From 63cee9aa6eb62afb2e8e726d2de16b76935c5f4c Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Mon, 24 Jun 2024 16:22:20 +0100
Subject: Refactor camera

---
 Makefile  |  6 +++---
 camera.go | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 rtiaw.go  | 45 ++------------------------------------------
 3 files changed, 69 insertions(+), 46 deletions(-)
 create mode 100644 camera.go

diff --git a/Makefile b/Makefile
index 7bcf3da..7a62fa2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,9 @@
-rtiaw: $(wildcard *.go)
-	go build
-
 out.ppm : rtiaw
 	./$< > $@
 
+rtiaw: $(wildcard *.go)
+	go build
+
 .phony: view clean
 
 view: out.ppm
diff --git a/camera.go b/camera.go
new file mode 100644
index 0000000..e460cc0
--- /dev/null
+++ b/camera.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+  "fmt"
+  "os"
+)
+
+type Camera struct {
+  ImageWidth uint
+  ImageHeight uint
+  Centre Vec3
+  PDU Vec3
+  PDV Vec3
+  Pixel00 Vec3
+}
+
+func NewCamera(w uint, ar float64) (cam Camera) {
+  cam.ImageWidth = w;
+  cam.ImageHeight = uint(float64(cam.ImageWidth) / ar);
+  if cam.ImageHeight < 1 {
+    cam.ImageHeight = 1;
+  }
+
+  focal_length := 1.0;
+  viewport_height := 2.0;
+  viewport_width := viewport_height *
+                       float64(cam.ImageWidth) /
+                       float64(cam.ImageHeight);
+  cam.Centre = Splat(0);
+
+  viewport_u := Vec3{viewport_width, 0, 0};
+  viewport_v := Vec3{0, -viewport_height, 0};
+
+  cam.PDU = viewport_u.Div(Splat(float64(cam.ImageWidth)));
+  cam.PDV = viewport_v.Div(Splat(float64(cam.ImageHeight)));
+
+  viewport_upperleft := cam.Centre.
+                        Sub(Vec3{0, 0, focal_length}).
+                        Sub(viewport_u.Div(Splat(2))).
+                        Sub(viewport_v.Div(Splat(2)));
+  cam.Pixel00 = viewport_upperleft.
+                 Add(cam.PDU.Add(cam.PDV).Div(Splat(2)));
+
+  return;
+}
+
+func (cam Camera) Render(world Hittable) {
+  fmt.Printf("P3\n%d %d\n255\n", cam.ImageWidth, cam.ImageHeight);
+  for row := uint(0); row < cam.ImageHeight; row++ {
+    fmt.Fprintf(os.Stderr,
+                "Scanlines remaining: %3d...",
+                (cam.ImageHeight - row));
+    for col := uint(0); col < cam.ImageWidth; col++ {
+      pixel_centre := cam.Pixel00.
+                      Add(cam.PDU.Mul(Splat(float64(col)))).
+                      Add(cam.PDV.Mul(Splat(float64(row))));
+      ray_direction := pixel_centre.Sub(cam.Centre);
+      ray := Ray{cam.Centre, ray_direction}
+      pixel_colour := ray.Colour(world);
+      fmt.Printf("%s    ", pixel_colour.ToPPM());
+    }
+    fmt.Printf("\n");
+  }
+}
diff --git a/rtiaw.go b/rtiaw.go
index 9f900b6..03cee09 100644
--- a/rtiaw.go
+++ b/rtiaw.go
@@ -9,53 +9,12 @@ import (
 func main() {
   start := time.Now();
 
-  image_width := 400;
-  aspect := 16.0 / 9.0;
-
   var world Hittables;
   world.Add(Sphere{Vec3{0,    0  , -1},   0.5});
   world.Add(Sphere{Vec3{0, -100.5, -1}, 100  });
 
-  image_height := int(float64(image_width) / aspect);
-  if image_height < 1 {
-    image_height = 1;
-  }
-
-  focal_length := 1.0;
-  viewport_height := 2.0;
-  viewport_width := viewport_height *
-                      (float64(image_width) / float64(image_height));
-  camera_centre := Splat(0);
-
-  viewport_u := Vec3{viewport_width, 0, 0};
-  viewport_v := Vec3{0, -viewport_height, 0};
-
-  pd_u := viewport_u.Div(Splat(float64(image_width)));
-  pd_v := viewport_v.Div(Splat(float64(image_height)));
-
-  viewport_upperleft := camera_centre.
-                        Sub(Vec3{0, 0, focal_length}).
-                        Sub(viewport_u.Div(Splat(2))).
-                        Sub(viewport_v.Div(Splat(2)));
-  pixel00_loc := viewport_upperleft.
-                 Add(pd_u.Add(pd_v).Div(Splat(2)));
-
-  fmt.Printf("P3\n%d %d\n255\n", image_width, image_height);
-  for row := 0; row < image_height; row++ {
-    fmt.Fprintf(os.Stderr,
-                "Scanlines remaining: %3d...",
-                (image_height - row));
-    for col := 0; col < image_width; col++ {
-      pixel_centre := pixel00_loc.
-                      Add(pd_u.Mul(Splat(float64(col)))).
-                      Add(pd_v.Mul(Splat(float64(row))));
-      ray_direction := pixel_centre.Sub(camera_centre);
-      ray := Ray{camera_centre, ray_direction}
-      pixel_colour := ray.Colour(world);
-      fmt.Printf("%s    ", pixel_colour.ToPPM());
-    }
-    fmt.Printf("\n");
-  }
+  cam := NewCamera(400, 16.0/9.0);
+  cam.Render(world);
 
   dur := time.Since(start);
   fmt.Fprintf(os.Stderr,
-- 
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