backface culling + gouraud shading

Author: ssloy

main.cpp

@@ -1,6 +1,5 @@
 #include <vector>
 #include <cmath>
-#include <cstdlib> // for rand
 #include "tgaimage.h"
 #include "model.h"
 #include "geometry.h"
@@ -62,14 +61,22 @@ int main(int argc, char** argv) {
     }
 
     TGAImage image(width, height, TGAImage::RGB);
+    Vec3f light_dir(0,0,-1);
     for (int i=0; i<model->nfaces(); i++) {
         std::vector<int> face = model->face(i);
         Vec2i screen_coords[3];
+        Vec3f world_coords[3];
         for (int j=0; j<3; j++) {
-            Vec3f world_coords = model->vert(face[j]);
-            screen_coords[j] = Vec2i((world_coords.x+1.)*width/2., (world_coords.y+1.)*height/2.);
+            Vec3f v = model->vert(face[j]);
+            screen_coords[j] = Vec2i((v.x+1.)*width/2., (v.y+1.)*height/2.);
+            world_coords[j]  = v;
+        }
+        Vec3f n = (world_coords[2]-world_coords[0])^(world_coords[1]-world_coords[0]);
+        n.normalize();
+        float intensity = n*light_dir;
+        if (intensity>0) {
+            triangle(screen_coords[0], screen_coords[1], screen_coords[2], image, TGAColor(intensity*255, intensity*255, intensity*255, 255));
         }
-        triangle(screen_coords[0], screen_coords[1], screen_coords[2], image, TGAColor(rand()%255, rand()%255, rand()%255, 255));
     }
 
     image.flip_vertically(); // i want to have the origin at the left bottom corner of the image