From de68ccac0d404bd05d82c4cd1e51a292e13592d2 Mon Sep 17 00:00:00 2001
From: przmk <przemek@gasinski.eu>
Date: Sat, 27 Jul 2024 13:46:50 +0200
Subject: [PATCH] Add simple FPS cap

---
 src/main.zig | 64 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 55 insertions(+), 9 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 6849649..f0df9ff 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -6,6 +6,52 @@ const zm = @import("zmath");
 const VulkanRenderer = @import("vulkan_renderer.zig").VulkanRenderer;
 const Vector3 = @import("utilities.zig").Vector3;
 
+// 100 fps
+const TARGET_MS_F32: f32 = 16.0;
+
+const Delta = struct {
+    current_time: u64 = 0,
+    last_time: u64 = 0,
+
+    delta_ms: u64 = 0,
+    delta_f32: f32 = 0.0,
+
+    delay_amount: u32 = 0,
+
+    perf_frequency: f64,
+
+    _counter: u32 = 0,
+
+    pub fn new() Delta {
+        return .{
+            .perf_frequency = @as(f64, @floatFromInt(sdl.getPerformanceFrequency())),
+        };
+    }
+
+    pub fn start(self: *Delta) void {
+        self.last_time = sdl.getPerformanceCounter();
+    }
+
+    pub fn tick(self: *Delta) void {
+        self.current_time = sdl.getPerformanceCounter();
+        self.delta_ms = self.current_time - self.last_time;
+
+        const delta_f64 = @as(f64, @floatFromInt(self.delta_ms)) / (self.perf_frequency * 1000.0);
+        self.delta_f32 = @as(f32, @floatCast(delta_f64));
+
+        self.delay_amount = @as(u32, @intFromFloat(@floor(TARGET_MS_F32 - self.delta_f32)));
+
+        // Limit the output to the terminal
+        if (self._counter % 100 == 0) {
+            const fps = self.perf_frequency / @as(f64, @floatFromInt(self.delta_ms));
+            std.debug.print("ms/f: {d}\tFPS: {d}\n", .{ delta_f64 * 1000.0, fps });
+        }
+
+        self.last_time = self.current_time;
+        self._counter += 1;
+    }
+};
+
 pub fn main() !void {
     const window = try initWindow();
     defer sdl.quit();
@@ -19,10 +65,10 @@ pub fn main() !void {
     var vulkan_renderer = try VulkanRenderer.init(window, allocator);
     defer vulkan_renderer.deinit();
 
+    var delta = Delta.new();
+    delta.start();
+
     var angle: f32 = 0.0;
-    var now: u64 = sdl.getPerformanceCounter();
-    var last: u64 = 0;
-    var delta_time: f32 = 0.0;
 
     mainLoop: while (true) {
         while (sdl.pollEvent()) |ev| {
@@ -37,11 +83,9 @@ pub fn main() !void {
             }
         }
 
-        last = now;
-        now = sdl.getPerformanceCounter();
-        delta_time = @as(f32, @floatFromInt(now - last)) * 1000.0 / @as(f32, @floatFromInt(now));
+        delta.tick();
 
-        angle += 10.0 * delta_time;
+        angle += 200.0 * delta.delta_f32;
 
         if (angle > 360.0) {
             angle -= 360.0;
@@ -50,13 +94,15 @@ pub fn main() !void {
         var first_model = zm.rotationZ(angle);
         var second_model = zm.rotationZ(-angle * 2);
 
-        first_model = zm.mul(first_model, zm.translation(0.0, 0.0, -2.5));
-        second_model = zm.mul(second_model, zm.translation(0.0, 0.0, -4.5));
+        first_model = zm.mul(first_model, zm.translation(1.0, 0.0, -2.5));
+        second_model = zm.mul(second_model, zm.translation(-1.0, 0.0, -4.5));
 
         try vulkan_renderer.updateModel(0, first_model);
         try vulkan_renderer.updateModel(1, second_model);
 
         try vulkan_renderer.draw();
+
+        sdl.delay(delta.delay_amount);
     }
 }