Plate generation.

src/gen.c

@@ -1,6 +1,9 @@
 #include "include/gen.h"
 #include "include/col.h"
 
+#include <stdlib.h>
+#include <time.h>
+
 Vec2 asth[WORLD_SZ][WORLD_SZ] = {
     {
         (Vec2){.x = 1, .y = 2},
@@ -84,10 +87,45 @@ Vec2 asth[WORLD_SZ][WORLD_SZ] = {
     },
 };
 
-Plate lith[NPLATES] = {
-    (Plate){.col = COL_BLU,
-            .nverts = 4,
-            .verts = {(Pt){0, 0}, (Pt){7, 0}, (Pt){7, 5}, (Pt){4, 4}}},
-    (Plate){COL_RED, 4, {(Pt){0, 0}, (Pt){4, 4}, (Pt){2, 7}, (Pt){0, 7}}},
-    (Plate){COL_GRN, 4, {(Pt){4, 4}, (Pt){7, 5}, (Pt){7, 7}, (Pt){2, 7}}},
-};
+Plate lith[NPLATES];
+
+// Find the point for an index to the edge of the world.
+Pt world_edge_idx_to_pt(int idx) {
+    if (0 <= idx && idx < 8) {
+        return (Pt){idx, 0};
+    } else if (8 <= idx && idx < 16) {
+        return (Pt){7, idx - 8};
+    } else if (16 <= idx && idx < 24) {
+        return (Pt){idx - 16, 0};
+    } else if (24 <= idx && idx < 32) {
+        return (Pt){7, idx - 24};
+    } else {
+        exit(122);
+    }
+}
+
+void gen_lith() {
+    srand(time(NULL));
+
+    Pt p1 = {(rand() % 6) + 1, 0};
+    Pt p2 = {(rand() % 6) + 1, 7};
+
+    lith[0] = (Plate){
+        .col = COL_RED,
+        .nverts = 4,
+        .verts = {
+            (Pt){0, 0},
+            p1,
+            p2,
+            (Pt){0, 7},
+        },
+    };
+    lith[1] = (Plate){.col = COL_RED,
+                      .nverts = 4,
+                      .verts = {
+                          p1,
+                          (Pt){7, 0},
+                          (Pt){7, 7},
+                          p2,
+                      }};
+}