Merge pull request #74 from MrTanoshii/shader-comments

Added comments for shader file and a bit for pathfinding algorithm

src/assets/shaders/lights.glsl

@@ -13,19 +13,41 @@ uniform int obstaclesCount;
 
 bool segmentsIntersection(vec2 first, vec2 second, vec2 third, vec2 fourth)
 {
-    vec3 r = vec3(second - first, 0.0);
-    vec3 s = vec3(fourth - third, 0.0);
-    vec3 first_third = vec3(third - first, 0.0);
+    /*
+    Checks if two segments intersect
+    vec2 first:     x, y of the first end of the first segment
+    vec2 second:    x, y of the second end of the first segment
+    vec2 third:     x, y of the first end of the second segment
+    vec2 fourth:    x, y of the second end of the second segment
 
-    float t_numerator = cross(first_third, s).z;
-    float u_numerator = cross(first_third, r).z;
-    float denominator = cross(r, s).z;
+    return bool:    true if segments intersect, false if not
 
-    if (abs(denominator) <= 1e-8)
-        return false;
+    to get familiar with what's going on here, you can read the following article on wikipedia:
+    https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection#Given_two_points_on_each_line_segment
+    */
+
+    vec3 r = vec3(second - first, 0.0);     // the same as (x2 - x1, y2 - y1) in the article
+    vec3 s = vec3(fourth - third, 0.0);     // the same as (x4 - x3, y4 - y3) in the article
+    vec3 first_third = vec3(third - first, 0.0);    // the same as (x3 - x1, y3 - y1) in the article
+
+    // these three vectors are three-dimensional, because I decided to find determinant using cross-product
+    // of two two-dimensional vectors
+
+    float t_numerator = cross(first_third, s).z;    // numerator of t from the article
+    float u_numerator = cross(first_third, r).z;    // numerator of u from the article
+    float denominator = cross(r, s).z;      // denominator from the article (t and u have the same denominator)
+
+    if (abs(denominator) <= 1e-8)       // if determinant is zero (or approximately equal to), then
+        return false;                   // the segments are parallel therefore do not intersect
 
+    //  then we should test if t and u are in the interval [0, 1], if they are then segments intersecting
+    //  but division is time-consuming operation, doing some math, we can avoid division
+    //  that is what's going on in the lines below
+
+    //  if both numerator and denominator are positive
     if (0.0 <= t_numerator && t_numerator <= denominator && 0.0 <= u_numerator && u_numerator <= denominator)
         return true;
+    //  if both numerator and denominator are negative
     else if (denominator <= t_numerator && t_numerator <= 0.0 && denominator <= u_numerator && u_numerator <= 0.0)
         return true;
     else
@@ -35,6 +57,17 @@ bool segmentsIntersection(vec2 first, vec2 second, vec2 third, vec2 fourth)
 
 bool segmentRectangleIntersection(vec4 segment, vec4 rectangle)
 {
+    /*
+    Checks if given segment intersects given rectangle
+    vec4 segment:   x, y of the first end of the segment and x, y of the second end of the segment
+    vec4 rectangle  x, y of the top left vertex of the rectangle and x, y of the bottom right vertex
+
+    return bool:    true if a segment intersects rectangle else false
+
+    if a line intersects a rectangle, then it intersects at least one of it's diagonal,
+    hence instead of checking four sides, we can check for intersection only diagonals
+    the game draws obstacles after calculating the lights, hence in the end we obtain a nice picture
+    */
     vec4 firstDiagonal = rectangle;
     vec4 secondDiagonal = vec4(rectangle.z, rectangle.y, rectangle.x, rectangle.w);
 
@@ -49,11 +82,18 @@ bool segmentRectangleIntersection(vec4 segment, vec4 rectangle)
 
 float computeLight(vec3 light, vec2 pixelPosition)
 {
+    /*
+    Calculates how much light is in given point
+    vec3 light:         x, y, radius of a light
+    vec2 pixelPosition: x, y of a pixel that we are checking
+
+    return float:       number in interval [0, 1] that tells us how much light in the pixel
+    */
     float _distance = length(light.xy - pixelPosition);
 
     vec4 segment = vec4(light.xy, pixelPosition);
 
-
+    // Check every rectangle (obstacle) on a game plane
     for (int i = 0; i < obstaclesCount; ++i)
         if (segmentRectangleIntersection(segment, obstacles[i].xyzw))
             return 0.0;
@@ -70,8 +110,8 @@ void mainImage( out vec4 fragColor, in vec2 fragCoord )
     for (int i = 0; i < lightCount; ++i)
     {
         float lightAmount = computeLight(lightSources[i].xyz, fragCoord);
-        vec4 color = mix(blackColor, LIGHT_COLOR, lightAmount);
-        preFragColor = mix(preFragColor, color, lightAmount);
+        vec4 color = mix(blackColor, LIGHT_COLOR, lightAmount);     // mix obtained light amount with light color
+        preFragColor = mix(preFragColor, color, lightAmount);       // mix obtained color with color of texture
     }
 
     fragColor = preFragColor;

src/classes/world.py

@@ -97,15 +97,16 @@ def tile_to_screen(self, tile_x: int, tile_y: int) -> tuple[int, int]:
     @lru_cache()
     def pathfinding(self, start: tuple[int, int], destination: tuple[int, int]) -> list[tuple[int, int]] | None:
         """
+        A* algorithm realization
+        Uses manhattan distance as heuristics
+
         :param start: tuple of absolute coordinates of start position
         :param destination: tuple of absolute coordinates of destination position
         :return: list of absolute coordinates or None if path not found
         """
 
         start_tile = self.screen_to_tile(*start)
         destination_tile = self.screen_to_tile(*destination)
-        print(self.grid[destination_tile])
-        print(destination_tile)
 
         lengths = np.full((int(self.map.width), int(self.map.height)), -1)
         lengths[start_tile] = 0