Check depth buffer before texture mapping

src/render.cpp

@@ -84,6 +84,21 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                         && (barycenter[1] >= 0.0f)
                         && (barycenter[2] >= 0.0f))
                 {
+                    // Interpolate 1/z for the z-buffer
+                    float zInv =
+                        1.0f /
+                        ((barycenter[0] * p0.w)
+                         + (barycenter[1] * p1.w)
+                         + (barycenter[2] * p2.w));
+
+
+                    // Compute pixel color if it's closer than what's in the z-buffer
+                    if (zInv > memory.zbuffer[y][x])
+                    {
+                        // Update the depth buffer
+                        memory.zbuffer[y][x] = zInv;
+
+
                         // Interpolate U and V of the texture for this point
                         Texture &texture = textures.data[faces.data[f].materialIndex];
                         UV &uv0 = uvs.data[face.uvIndex[0]];
@@ -163,23 +178,11 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                         color.r *= shading.r;
 
 
-                    // Interpolate 1/z for the z-buffer
+                        // Alpha blend the pixel
-                    float zInv =
-                        1.0f /
-                        ((barycenter[0] * p0.w)
-                         + (barycenter[1] * p1.w)
-                         + (barycenter[2] * p2.w));
-
-
-                    // Draw the pixel if it's closer than what's in the z-buffer
-                    if (zInv > memory.zbuffer[y][x])
-                    {
                         ColorU32 *pixel = (ColorU32*)&buffer.buffer[y*buffer.width+x];
-
                         float alpha = color.a / 255.0f;
                         float alphaDiff = 1.0f - alpha;
 
-                        // Blend new color with the existing color
                         ColorU32 blended =
                         {
                             (uint8_t)((alpha * color.b) + (alphaDiff * pixel->b)),
@@ -188,9 +191,9 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                             (uint8_t)((alpha * color.a) + (alphaDiff * pixel->a))
                         };
 
-                        DrawPixel(buffer.buffer, buffer.width, blended.u32, x, y);
 
-                        memory.zbuffer[y][x] = zInv;
+                        // Draw
+                        DrawPixel(buffer.buffer, buffer.width, blended.u32, x, y);
                     }
                 }
             }