Fix for ghosts being rendered in correct order

ghost.cpp

@@ -107,3 +107,7 @@ float rand_float(float rmin, float rmax) {
     float res = (float)rand()/(float)RAND_MAX;
     return res * rdiff + rmin;
 }
+
+glm::vec3 Ghost::get_pos() const {
+    return pos;
+}

ghost.h

@@ -8,6 +8,7 @@ class Ghost {
         Ghost(float xmin, float xmax, float zmin, float zmax);
         void apply_movement(float curr_time, float timed);
         glm::mat4 get_model(glm::vec3 &camera_pos);
+        glm::vec3 get_pos() const;
 
     private:
         int ghost_id;

ghostland.cpp

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include <stdlib.h>
 #include <stdio.h>
 #include "glad/glad.h"
@@ -60,8 +61,7 @@ float *wall_vertices;
 
 int trailmax = 1800;
 
-int main(int argc, char *argv[])
-{
+int main(int argc, char *argv[]) {
 
     int success;
     glm::vec3 position;
@@ -343,7 +343,7 @@ int main(int argc, char *argv[])
         ghosts.push_back(new Ghost(xmin_wall, xmax_wall, zmin_wall, zmax_wall));
     }
 
-    player->mouse_callback(window, 0.0f, WINDOWHEIGHT);
+    player->mouse_callback(window, WINDOWWIDTH/2, WINDOWHEIGHT);
 
     int FPS = -1;
 
@@ -353,7 +353,7 @@ int main(int argc, char *argv[])
         int current_frameI = (int)current_frame;
         if (current_frameI != time_secI) {  // show stats every second
             FPS = num_frames;
-            glm::vec3 player_pos = player->get_position();
+            glm::vec3 player_pos = player->get_pos();
             float yaw, pitch;
             yaw = player->get_yaw();
             pitch = player->get_pitch();
@@ -468,7 +468,20 @@ int main(int argc, char *argv[])
 
         set_uniform(ghost_program, projectionC, projection);
         set_uniform(ghost_program, viewC, view);
-        for (int i = 0; i < ghosts.size(); i++) {
+
+        struct {
+            bool operator()(const Ghost *a, const Ghost *b) const {
+                glm::vec3 a_diff, b_diff;
+                a_diff = player->get_pos() - a->get_pos();
+                b_diff = player->get_pos() - b->get_pos();
+                float a_dist2, b_dist2;
+                a_dist2 = a_diff.x * a_diff.x + a_diff.y * a_diff.y + a_diff.z * a_diff.z;
+                b_dist2 = b_diff.x * b_diff.x + b_diff.y * b_diff.y + b_diff.z * b_diff.z;
+                return a_dist2 < b_dist2;
+            }
+        } ghost_compare;
+        std::sort(ghosts.begin(), ghosts.end(), ghost_compare);
+        for (int i = ghosts.size()/5; i >= 0; i--) {
             glm::mat4 ghost_model = ghosts[i]->get_model(camera_pos);
             ghosts[i]->apply_movement(current_frame, timed);
             set_uniform(ghost_program, modelC, ghost_model);

player.cpp

@@ -22,27 +22,27 @@ Player::Player(glm::vec3 startpos, float startyaw) {
 
 }
 
-glm::vec3 Player::get_position() {
+glm::vec3 Player::get_pos() const {
     return position;
 }
 
-glm::vec3 Player::get_camera_front() {
+glm::vec3 Player::get_camera_front() const {
     return camera_front;
 }
 
-glm::vec3 Player::get_camera_up() {
+glm::vec3 Player::get_camera_up() const {
     return camera_up;
 }
 
-glm::vec3 Player::get_camera_pos() {
+glm::vec3 Player::get_camera_pos() const {
     return position + camera_offset;
 }
 
-glm::vec3 Player::get_light_pos() {
+glm::vec3 Player::get_light_pos() const {
     return get_camera_pos() + get_light_front() * armlength;
 }
 
-glm::vec3 Player::get_light_front() {
+glm::vec3 Player::get_light_front() const {
     float yawp = yaw + light_xpersist;
     float pitchp = pitch + light_ypersist;
     glm::vec3 front;
@@ -318,3 +318,4 @@ void Player::scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
         fov = 90.0f;
     }
 }
+

player.h

@@ -6,6 +6,7 @@
 #include <string>
 
 #include "collisions.h"
+#include "ghost.h"
 
 const float lightoffsetmax = 15.0;
 const float light_persist_factor = 0.99;
@@ -24,12 +25,12 @@ class Player {
         int num_walls;
         float *wall_vertices;
 
-        glm::vec3 get_position();
-        glm::vec3 get_camera_front();
-        glm::vec3 get_camera_up();
-        glm::vec3 get_camera_pos();
-        glm::vec3 get_light_pos();
-        glm::vec3 get_light_front();
+        glm::vec3 get_pos() const;
+        glm::vec3 get_camera_front() const;
+        glm::vec3 get_camera_up() const;
+        glm::vec3 get_camera_pos() const;
+        glm::vec3 get_light_pos() const;
+        glm::vec3 get_light_front() const;
         float get_yaw();
         float get_pitch();
         float get_fov();
@@ -40,6 +41,8 @@ class Player {
         bool is_in_air();
         void apply_movement(float timed);
 
+        bool operator()(const Ghost &a, const Ghost &b) const;
+
     private:
         float yaw;
         float pitch;