Minor improvements to AR and Clipping & Blending (#1426)

docs/ar.md

@@ -2,10 +2,11 @@
 
 ## Requirements
 
- - [ARCore](https://play.google.com/store/apps/details?id=com.google.ar.core)
+ - A mobile phone or tablet (augmented reality headsets are not supported yet)
+ - [ARCore](https://play.google.com/store/apps/details?id=com.google.ar.core) (if on Android)
  - browser with [WebXR API and immersive-ar](https://immersive-web.github.io/webxr-samples/report/) session type support
 
-At the moment of writing, only Chromium-based browsers support immersive-ar session type.
+At the moment of writing, only Chromium-based browsers on Android support immersive-ar session type.
 
 ## Other information
 
@@ -91,7 +92,7 @@ This value will not change when entering AR.
 (item [1] of [view v] matrix :: #d10000)
 ```
 
-view matrix - is a matrix that can be used to transform points from the world space (relatively to the world origin) to the view space (with origin is at the camera). It includes rotation and translation of the camera.
+view matrix - is a matrix that can be used to transform points from the view space (with origin is at the camera) to the world space (relatively to the world origin). It includes rotation and translation of the camera.
 
 Also:
 
@@ -109,7 +110,8 @@ view[15] = position[z]
 
 inverse view matrix = view matrix<sup>-1</sup>
 
-Describes the opposite transformation to the view matrix.
+Describes the opposite transformation to the view matrix: From the world space (relatively to the world origin) to the view space (with origin is at the camera).
+
 
 ---
 
@@ -186,6 +188,8 @@ screenY = y * negative_dist / z
 ```
 combined matrix = projection matrix * inverse view matrix
 
+Transforms positions from world space to view space, then to projected.
+
 ---
 
 ```scratch

extensions/ar.js

@@ -71,7 +71,7 @@
       if (!supported) {
         console.error(
           (arFail =
-            "WebXR exists in the browser you are using, but 'immersive-ar' session type is not supported")
+            "WebXR exists in the browser you are using, but 'immersive-ar' session type is not supported (it can only work on mobile)")
         );
       } else {
         arFail = null;