added getNormalAt() to Shape & Sphere, trying to get basic lighting

git-svn-id: svn://anubis/fart/trunk@44 7f9b0f55-74a9-4bce-be96-3c2cd072584d

main/Scene.cc

@@ -132,9 +132,16 @@ void Scene::renderPixel(int x, int y, unsigned char * pixel)
 
         if (intersections.numResults > 0)
         {
-            pixel[BMP_RED] = 0xFF;
-            pixel[BMP_GREEN] = 0xFF;
-            pixel[BMP_BLUE] = 0xFF;
+            Vector local_intersection_point =
+                transformed_ray[intersections.results[0]];
+            Vector normal = (*it)->getNormalAt(local_intersection_point);
+            double dot = -(normal % transformed_ray.getDirection());
+            cout << "got dot " << dot << endl;
+            if (dot < 0.0)
+                dot = 0.0;
+            pixel[BMP_RED] = (unsigned char) (0xFF * dot);
+            pixel[BMP_GREEN] = (unsigned char) (0xFF * dot);
+            pixel[BMP_BLUE] = (unsigned char) (0xFF * dot);
         }
         else
         {

shapes/Shape.h

@@ -4,6 +4,7 @@
 
 #include "util/Solver.h"
 #include "util/Ray.h"
+#include "util/Vector.h"
 #include "util/Transform.h"
 
 class Shape
@@ -12,6 +13,7 @@ class Shape
         virtual Solver::Result intersect(const Ray & ray) = 0;
         void setTransform(const Transform & t) { m_transform = t; }
         Transform & getTransform() { return m_transform; }
+        virtual Vector getNormalAt(const Vector & pt) = 0;
 
     protected:
         Transform m_transform;

shapes/Sphere.cc

@@ -34,3 +34,9 @@ Solver::Result Sphere::intersect(const Ray & ray)
     }
     return res;
 }
+
+Vector Sphere::getNormalAt(const Vector & pt)
+{
+    Vector normal = pt;
+    return normal.normalize();
+}

shapes/Sphere.h

@@ -9,6 +9,7 @@ class Sphere : public Shape
     public:
         Sphere(double radius);
         Solver::Result intersect(const Ray & ray);
+        Vector getNormalAt(const Vector & pt);
 
     private:
         double m_radius;

util/Vector.cc

@@ -26,14 +26,14 @@ Vector & Vector::normalize()
     return *this;
 }
 
-double Vector::mag()
+double Vector::mag() const
 {
     return sqrt(m_array[0] * m_array[0]
               + m_array[1] * m_array[1]
               + m_array[2] * m_array[2]);
 }
 
-double Vector::mag2()
+double Vector::mag2() const
 {
     return m_array[0] * m_array[0]
          + m_array[1] * m_array[1]

util/Vector.h

@@ -12,8 +12,8 @@ class Vector
         double & operator[](int idx) { return m_array[idx]; }
         double operator[](int idx) const { return m_array[idx]; }
         Vector & normalize();
-        double mag();
-        double mag2();
+        double mag() const;
+        double mag2() const;
 
     private:
         double  m_array[3];