Hello Cube

Co-authored-by: sigonasr2 <sigonasr2@gmail.com>

main.cpp

@@ -143,33 +143,50 @@ public:
 			triTranslated.p[1].z = triRotatedZX.p[1].z + 3.0f;
 			triTranslated.p[2].z = triRotatedZX.p[2].z + 3.0f;
 
-			// Project triangles from 3D --> 2D
-			MultiplyMatrixVector(triTranslated.p[0], triProjected.p[0], matProj);
-			MultiplyMatrixVector(triTranslated.p[1], triProjected.p[1], matProj);
-			MultiplyMatrixVector(triTranslated.p[2], triProjected.p[2], matProj);
-
-			// Scale into view
-			triProjected.p[0].x += 1.0f; triProjected.p[0].y += 1.0f;
-			triProjected.p[1].x += 1.0f; triProjected.p[1].y += 1.0f;
-			triProjected.p[2].x += 1.0f; triProjected.p[2].y += 1.0f;
-			triProjected.p[0].x *= 0.5f * (float)ScreenWidth();
-			triProjected.p[0].y *= 0.5f * (float)ScreenHeight();
-			triProjected.p[1].x *= 0.5f * (float)ScreenWidth();
-			triProjected.p[1].y *= 0.5f * (float)ScreenHeight();
-			triProjected.p[2].x *= 0.5f * (float)ScreenWidth();
-			triProjected.p[2].y *= 0.5f * (float)ScreenHeight();
-
-			// Rasterize triangle
-			SetDecalMode(DecalMode::WIREFRAME);
-			DrawPolygonDecal(nullptr,{
-				{triProjected.p[0].x, triProjected.p[0].y},
-				{triProjected.p[1].x, triProjected.p[1].y},
-				{triProjected.p[2].x, triProjected.p[2].y}
-			},{
-				{0,0},
-				{0,0},
-				{0,0},
-			});
+			vec3d normal,line1,line2;
+			line1.x=triTranslated.p[1].x-triTranslated.p[0].x;
+			line1.y=triTranslated.p[1].y-triTranslated.p[0].y;
+			line1.z=triTranslated.p[1].z-triTranslated.p[0].z;
+			line2.x=triTranslated.p[2].x-triTranslated.p[0].x;
+			line2.y=triTranslated.p[2].y-triTranslated.p[0].y;
+			line2.z=triTranslated.p[2].z-triTranslated.p[0].z;
+
+			normal.x=line1.y*line2.z-line1.z*line2.y;
+			normal.y=line1.z*line2.x-line1.x*line2.z;
+			normal.z=line1.x*line2.y-line1.y*line2.x;
+
+			float l = sqrtf(normal.x*normal.x+normal.y*normal.y+normal.z*normal.z);
+			normal.x/=l;normal.y/=l;normal.z/=l;
+
+			if (normal.z<0) {
+				// Project triangles from 3D --> 2D
+				MultiplyMatrixVector(triTranslated.p[0], triProjected.p[0], matProj);
+				MultiplyMatrixVector(triTranslated.p[1], triProjected.p[1], matProj);
+				MultiplyMatrixVector(triTranslated.p[2], triProjected.p[2], matProj);
+
+				// Scale into view
+				triProjected.p[0].x += 1.0f; triProjected.p[0].y += 1.0f;
+				triProjected.p[1].x += 1.0f; triProjected.p[1].y += 1.0f;
+				triProjected.p[2].x += 1.0f; triProjected.p[2].y += 1.0f;
+				triProjected.p[0].x *= 0.5f * (float)ScreenWidth();
+				triProjected.p[0].y *= 0.5f * (float)ScreenHeight();
+				triProjected.p[1].x *= 0.5f * (float)ScreenWidth();
+				triProjected.p[1].y *= 0.5f * (float)ScreenHeight();
+				triProjected.p[2].x *= 0.5f * (float)ScreenWidth();
+				triProjected.p[2].y *= 0.5f * (float)ScreenHeight();
+
+				// Rasterize triangle
+				SetDecalMode(DecalMode::WIREFRAME);
+				DrawPolygonDecal(nullptr,{
+					{triProjected.p[0].x, triProjected.p[0].y},
+					{triProjected.p[1].x, triProjected.p[1].y},
+					{triProjected.p[2].x, triProjected.p[2].y}
+				},{
+					{0,0},
+					{0,0},
+					{0,0},
+				});
+			}
 
 		}