Feature : Draw charges on the window.

charge.c

+/**
+ * @file charge.c
+ * @author Tanguy Cavagna (tanguy.cavagna@etu.hesge.ch)
+ * @brief Chrage library
+ * @version 0.1
+ * @date 2021-07-12
+ * 
+ * @copyright Copyright (c) 2021
+ * 
+ */
+#include "draw/draw.h"
+#include "vector/vector.h"
+#include "utils.h"
+#include "charge.h"
+
+bool compute_e(charge_t c, vec2 p, double eps, vec2 *e) {
+}
+
+bool compute_total_normalized_e(charge_t *charges, int num_charges, vec2 p, double eps, vec2 *e) {
+}
+
+bool draw_field_line(struct gfx_context_t *ctxt, charge_t *charges, int num_charges, double dx, vec2 pos0, double x0, double x1, double y0, double y1) {
+}
+
+void draw_charges(struct gfx_context_t *ctxt, charge_t *charges, int num_charges, double x0, double x1, double y0, double y1) {
+    // Center coordinates
+    coordinates_t c;
+
+    // Charges coordinates
+    coordinates_t ch0;
+    coordinates_t ch1;
+
+    int radius = 45;
+    int chargePadding = 10;
+
+    // Draw charges
+    for (int i = 0; i < num_charges; i++) {
+        coordinates_t chCoord = position_to_coordinates(ctxt->width, ctxt->height, x0, x1, y0, y1, charges[i].pos);
+
+        // Draw sign according to charge value
+        if (charges[i].q < 0) {
+            gfx_draw_line(ctxt, coordinates_create(chCoord.row, chCoord.column - chargePadding), coordinates_create(chCoord.row, chCoord.column + chargePadding), COLOR_BLUE);
+        } else {
+            gfx_draw_line(ctxt, coordinates_create(chCoord.row, chCoord.column - chargePadding), coordinates_create(chCoord.row, chCoord.column + chargePadding), COLOR_RED);
+            gfx_draw_line(ctxt, coordinates_create(chCoord.row - chargePadding, chCoord.column), coordinates_create(chCoord.row + chargePadding, chCoord.column), COLOR_RED);
+        }
+
+        gfx_draw_circle(ctxt, chCoord, radius, charges[i].q < 0 ? COLOR_BLUE : COLOR_RED);
+    }
+}
\ No newline at end of file

charge.h

+/**
+ * @file charge.h
+ * @author Tanguy Cavagna (tanguy.cavagna@etu.hesge.ch)
+ * @brief Charge file header
+ * @version 0.1
+ * @date 2021-07-12
+ * 
+ * @copyright Copyright (c) 2021
+ * 
+ */
+#ifndef _CHARGE_H_
+#define _CHARGE_H_
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include "utils.h"
+#include "vector/vector.h"
+#include "gfx/gfx.h"
+
+/**
+ * @brief Compute E*qP/norm(qP)
+ * 
+ * @param c Parent charge
+ * @param p Point on which to compute e
+ * @param eps Minimal gap between field and charge
+ * @param e Electric field
+ * @return bool false norm(qP) < eps
+ */
+bool compute_e(charge_t c, vec2 p, double eps, vec2 *e);
+
+/**
+ * @brief Compute the normilized sum of Ei*qiP/norm(qiP)
+ * 
+ * @param charges All the charges
+ * @param num_charges Number of charges in action
+ * @param p Current computed point
+ * @param eps Minimal gap between field and charge
+ * @param e Electric field
+ * @return bool false for some qiP, norm(qiP) < eps
+ */
+bool compute_total_normalized_e(charge_t *charges, int num_charges, vec2 p, 
+                                double eps, vec2 *e);
+
+/**
+ * @brief Compute and then draw all the points belonging to a field line,
+ *        starting from pos0
+ * 
+ * @param ctxt Context to draw on
+ * @param charges All the charges
+ * @param num_charges Number of charges in action
+ * @param dx Space between computed points on the field line
+ * @param pos0 First post to start the computing of the field line
+ * @param x0 Minal x of the universe
+ * @param x1 Maximal x of the universe
+ * @param y0 Minal y of the universe
+ * @param y1 Maximal y of the universe
+ * @return bool false if pos0 not a valid pos (e.g. too close to a charge)
+ */
+bool draw_field_line(struct gfx_context_t *ctxt, charge_t *charges, 
+                            int num_charges, double dx, vec2 pos0, double x0, 
+                            double x1, double y0, double y1);
+
+/**
+ * @brief Draw all charges
+ *        A circle with a minus sign for negative charges
+ *        A circle with a plus sign for positive charges
+ * 
+ * @param ctxt Context to draw on
+ * @param charges All the charges
+ * @param num_charges Number of charges in action
+ * @param x0 Minal x of the universe
+ * @param x1 Maximal x of the universe
+ * @param y0 Minal y of the universe
+ * @param y1 Maximal y of the universe
+ */
+void draw_charges(struct gfx_context_t *ctxt, charge_t *charges,
+                         int num_charges, double x0, double x1, double y0, double y1);
+
+#endif // _CHARGE_H_
\ No newline at end of file

