From 3cf377c490b4a26dc96f9c96e09799bd0f257f18 Mon Sep 17 00:00:00 2001
From: robtfm <50659922+robtfm@users.noreply.github.com>
Date: Wed, 22 Nov 2023 18:54:45 +0000
Subject: [PATCH] Non uniform transmission samples (#10674)

# Objective

fix webgpu+chrome(119) textureSample in non-uniform control flow error

## Solution

modify view transmission texture sampling to use textureSampleLevel.
there are no mips for the view transmission texture, so this doesn't
change the result, but it removes the need for the samples to be in
uniform control flow.

note: in future we may add a mipchain to the transmission texture to
improve the blur effect. if uniformity analysis hasn't improved, this
would require switching to manual derivative calculations (which is
something we plan to do anyway).
---
 crates/bevy_pbr/src/render/pbr_transmission.wgsl | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_pbr/src/render/pbr_transmission.wgsl b/crates/bevy_pbr/src/render/pbr_transmission.wgsl
index 14b1e67d0d..f13e09920d 100644
--- a/crates/bevy_pbr/src/render/pbr_transmission.wgsl
+++ b/crates/bevy_pbr/src/render/pbr_transmission.wgsl
@@ -53,10 +53,11 @@ fn specular_transmissive_light(world_position: vec4<f32>, frag_coord: vec3<f32>,
 }
 
 fn fetch_transmissive_background_non_rough(offset_position: vec2<f32>, frag_coord: vec3<f32>) -> vec4<f32> {
-    var background_color = textureSample(
+    var background_color = textureSampleLevel(
         view_bindings::view_transmission_texture,
         view_bindings::view_transmission_sampler,
         offset_position,
+        0.0
     );
 
 #ifdef DEPTH_PREPASS
@@ -152,10 +153,11 @@ fn fetch_transmissive_background(offset_position: vec2<f32>, frag_coord: vec3<f3
         let modified_offset_position = offset_position + rotated_spiral_offset * blur_intensity * (1.0 - f32(pixel_checkboard) * 0.1);
 
         // Sample the view transmission texture at the offset position + noise offset, to get the background color
-        var sample = textureSample(
+        var sample = textureSampleLevel(
             view_bindings::view_transmission_texture,
             view_bindings::view_transmission_sampler,
             modified_offset_position,
+            0.0
         );
 
 #ifdef DEPTH_PREPASS