zigrtiow: add camera class and support supersampling.

zigrtiow/src/camera.zig

@@ -0,0 +1,33 @@
+const vec = @import("./vec.zig");
+
+const Ray = @import("./ray.zig").Ray;
+
+const Point3 = vec.Point3;
+const Vec3 = vec.Vec3;
+
+pub const Camera = struct {
+    origin: Point3,
+    lower_left_corner: Point3,
+    horizontal: Vec3,
+    vertical: Vec3,
+
+    pub fn init() Camera {
+        const aspect_ratio = 16.0 / 9.0;
+        const viewport_height = 2.0;
+        const viewport_width = aspect_ratio * viewport_height;
+        const focal_length = 1.0;
+        const origin = Point3.init(0, 0, 0);
+        const horizontal = Vec3.init(viewport_width, 0.0, 0.0);
+        const vertical = Vec3.init(0.0, viewport_height, 0.0);
+
+        return Camera{
+            .origin = origin,
+            .horizontal = horizontal,
+            .vertical = vertical,
+            .lower_left_corner = origin.sub(horizontal.scale(0.5)).sub(vertical.scale(0.5)).sub(Vec3.init(0, 0, focal_length)),
+        };
+    }
+    pub fn get_ray(camera: Camera, u: f32, v: f32) Ray {
+        return Ray.init(camera.origin, camera.lower_left_corner.add(camera.horizontal.scale(u).add(camera.vertical.scale(v).sub(camera.origin))));
+    }
+};

zigrtiow/src/color.zig

@@ -1,10 +1,24 @@
 const std = @import("std");
+
+const clamp = @import("./utils.zig").clamp;
 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());
+pub fn write_color(c: Color, samples_per_pixel: isize) anyerror!void {
+    var r = c.x();
+    var g = c.y();
+    var b = c.z();
+
+    // Divide the color by the number of samples.
+    var scale = 1.0 / @intToFloat(f32, samples_per_pixel);
+    r *= scale;
+    g *= scale;
+    b *= scale;
+
+    // Write the translated [0,255] value of each color component.
+    var ir = @floatToInt(u8, 256 * clamp(r, 0, 0.999));
+    var ig = @floatToInt(u8, 256 * clamp(g, 0, 0.999));
+    var ib = @floatToInt(u8, 256 * clamp(b, 0, 0.999));
+
     const stdout = std.io.getStdOut();
     try stdout.writer().print("{d} {d} {d}\n", .{ ir, ig, ib });
 }

zigrtiow/src/main.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const camera = @import("./camera.zig");
 const color = @import("./color.zig");
 const ray = @import("./ray.zig");
 const vec = @import("./vec.zig");
@@ -6,6 +7,7 @@ const sphere = @import("./sphere.zig");
 const hittable = @import("./hittable.zig");
 const hittable_list = @import("./hittable_list.zig");
 
+const Camera = camera.Camera;
 const Color = vec.Color;
 const Hittable = hittable.Hittable;
 const HittableList = hittable_list.HittableList;
@@ -36,6 +38,7 @@ pub fn main() anyerror!void {
     const aspect_ratio: f32 = 16.0 / 9.0;
     const image_width = 400;
     const image_height = @floatToInt(isize, @intToFloat(f32, image_width) / aspect_ratio);
+    const samples_per_pixel = 100;
 
     // World
     var world = HittableList.init();
@@ -43,31 +46,32 @@ pub fn main() anyerror!void {
     try world.add(Hittable{ .sphere = Sphere.init(Point3.init(0, -100.5, -1), 100) });
 
     // Camera
-    const viewport_height = 2;
-    const viewport_width = aspect_ratio * viewport_height;
-    const focal_length = 1;
-
-    const origin = Point3.init(0, 0, 0);
-    const horizontal = Vec3.init(viewport_width, 0, 0);
-    const vertical = Vec3.init(0, viewport_height, 0);
-    const lower_left_corner = origin.sub(horizontal.scale(0.5)).sub(vertical.scale(0.5)).sub(Vec3.init(0, 0, focal_length));
+    const cam = Camera.init();
 
+    // Render
     const stdout = std.io.getStdOut();
 
     info("Writing image {d}x{d}", .{ image_width, image_height });
     try stdout.writer().print("P3\n{d} {d}\n255\n", .{ image_width, image_height });
 
+    var prng = std.rand.DefaultPrng.init(0);
+    const rand = prng.random();
     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 u = @intToFloat(f32, i) / @intToFloat(f32, image_width - 1);
-            const v = @intToFloat(f32, j) / @intToFloat(f32, image_height - 1);
-            const r = Ray.init(origin, lower_left_corner.add(horizontal.scale(u)).add(vertical.scale(v)).sub(origin));
-            const pixel_color = ray_color(r, Hittable{ .hittable_list = world });
-            try write_color(pixel_color);
+            var pixel_color = Color.init(0, 0, 0);
+            var s: isize = 0;
+            while (s < samples_per_pixel) : (s += 1) {
+                const u = (@intToFloat(f32, i) + rand.float(f32)) / @intToFloat(f32, image_width - 1);
+                const v = (@intToFloat(f32, j) + rand.float(f32)) / @intToFloat(f32, image_height - 1);
+                const r = cam.get_ray(u, v);
+                //Ray.init(origin, lower_left_corner.add(horizontal.scale(u)).add(vertical.scale(v)).sub(origin));
+                pixel_color = pixel_color.add(ray_color(r, Hittable{ .hittable_list = world }));
+            }
+            try write_color(pixel_color, samples_per_pixel);
         }
     }
     info("Done", .{});

zigrtiow/src/utils.zig

@@ -0,0 +1,5 @@
+pub fn clamp(x: f32, min: f32, max: f32) f32 {
+    if (x < min) return min;
+    if (x > max) return max;
+    return x;
+}