Use stub Vec3 / Color to implement gradient image.

zigrtiow/src/color.zig

@@ -0,0 +1,10 @@
+const std = @import("std");
+const Color = @import("./vec.zig").Color;
+
+pub fn write_color(c: Color) anyerror!void {
+    var ir = @floatToInt(u8, 255.999 * c.x());
+    var ig = @floatToInt(u8, 255.999 * c.y());
+    var ib = @floatToInt(u8, 255.999 * c.z());
+    const stdout = std.io.getStdOut();
+    try stdout.writer().print("{d} {d} {d}\n", .{ ir, ig, ib });
+}

zigrtiow/src/main.zig

@@ -1,7 +1,29 @@
 const std = @import("std");
+const info = std.log.info;
+const vec = @import("./vec.zig");
+const Vec3 = vec.Vec3;
+const Color = vec.Color;
+const write_color = @import("./color.zig").write_color;
 
 pub fn main() anyerror!void {
-    std.log.info("All your codebase are belong to us.", .{});
+    const image_width: isize = 256;
+    const image_height: isize = 256;
+
+    const stdout = std.io.getStdOut();
+
+    info("Writing image {d}x{d}\n", .{ image_width, image_height });
+    try stdout.writer().print("P3\n{d} {d}\n255\n", .{ image_width, image_height });
+
+    var j: isize = image_height - 1;
+    while (j >= 0) : (j -= 1) {
+        info("Scanlines remaining: {d}", .{j});
+
+        var i: isize = 0;
+        while (i < image_width) : (i += 1) {
+            const pixel_color = Color.init(@intToFloat(f32, i) / @intToFloat(f32, image_width - 1), @intToFloat(f32, j) / @intToFloat(f32, image_height - 1), 0.25);
+            try write_color(pixel_color);
+        }
+    }
 }
 
 test "basic test" {

zigrtiow/src/vec.zig

@@ -0,0 +1,19 @@
+pub const Vec3 = struct {
+    v: @Vector(3, f32),
+    pub fn init(v0: f32, v1: f32, v2: f32) Vec3 {
+        return Vec3{
+            .v = .{ v0, v1, v2 },
+        };
+    }
+    pub fn x(vec: Vec3) f32 {
+        return vec.v[0];
+    }
+    pub fn y(vec: Vec3) f32 {
+        return vec.v[1];
+    }
+    pub fn z(vec: Vec3) f32 {
+        return vec.v[2];
+    }
+};
+pub const Color = Vec3;
+pub const Point3 = Vec3;