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+/** CSci-4611 Assignment 6: Harold
+ */
+
+#include "ground.h"
+
+
+Ground::Ground() : diffuse_ramp_(GL_CLAMP_TO_EDGE),
+    specular_ramp_(GL_CLAMP_TO_EDGE), light_pos_(30,30,30)
+{
+    
+}
+
+Ground::~Ground() {
+    
+}
+
+Mesh* Ground::mesh_ptr() { return &ground_mesh_; }
+
+
+void Ground::Init(const std::vector<std::string> &search_path) {
+    // init ground geometry, a simple grid is used.  if it is running too slow,
+    // you can turn down the resolution by decreasing nx and ny, but this will
+    // make the hills look more jaggy.
+    const int nx = 150;
+    const int ny = 150;
+    const float size = 100.0;
+    std::vector<Point3> verts;
+    std::vector<Vector3> norms;
+    for (int j = 0; j <= ny; j++) {
+        for (int i = 0; i <= nx; i++) {
+            float x = size*(float)j/nx - size/2.0f;
+            float y = size*(float)i/ny - size/2.0f;
+            verts.push_back(Point3(x, 0, y));
+            norms.push_back(Vector3(0,1,0));
+        }
+    }
+    std::vector<unsigned int> indices;
+    for (int j = 0; j < ny; j++) {
+        for (int i = 0; i < nx; i++) {
+            // L\ triangle
+            indices.push_back((i+0)+(j+0)*(nx+1));
+            indices.push_back((i+1)+(j+0)*(nx+1));
+            indices.push_back((i+0)+(j+1)*(nx+1));
+            // \7 triangle
+            indices.push_back((i+1)+(j+0)*(nx+1));
+            indices.push_back((i+1)+(j+1)*(nx+1));
+            indices.push_back((i+0)+(j+1)*(nx+1));
+        }
+    }
+    ground_mesh_.SetIndices(indices);
+    ground_mesh_.SetVertices(verts);
+    ground_mesh_.SetNormals(norms);
+    ground_mesh_.UpdateGPUMemory();
+    ground_edge_mesh_.CreateFromMesh(ground_mesh_);
+
+    
+    // load textures and shaders
+    diffuse_ramp_.InitFromFile(Platform::FindFile("toonDiffuse.png", search_path));
+    specular_ramp_.InitFromFile(Platform::FindFile("toonSpecular.png", search_path));
+    
+    artsy_shaderprog_.AddVertexShaderFromFile(Platform::FindFile("artsy.vert", search_path));
+    artsy_shaderprog_.AddFragmentShaderFromFile(Platform::FindFile("artsy.frag", search_path));
+    artsy_shaderprog_.LinkProgram();
+    
+    outline_shaderprog_.AddVertexShaderFromFile(Platform::FindFile("outline.vert", search_path));
+    outline_shaderprog_.AddFragmentShaderFromFile(Platform::FindFile("outline.frag", search_path));
+    outline_shaderprog_.LinkProgram();
+}
+
+
+
+
+// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+// device coordinates) to a 3D point on the ground.  Returns true and sets ground_point
+// to be equal to the result if the conversion is successful.  Returns false if
+// the screen point does not project onto the ground.
+bool Ground::ScreenPtHitsGround(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                              const Point2 &normalized_screen_pt, Point3 *ground_point)
+{
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    
+    Point3 pt3d = GfxMath::ScreenToNearPlane(view_matrix, proj_matrix, normalized_screen_pt);
+    Ray ray(eye, (pt3d - eye).ToUnit());
+    float i_time;
+    int i_tri;
+    return ray.FastIntersectMesh(&ground_mesh_, &i_time, ground_point, &i_tri);
+}
+
+
+
+
+/** This implements the "h" term used in the equations described in section 4.5 of the
+ paper. Three arguments are needed:
+ 1. projection_plane_normal: We need to know where the projection plane is in 3-space
+    Since a plane can be defined by a point within the plane and a normal, we use
+    this normal together with the 3rd argument to the function to define the projection
+    plane described in the paper.
+ 2. silhouette_curve: As described in the paper, the silhouette curve is a 3D version
+    of the curve the user draws with the mouse.  It is formed by projecting the
+    original 2D screen-space curve onto the 3D projection plane.
