Merge pull request #1885 from bungoboingo/gradient-packing-optimization

Small gradient optimization

graphics/Cargo.toml

@@ -18,6 +18,7 @@ web-colors = []
 
 [dependencies]
 glam = "0.24"
+half = "2.2.1"
 log = "0.4"
 raw-window-handle = "0.5"
 thiserror = "1.0"

graphics/src/gradient.rs

@@ -7,6 +7,7 @@ use crate::color;
 use crate::core::gradient::ColorStop;
 use crate::core::{self, Color, Point, Rectangle};
 
+use half::f16;
 use std::cmp::Ordering;
 
 #[derive(Debug, Clone, PartialEq)]
@@ -99,61 +100,96 @@ impl Linear {
 
     /// Packs the [`Gradient`] for use in shader code.
     pub fn pack(&self) -> Packed {
-        let mut data: [f32; 44] = [0.0; 44];
+        let mut colors = [[0u32; 2]; 8];
+        let mut offsets = [f16::from(0u8); 8];
 
         for (index, stop) in self.stops.iter().enumerate() {
             let [r, g, b, a] =
                 color::pack(stop.map_or(Color::default(), |s| s.color))
                     .components();
 
-            data[index * 4] = r;
-            data[(index * 4) + 1] = g;
-            data[(index * 4) + 2] = b;
-            data[(index * 4) + 3] = a;
+            colors[index] = [
+                pack_f16s([f16::from_f32(r), f16::from_f32(g)]),
+                pack_f16s([f16::from_f32(b), f16::from_f32(a)]),
+            ];
 
-            data[32 + index] = stop.map_or(2.0, |s| s.offset);
+            offsets[index] =
+                stop.map_or(f16::from_f32(2.0), |s| f16::from_f32(s.offset));
         }
 
-        data[40] = self.start.x;
-        data[41] = self.start.y;
-        data[42] = self.end.x;
-        data[43] = self.end.y;
+        let offsets = [
+            pack_f16s([offsets[0], offsets[1]]),
+            pack_f16s([offsets[2], offsets[3]]),
+            pack_f16s([offsets[4], offsets[5]]),
+            pack_f16s([offsets[6], offsets[7]]),
+        ];
 
-        Packed(data)
+        let direction = [self.start.x, self.start.y, self.end.x, self.end.y];
+
+        Packed {
+            colors,
+            offsets,
+            direction,
+        }
     }
 }
 
 /// Packed [`Gradient`] data for use in shader code.
 #[derive(Debug, Copy, Clone, PartialEq)]
 #[repr(C)]
-pub struct Packed([f32; 44]);
+pub struct Packed {
+    // 8 colors, each channel = 16 bit float, 2 colors packed into 1 u32
+    colors: [[u32; 2]; 8],
+    // 8 offsets, 8x 16 bit floats packed into 4 u32s
+    offsets: [u32; 4],
+    direction: [f32; 4],
+}
 
 /// Creates a new [`Packed`] gradient for use in shader code.
 pub fn pack(gradient: &core::Gradient, bounds: Rectangle) -> Packed {
     match gradient {
         core::Gradient::Linear(linear) => {
-            let mut data: [f32; 44] = [0.0; 44];
+            let mut colors = [[0u32; 2]; 8];
+            let mut offsets = [f16::from(0u8); 8];
 
             for (index, stop) in linear.stops.iter().enumerate() {
                 let [r, g, b, a] =
                     color::pack(stop.map_or(Color::default(), |s| s.color))
                         .components();
 
-                data[index * 4] = r;
-                data[(index * 4) + 1] = g;
-                data[(index * 4) + 2] = b;
-                data[(index * 4) + 3] = a;
-                data[32 + index] = stop.map_or(2.0, |s| s.offset);
+                colors[index] = [
+                    pack_f16s([f16::from_f32(r), f16::from_f32(g)]),
+                    pack_f16s([f16::from_f32(b), f16::from_f32(a)]),
+                ];
+
+                offsets[index] = stop
+                    .map_or(f16::from_f32(2.0), |s| f16::from_f32(s.offset));
             }
 
+            let offsets = [
+                pack_f16s([offsets[0], offsets[1]]),
+                pack_f16s([offsets[2], offsets[3]]),
+                pack_f16s([offsets[4], offsets[5]]),
+                pack_f16s([offsets[6], offsets[7]]),
+            ];
+
             let (start, end) = linear.angle.to_distance(&bounds);
 
-            data[40] = start.x;
-            data[41] = start.y;
-            data[42] = end.x;
-            data[43] = end.y;
+            let direction = [start.x, start.y, end.x, end.y];
 
-            Packed(data)
+            Packed {
+                colors,
+                offsets,
+                direction,
+            }
         }
     }
 }
+
+/// Packs two f16s into one u32.
+fn pack_f16s(f: [f16; 2]) -> u32 {
+    let one = (f[0].to_bits() as u32) << 16;
+    let two = f[1].to_bits() as u32;
+
+    one | two
+}