From b9419390955fe4165bcd81105b63a7e5ca0c1f60 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E2=80=94?= <drcmda@gmail.com>
Date: Sun, 27 Nov 2022 11:42:13 +0100
Subject: [PATCH] feat: hud

---
 README.md         | 39 +++++++++++++++++++++++++++++++++++++
 src/core/Hud.tsx  | 49 +++++++++++++++++++++++++++++++++++++++++++++++
 src/core/index.ts |  1 +
 3 files changed, 89 insertions(+)
 create mode 100644 src/core/Hud.tsx

diff --git a/README.md b/README.md
index bffe351b3..d47c4f99c 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,7 @@ The `native` route of the library **does not** export `Html` or `Loader`. The de
         </ul>
         <li><a href="#portals">Portals</a></li>        
         <ul>
+          <li><a href="#hud">Hud</a></li>
           <li><a href="#view">View</a></li>
           <li><a href="#rendertexture">RenderTexture</a></li>
           <li><a href="#mask">Mask</a></li>
@@ -2341,6 +2342,44 @@ function Effects() {
 
 # Portals
 
+#### Hud
+
+<p>
+  <a href="https://codesandbox.io/s/py4db"><img width="20%" src="https://codesandbox.io/api/v1/sandboxes/py4db/screenshot.png" alt="Demo"/></a>
+</p>
+
+Renders a heads-up-display (HUD). Each HUD is a scene on top of the previous. That scene is inside a React `createPortal` and is completely isolated, you can have your own cameras in there, environments, etc. The first HUD (`renderpriotity === 1`) will clear the scene and render the default scene, it needs to be the first to execute! Make sure to be explicit about the `renderpriority` of your HUDs.
+
+```tsx
+type HudProps = {
+  /** Any React node */
+  children: React.ReactNode
+  /** Render priority, default: 1 */
+  renderPriority?: number
+}
+```
+
+```jsx
+{
+  /* Renders on top of the default scene with a perspective camera */
+}
+;<Hud>
+  <PerspectiveCamera makeDefault position={[0, 0, 10]} />
+  <mesh>
+    <ringGeometry />
+  </mesh>
+</Hud>
+{
+  /* Renders on top of the previous HUD with an orthographic camera */
+}
+;<Hud renderPriority={2}>
+  <OrthographicCamera makeDefault position={[0, 0, 10]} />
+  <mesh>
+    <boxGeometry />
+  </mesh>
+</Hud>
+```
+
 #### View
 
 <p>
diff --git a/src/core/Hud.tsx b/src/core/Hud.tsx
new file mode 100644
index 000000000..4ecbcbb85
--- /dev/null
+++ b/src/core/Hud.tsx
@@ -0,0 +1,49 @@
+import * as THREE from 'three'
+import * as React from 'react'
+import { useFrame, useThree, createPortal } from '@react-three/fiber'
+
+type RenderHudProps = {
+  defaultScene: THREE.Scene
+  defaultCamera: THREE.Camera
+  renderPriority?: number
+}
+
+type HudProps = {
+  /** Any React node */
+  children: React.ReactNode
+  /** Render priority, default: 1 */
+  renderPriority?: number
+}
+
+function RenderHud({ defaultScene, defaultCamera, renderPriority = 1 }: RenderHudProps) {
+  const { gl, scene, camera } = useThree()
+  useFrame(() => {
+    if (renderPriority === 1) {
+      // Clear scene and render the default scene
+      gl.autoClear = true
+      gl.render(defaultScene, defaultCamera)
+    }
+    // Disable cleaning and render the portal with its own camera
+    gl.autoClear = false
+    gl.clearDepth()
+    gl.render(scene, camera)
+  }, renderPriority)
+  return <> </>
+}
+
+export function Hud({ children, renderPriority = 1 }: HudProps) {
+  const { scene: defaultScene, camera: defaultCamera } = useThree()
+  const [hudScene] = React.useState(() => new THREE.Scene())
+  return (
+    <>
+      {createPortal(
+        <>
+          {children}
+          <RenderHud defaultScene={defaultScene} defaultCamera={defaultCamera} renderPriority={renderPriority} />
+        </>,
+        hudScene,
+        { events: { priority: renderPriority + 1 } }
+      )}
+    </>
+  )
+}
diff --git a/src/core/index.ts b/src/core/index.ts
index 328673509..e52700f9e 100644
--- a/src/core/index.ts
+++ b/src/core/index.ts
@@ -118,3 +118,4 @@ export * from './PerformanceMonitor'
 // Portals
 export * from './RenderTexture'
 export * from './Mask'
+export * from './Hud'