add multiple samples per pixel

in_one_weekend/src/camera.zig

@@ -0,0 +1,36 @@
+const Point3 = @import("vec3.zig").Point3;
+const Vec3 = @import("vec3.zig").Vec3;
+const Ray = @import("ray.zig").Ray;
+
+pub const Camera = struct {
+    origin: Point3,
+    lowerLeftCorner: Point3,
+    horizontal: Vec3,
+    vertical: Vec3,
+
+    pub fn init() Camera {
+        const aspectRatio = 16.0 / 9.0;
+        const viewportHeight = 2.0;
+        const viewportWidth = aspectRatio * viewportHeight;
+        const focalLength = 1.0;
+
+        const origin = Vec3{};
+        const horizontal = Vec3{ .x = viewportWidth };
+        const vertical = Vec3{ .y = viewportHeight };
+        const lowerLeftCorner = origin.sub(horizontal.div(2)).sub(vertical.div(2)).sub(Vec3{ .z = focalLength });
+
+        return Camera {
+            .origin = origin,
+            .horizontal = horizontal,
+            .vertical = vertical,
+            .lowerLeftCorner = lowerLeftCorner,
+        };
+    }
+
+    pub fn getRay(self: Camera, u: f32, v: f32) Ray {
+        return Ray{
+            .origin = self.origin,
+            .direction = self.lowerLeftCorner.add(self.horizontal.mul(u)).add(self.vertical.mul(v)).sub(self.origin),
+        };
+    }
+};