 return Slope( std::get<i>(left).get(), std::get<i>(right).get(), num_steps, rounding_error );
             });
             // Using those slopes, render each pixel. After each pixel, update the slopes by their step-sizes.
-            for(int x = leftx, e = endx; x < e; ++x)
+            for(int x = intleftx, e = endx+.5f; x < e; ++x)
             {
                 [&]<std::size_t...p>(std::index_sequence<p...>, auto&& GetValue)
                 {