main.c

+/**
+ * @file main.c
+ * @author Tanguy Cavagna (tanguy.cavagna@etu.hesge.ch)
+ * @brief Main file for the electric field exercice
+ * @version 0.1
+ * @date 2021-07-12
+ * 
+ * @copyright Copyright (c) 2021
+ * 
+ */
+#include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include <math.h>
 #include "gfx/gfx.h"
+#include "charge.h"
 
-int main(void) {
-    const int WINDOW_SIZE_X = 500;
-    const int WINDOW_SIZE_Y = 500;
+#define WINDOW_WIDTH 500
+#define WINDOW_HEIGHT 500
+#define x0 0 // Minimal x of the universe
+#define x1 1 // Maximal x of the universe
+#define y0 0 // Minimal y of the universe
+#define y1 1 // Maximal y of the universe
+#define NB_CHARGES 2
 
+int main(void) {
     srand(time(NULL));
 
-    struct gfx_context_t *ctxt = gfx_create("draw", WINDOW_SIZE_X, WINDOW_SIZE_Y);
-
+    // GFX initialization
+    struct gfx_context_t *ctxt = gfx_create("draw", WINDOW_WIDTH, WINDOW_HEIGHT);
     if (!ctxt) {
         fprintf(stderr, "Graphics initialization failed !\n");
         return EXIT_FAILURE;
     }
 
+    charge_t charges[NB_CHARGES];
+    charges[0] = charge_create(10, init_vector(0.25, 0.5));
+    charges[1] = charge_create(-10, init_vector(0.75, 0.5));
+    draw_charges(ctxt, charges, NB_CHARGES, x0, x1, y0, y1);
+
+    // GFX Draw loop
     while (gfx_keypressed() != SDLK_ESCAPE){
         gfx_present(ctxt);
     }

utils.c

@@ -4,7 +4,7 @@
 #include "utils.h"
 
 // Transform a position in the univers [x0,y0]x[x1,y1] to a screen position
-coordinates_t position_to_coordinates(int width, int height, double x0, double x1, double y0, double y1, vector pos)
+coordinates_t position_to_coordinates(int width, int height, double x0, double x1, double y0, double y1, vec2 pos)
 {
     double dx = x1 - x0;
     double dy = y1 - y0;
@@ -16,7 +16,7 @@ double rand_one()
     return (double)rand() / (double)RAND_MAX;
 }
 
-charge_t charge_create(double q, vector pos)
+charge_t charge_create(double q, vec2 pos)
 {
     charge_t c = {.q = q, .pos = pos};
     return c;

utils.h

@@ -8,17 +8,17 @@
 #include "vector/vector.h"
 #include "draw/draw.h"
 
-typedef struct
+typedef struct _charge_t
 {
     double q;
-    vector pos;
+    vec2 pos;
 } charge_t;
 
 // Transform a position in the univers [x0,y0]x[x1,y1] to a screen position
-coordinates_t position_to_coordinates(int width, int height, double x0, double x1, double y0, double y1, vector pos);
+coordinates_t position_to_coordinates(int width, int height, double x0, double x1, double y0, double y1, vec2 pos);
 
 double rand_one();
 
-charge_t charge_create(double q, vector pos);
+charge_t charge_create(double q, vec2 pos);
 
 #endif
\ No newline at end of file

vector/vector.c

@@ -11,6 +11,12 @@
 #include <stdio.h>
 #include "vector.h"
 
+vec2 init_vector(double x, double y) {
+    vec2 v = {x, y};
+    
+    return v;
+}
+
 /*! \fn vector add_vector(vector v1, vector v2)
     \brief Add two vector and return the final vector
     \param v1 First vector to add

vector/vector.h

@@ -21,6 +21,7 @@ typedef struct {
     double a; /* Angle of the vector */
 } polarVector;
 
+vec2 init_vector(double x, double y); /* Initialize a new vector */
 vec2 add_vector(vec2 v1, vec2 v2); /* Add a vector to another and return the result as a vector */
 vec2 sub_vector(vec2 v1, vec2 v2); /* Substract a vector to another vector and return the result as a vector */
 vec2 mult_by_scalar(vec2 v1, int scalar); /* Multiply a vector by a scalar */