From bf7948f4d24bf64c0b15dd05c78aafcd09abb51b Mon Sep 17 00:00:00 2001
From: Kai Ninomiya <kainino@chromium.org>
Date: Wed, 29 May 2024 09:47:59 -0700
Subject: [PATCH] Fix orientation of cubemap sample, add clearer attribution
 (#419)

---
 public/assets/img/cubemap/credit.txt   | 1 +
 sample/cubemap/meta.ts                 | 2 +-
 sample/cubemap/sampleCubemap.frag.wgsl | 8 ++++++--
 3 files changed, 8 insertions(+), 3 deletions(-)
 create mode 100644 public/assets/img/cubemap/credit.txt

diff --git a/public/assets/img/cubemap/credit.txt b/public/assets/img/cubemap/credit.txt
new file mode 100644
index 00000000..de98f1c6
--- /dev/null
+++ b/public/assets/img/cubemap/credit.txt
@@ -0,0 +1 @@
+Cubemap image available under a Creative Commons Attribution 3.0 Unported License at https://www.humus.name/index.php?page=Textures&ID=58
diff --git a/sample/cubemap/meta.ts b/sample/cubemap/meta.ts
index 91f5b56a..ab2dcdda 100644
--- a/sample/cubemap/meta.ts
+++ b/sample/cubemap/meta.ts
@@ -1,7 +1,7 @@
 export default {
   name: 'Cubemap',
   description:
-    'This example shows how to render and sample from a cubemap texture.',
+    'This example shows how to render and sample from a cubemap texture. Cubemap image available under a Creative Commons Attribution 3.0 Unported License at https://www.humus.name/index.php?page=Textures&ID=58',
   filename: __DIRNAME__,
   sources: [
     { path: 'main.ts' },
diff --git a/sample/cubemap/sampleCubemap.frag.wgsl b/sample/cubemap/sampleCubemap.frag.wgsl
index 757b42d0..1e04597c 100644
--- a/sample/cubemap/sampleCubemap.frag.wgsl
+++ b/sample/cubemap/sampleCubemap.frag.wgsl
@@ -7,8 +7,12 @@ fn main(
   @location(1) fragPosition: vec4f
 ) -> @location(0) vec4f {
   // Our camera and the skybox cube are both centered at (0, 0, 0)
-  // so we can use the cube geomtry position to get viewing vector to sample the cube texture.
-  // The magnitude of the vector doesn't matter.
+  // so we can use the cube geometry position to get viewing vector to sample
+  // the cube texture. The magnitude of the vector doesn't matter.
   var cubemapVec = fragPosition.xyz - vec3(0.5);
+  // When viewed from the inside, cubemaps are left-handed (z away from viewer),
+  // but common camera matrix convention results in a right-handed world space
+  // (z toward viewer), so we have to flip it.
+  cubemapVec.z *= -1;
   return textureSample(myTexture, mySampler, cubemapVec);
 }