attempt to fix unaligned read in renderer

- #906

Author: mrDIMAS

fyrox-impl/src/renderer/light.rs

@@ -36,6 +36,7 @@ use crate::{
         ColorMask, CompareFunc, CullFace, DrawParameters, ElementRange, StencilAction, StencilFunc,
         StencilOp,
     },
+    include_bytes_align_as,
     renderer::{
         bundle::{LightSourceKind, RenderDataBundleStorage},
         cache::{
@@ -204,7 +205,13 @@ impl DeferredLightRenderer {
                 quality_defaults.csm_settings.precision,
             )?,
             // Use `test_write_brdf_lut` to re-generate the BRDF if needed.
-            brdf_lut: make_brdf_lut(server, 256, include_bytes!("brdf_256x256_256samples.bin"))?,
+            brdf_lut: {
+                make_brdf_lut(
+                    server,
+                    256,
+                    include_bytes_align_as!(half::f16, "brdf_256x256_256samples.bin"),
+                )?
+            },
         })
     }
 

fyrox-impl/src/renderer/utils.rs

@@ -220,6 +220,29 @@ pub fn write_brdf_lut(path: &Path, size: usize, sample_count: usize) -> std::io:
     Ok(())
 }
 
+#[repr(C)] // guarantee 'bytes' comes after '_align'
+pub(crate) struct AlignedAs<Align, Bytes: ?Sized> {
+    pub _align: [Align; 0],
+    pub bytes: Bytes,
+}
+
+// https://users.rust-lang.org/t/can-i-conveniently-compile-bytes-into-a-rust-program-with-a-specific-alignment/24049/2
+#[macro_export]
+macro_rules! include_bytes_align_as {
+    ($align_ty:ty, $path:literal) => {{
+        // const block expression to encapsulate the static
+        use $crate::renderer::utils::AlignedAs;
+
+        // this assignment is made possible by CoerceUnsized
+        static ALIGNED: &AlignedAs<$align_ty, [u8]> = &AlignedAs {
+            _align: [],
+            bytes: *include_bytes!($path),
+        };
+
+        &ALIGNED.bytes
+    }};
+}
+
 #[cfg(test)]
 mod test {
     use crate::renderer::utils::write_brdf_lut;