Normals to hide faces with shading

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

main.cpp

@@ -37,6 +37,8 @@ private:
 	mesh meshCube;
 	mat4x4 matProj;
 
+	vec3d vCamera={0,0,0};
+
 	float fTheta=0;
 
 	void MultiplyMatrixVector(vec3d &i, vec3d &o, mat4x4 &m)
@@ -158,7 +160,19 @@ public:
 			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) {
+			if (normal.x*(triTranslated.p[0].x-vCamera.x)+
+				normal.y*(triTranslated.p[0].y-vCamera.y)+
+				normal.z*(triTranslated.p[0].z-vCamera.z)<0) {
+
+				vec3d light_dir = {0,0,-1};
+				float l = sqrtf(light_dir.x*light_dir.x+light_dir.y*light_dir.y+light_dir.z*light_dir.z);
+				light_dir.x/=l;light_dir.y/=l;light_dir.z/=l;
+
+				float dp = normal.x*(light_dir.x-vCamera.x)+
+					normal.y*(light_dir.y-vCamera.y)+
+					normal.z*(light_dir.z-vCamera.z);
+
+
 				// Project triangles from 3D --> 2D
 				MultiplyMatrixVector(triTranslated.p[0], triProjected.p[0], matProj);
 				MultiplyMatrixVector(triTranslated.p[1], triProjected.p[1], matProj);
@@ -176,7 +190,7 @@ public:
 				triProjected.p[2].y *= 0.5f * (float)ScreenHeight();
 
 				// Rasterize triangle
-				SetDecalMode(DecalMode::WIREFRAME);
+				//SetDecalMode(DecalMode::WIREFRAME);
 				DrawPolygonDecal(nullptr,{
 					{triProjected.p[0].x, triProjected.p[0].y},
 					{triProjected.p[1].x, triProjected.p[1].y},
@@ -185,7 +199,7 @@ public:
 					{0,0},
 					{0,0},
 					{0,0},
-				});
+				},Pixel(255*dp*dp,255*dp*dp,255*dp*dp));
 			}
 
 		}