✨ Add realtime preview

- Preview quality is crude but works good enough.
- Add scaling to render function. This helps to make the preview
  faster because we can use the same result for several pixels.
- You can move around the camera a bit with wasd, super basic.
- Press R to start/stop rendering the scene.

1 files changed, 79 insertions, 0 deletions

diff --git a/racer-tracer/src/image.rs b/racer-tracer/src/image.rs
index 48e81ee..502a15a 100644
--- a/racer-tracer/src/image.rs
+++ b/racer-tracer/src/image.rs
@@ -15,3 +15,82 @@ impl Image {
         }
     }
 }
+
+// TODO: SubImage and Image can probably be the same struct
+impl From<&Image> for SubImage {
+    fn from(image: &Image) -> Self {
+        SubImage {
+            x: 0,
+            y: 0,
+            width: image.width,
+            height: image.height,
+            samples: image.samples_per_pixel,
+            screen_width: image.width,
+            screen_height: image.height,
+        }
+    }
+}
+
+pub struct SubImage {
+    pub x: usize,
+    pub y: usize,
+    pub screen_width: usize,
+    pub screen_height: usize,
+    pub width: usize,
+    pub height: usize,
+    pub samples: usize,
+}
+
+pub trait QuadSplit {
+    fn quad_split(&self) -> [SubImage; 4];
+}
+
+impl QuadSplit for SubImage {
+    fn quad_split(&self) -> [SubImage; 4] {
+        let half_w = self.width / 2;
+        let half_h = self.height / 2;
+
+        [
+            // Top Left
+            SubImage {
+                x: self.x,
+                y: self.y,
+                width: half_w,
+                height: half_h,
+                samples: self.samples,
+                screen_width: self.screen_width,
+                screen_height: self.screen_height,
+            },
+            // Top Right
+            SubImage {
+                x: self.x + half_w,
+                y: self.y,
+                width: half_w,
+                height: half_h,
+                samples: self.samples,
+                screen_width: self.screen_width,
+                screen_height: self.screen_height,
+            },
+            // Bottom Left
+            SubImage {
+                x: self.x,
+                y: self.y + half_h,
+                width: half_w,
+                height: half_h,
+                samples: self.samples,
+                screen_width: self.screen_width,
+                screen_height: self.screen_height,
+            },
+            // Bottom Right
+            SubImage {
+                x: self.x + half_w,
+                y: self.y + half_h,
+                width: half_w,
+                height: half_h,
+                samples: self.samples,
+                screen_width: self.screen_width,
+                screen_height: self.screen_height,
+            },
+        ]
+    }
+}