+ 3. closest_pt_in_plane: As described in the paper, this is the closest point within
+    the projection plane to the vertex of the mesh that we want to modify.  In other
+    words, it is the perpendicular projection of the vertex we want to modify onto
+    the projection plane.
+ */
+float hfunc(const Vector3 projection_plane_normal, const std::vector<Point3> &silhouette_curve, const Point3 &closest_pt_in_plane) {
+    // define the y axis for a "plane space" coordinate system as a world space vector
+    Vector3 plane_y = Vector3(0,1,0);
+    // define the x axis for a "plane space" coordinate system as a world space vector
+    Vector3 plane_x = plane_y.Cross(projection_plane_normal).ToUnit();
+    // define the origin for a "plane space" coordinate system as the first point in the curve
+    Point3 origin = silhouette_curve[0];
+    
+    // loop over line segments in the curve, find the one that lies over the point by
+    // comparing the "plane space" x value for the start and end of the line segment
+    // to the "plane space" x value for the closest point to the vertex that lies
+    // in the projection plane.
+    float x_target = (closest_pt_in_plane - origin).Dot(plane_x);
+    for (int i=1; i<silhouette_curve.size(); i++) {
+        float x_start = (silhouette_curve[(size_t)i-1] - origin).Dot(plane_x);
+        float x_end = (silhouette_curve[i] - origin).Dot(plane_x);
+        if ((x_start <= x_target) && (x_target <= x_end)) {
+            float alpha = (x_target - x_start) / (x_end - x_start);
+            float y_curve = silhouette_curve[(size_t)i-1][1] + alpha*(silhouette_curve[i][1] - silhouette_curve[(size_t)i-1][1]);
+            return y_curve - closest_pt_in_plane[1];
+        }
+        else if ((x_end <= x_target) && (x_target <= x_start)) {
+            float alpha = (x_target - x_end) / (x_start - x_end);
+            float y_curve = silhouette_curve[i][1] + alpha*(silhouette_curve[(size_t)i-1][1] - silhouette_curve[i][1]);
+            return y_curve - closest_pt_in_plane[1];
+        }
+    }
+    
+    // here return 0 because the point does not lie under the curve.
+    return 0.0;
+}
+
+
+
+
+/// Modifies the vertices of the ground mesh to create a hill or valley based
+/// on the input stroke.  The 2D path of the stroke on the screen is passed
+/// in, this is the centerline of the stroke mesh that is actually drawn on
+/// the screen while the user is drawing.
+void Ground::ReshapeGround(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                           const std::vector<Point2> &stroke2d)
+{
+    // TODO: Deform the 3D ground mesh according to the algorithm described in the
+    // Cohen et al. Harold paper.
+    
+    // You might need the eye point and the look vector, these can be determined
+    // from the view matrix as follows:
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    Vector3 look = -camera_matrix.ColumnToVector3(2);
+    
+    
+    
+    // There are 3 major steps to the algorithm, outlined here:
+    
+    // 1. Define a plane to project the stroke onto.  The first and last points
+    // of the stroke are guaranteed to project onto the ground plane.  The plane
+    // should pass through these two points on the ground.  The plane should also
+    // have a normal vector that points toward the camera and is parallel to the
+    // ground plane.
+
+    
+    
+    
+    
+    // 2. Project the 2D stroke into 3D so that it lies on the "projection plane"
+    // defined in step 1.
+    
+    
+    
+    
+    
+    // 3. Loop through all of the vertices of the ground mesh, and adjust the
+    // height of each based on the equations in section 4.5 of the paper, also
+    // repeated in the assignment handout.  The equations rely upon a function
+    // h(), and we have implemented that for you as hfunc() defined above in
+    // this file.  The basic structure of the loop you will need is here:
+    std::vector<Point3> new_verts;
+    for (int i=0; i<ground_mesh_.num_vertices(); i++) {
+        Point3 P = ground_mesh_.read_vertex_data(i); // original vertex
+
+        // adjust P according to equations...
