twn_fog.c: fog added!

src/rendering/twn_fog.c

@@ -0,0 +1,34 @@
+#include "twn_rendering.h"
+#include "twn_rendering_c.h"
+#include "twn_util.h"
+
+#include <stdbool.h>
+
+static float start_cache, end_cache, density_cache;
+static Color color_cache;
+static bool fog_used = false;
+
+
+void push_fog(float start, float end, float density, Color color) {
+    start_cache = start;
+    end_cache = end;
+    density_cache = density;
+    color_cache = color;
+    fog_used = true;
+}
+
+
+void apply_fog(void) {
+    if (!fog_used)
+        return;
+
+    finally_apply_fog(start_cache, end_cache, density_cache, color_cache);
+}
+
+
+void pop_fog(void) {
+    if (!fog_used)
+        return;
+
+    finally_pop_fog();
+}