+        
+        
+        
+        
+        
+        new_verts.push_back(P);
+    }
+    ground_mesh_.SetVertices(new_verts);
+    ground_mesh_.CalcPerVertexNormals();
+    ground_mesh_.UpdateGPUMemory();
+    ground_edge_mesh_.CreateFromMesh(ground_mesh_);
+}
+
+
+
+
+/// Draws the ground mesh with toon shading
+void Ground::Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix, const Color &ground_color) {
+    // Lighting parameters
+    Color Ia(1.0f, 1.0f, 1.0f, 1.0f);
+    Color Id(1.0f, 1.0f, 1.0f, 1.0f);
+    Color Is(1.0f, 1.0f, 1.0f, 1.0f);
+    
+    // Material parameters
+    Color ka = ground_color;
+    Color kd(0.4f, 0.4f, 0.4f, 1.0f);
+    Color ks(0.6f, 0.6f, 0.6f, 1.0f);
+    float s = 50.0f;
+    
+    // Precompute matrices needed in the shader
+    Matrix4 model_matrix; // identity
+    Matrix4 modelview_matrix = view_matrix * model_matrix;
+    Matrix4 normal_matrix = modelview_matrix.Inverse().Transpose();
+    Point3 light_in_eye_space = view_matrix * light_pos_;
+    
+    // Make sure the default option to only draw front facing triangles is set
+    glEnable(GL_CULL_FACE);
+    
+    
+    // Draw the ground using the artsy shader
+    artsy_shaderprog_.UseProgram();
+    artsy_shaderprog_.SetUniform("modelViewMatrix", modelview_matrix);
+    artsy_shaderprog_.SetUniform("normalMatrix", normal_matrix);
+    artsy_shaderprog_.SetUniform("projectionMatrix", proj_matrix);
+    artsy_shaderprog_.SetUniform("ka", ka);
+    artsy_shaderprog_.SetUniform("kd", kd);
+    artsy_shaderprog_.SetUniform("ks", ks);
+    artsy_shaderprog_.SetUniform("s", s);
+    artsy_shaderprog_.SetUniform("lightPosition", light_in_eye_space);
+    artsy_shaderprog_.SetUniform("Ia", Ia);
+    artsy_shaderprog_.SetUniform("Id", Id);
+    artsy_shaderprog_.SetUniform("Is", Is);
+    artsy_shaderprog_.BindTexture("diffuseRamp", diffuse_ramp_);
+    artsy_shaderprog_.BindTexture("specularRamp", specular_ramp_);
+    ground_mesh_.Draw();
+    artsy_shaderprog_.StopProgram();
+    
+    // And, draw silhouette edges for the ground using the outline shader
+    glDisable(GL_CULL_FACE);
+    glEnable(GL_POLYGON_OFFSET_FILL);
+    glPolygonOffset(1,1);
+    static const float thickness = 0.2f;
+    outline_shaderprog_.UseProgram();
+    outline_shaderprog_.SetUniform("modelViewMatrix", modelview_matrix);
+    outline_shaderprog_.SetUniform("normalMatrix", normal_matrix);
+    outline_shaderprog_.SetUniform("projectionMatrix", proj_matrix);
+    outline_shaderprog_.SetUniform("thickness", thickness);
+    ground_edge_mesh_.Draw();
+    outline_shaderprog_.StopProgram();
+    
+
+    
+    // This can be useful for debugging, but it is extremely slow to draw.
+    // Before uncommenting this, it's recommended to turn down the resolution
+    // of the ground mesh by adjusting the nx and ny constants inside Init().
+    /**
+     // draw lines around each triangle
+     for (int t=0; t<ground_mesh_.num_triangles(); t++) {
+         std::vector<unsigned int> indices = ground_mesh_.triangle_vertices(t);
+         std::vector<Point3> loop;
+         loop.push_back(ground_mesh_.vertex(indices[0]));
+         loop.push_back(ground_mesh_.vertex(indices[1]));
+         loop.push_back(ground_mesh_.vertex(indices[2]));
+         qs_.DrawLines(model_matrix, view_matrix, proj_matrix, Color(0.7,0.7,0.7), loop, QuickShapes::LinesType::LINE_LOOP, 0.01);
+     }
+     
+     // draw normals
+     for (int i=0; i<ground_mesh_.num_vertices(); i++) {
+         Point3 p1 = ground_mesh_.vertex(i);
+         Point3 p2 = p1 + 0.5*ground_mesh_.normal(i);
+         qs_.DrawLineSegment(model_matrix, view_matrix, proj_matrix, Color(0.7,0.7,0.7), p1, p2, 0.01);
+     }
+    **/
+}
+