From 8845729351c06cd2ff1a5c1c8d24138deea624b7 Mon Sep 17 00:00:00 2001
From: Konstantin Timoshenko <rondo.devil@gmail.com>
Date: Mon, 7 Oct 2024 19:26:17 +0300
Subject: [PATCH] fix: stable reversed Z buffer implementation

Fix: reset clip state when reset is called
Fix: valid depth clear value when reversed is enabled

Feat:  non-persistent reversedZ state ( can be controlled via renderer.state.buffers.depth.setReversed(  )))
---
 src/renderers/WebGLRenderer.js           | 14 ++++++---
 src/renderers/webgl/WebGLCapabilities.js |  9 +-----
 src/renderers/webgl/WebGLState.js        | 39 ++++++++++++++++++++++--
 3 files changed, 48 insertions(+), 14 deletions(-)

diff --git a/src/renderers/WebGLRenderer.js b/src/renderers/WebGLRenderer.js
index f464e7489a516c..82ef0412214752 100644
--- a/src/renderers/WebGLRenderer.js
+++ b/src/renderers/WebGLRenderer.js
@@ -70,6 +70,7 @@ class WebGLRenderer {
 			preserveDrawingBuffer = false,
 			powerPreference = 'default',
 			failIfMajorPerformanceCaveat = false,
+			reverseDepthBuffer = false,
 		} = parameters;
 
 		this.isWebGLRenderer = true;
@@ -288,9 +289,13 @@ class WebGLRenderer {
 
 			capabilities = new WebGLCapabilities( _gl, extensions, parameters, utils );
 
-			state = new WebGLState( _gl );
+			state = new WebGLState( _gl, extensions );
 
-			if ( capabilities.reverseDepthBuffer ) state.buffers.depth.setReversed( true );
+			if ( capabilities.reverseDepthBuffer && reverseDepthBuffer ) { 
+
+				state.buffers.depth.setReversed( true );
+
+			}
 
 			info = new WebGLInfo( _gl );
 			properties = new WebGLProperties();
@@ -594,7 +599,6 @@ class WebGLRenderer {
 			if ( depth ) {
 
 				bits |= _gl.DEPTH_BUFFER_BIT;
-				_gl.clearDepth( this.capabilities.reverseDepthBuffer ? 0 : 1 );
 
 			}
 
@@ -1978,7 +1982,9 @@ class WebGLRenderer {
 
 				// common camera uniforms
 
-				if ( capabilities.reverseDepthBuffer ) {
+				const reverseDepthBuffer = state.depth.getReversed ();
+
+				if ( reverseDepthBuffer ) {
 
 					_currentProjectionMatrix.copy( camera.projectionMatrix );
 
diff --git a/src/renderers/webgl/WebGLCapabilities.js b/src/renderers/webgl/WebGLCapabilities.js
index a610a9cbbe1ea7..9fea7a1cb93c9d 100644
--- a/src/renderers/webgl/WebGLCapabilities.js
+++ b/src/renderers/webgl/WebGLCapabilities.js
@@ -92,14 +92,7 @@ function WebGLCapabilities( gl, extensions, parameters, utils ) {
 	}
 
 	const logarithmicDepthBuffer = parameters.logarithmicDepthBuffer === true;
-	const reverseDepthBuffer = parameters.reverseDepthBuffer === true && extensions.has( 'EXT_clip_control' );
-
-	if ( reverseDepthBuffer === true ) {
-
-		const ext = extensions.get( 'EXT_clip_control' );
-		ext.clipControlEXT( ext.LOWER_LEFT_EXT, ext.ZERO_TO_ONE_EXT );
-
-	}
+	const reverseDepthBuffer = extensions.has( 'EXT_clip_control' );
 
 	const maxTextures = gl.getParameter( gl.MAX_TEXTURE_IMAGE_UNITS );
 	const maxVertexTextures = gl.getParameter( gl.MAX_VERTEX_TEXTURE_IMAGE_UNITS );
diff --git a/src/renderers/webgl/WebGLState.js b/src/renderers/webgl/WebGLState.js
index 3d380b1ce69f99..cf7cb83f67bd60 100644
--- a/src/renderers/webgl/WebGLState.js
+++ b/src/renderers/webgl/WebGLState.js
@@ -14,7 +14,7 @@ const reversedFuncs = {
 	[ GreaterEqualDepth ]: LessEqualDepth,
 };
 
-function WebGLState( gl ) {
+function WebGLState( gl, extensions ) {
 
 	function ColorBuffer() {
 
@@ -88,10 +88,36 @@ function WebGLState( gl ) {
 
 			setReversed: function ( value ) {
 
+				if ( reversed !== value ) {
+
+					const ext = extensions.get( 'EXT_clip_control' );
+
+					if ( reversed ) {
+
+						ext.clipControlEXT( ext.LOWER_LEFT_EXT, ext.ZERO_TO_ONE_EXT );
+
+					} else {
+
+						ext.clipControlEXT( ext.LOWER_LEFT_EXT, ext.NEGATIVE_ONE_TO_ONE_EXT );
+
+					}
+
+					const oldDepth = currentDepthClear;
+					currentDepthClear = null;
+					this.setClear( oldDepth );
+
+				}
+
 				reversed = value;
 
 			},
 
+			getReversed: function () {
+
+				return reversed;
+
+			},
+
 			setTest: function ( depthTest ) {
 
 				if ( depthTest ) {
@@ -187,6 +213,12 @@ function WebGLState( gl ) {
 
 				if ( currentDepthClear !== depth ) {
 
+					if ( reversed ) {
+
+						depth = 1 - depth;
+
+					}
+
 					gl.clearDepth( depth );
 					currentDepthClear = depth;
 
@@ -201,7 +233,7 @@ function WebGLState( gl ) {
 				currentDepthMask = null;
 				currentDepthFunc = null;
 				currentDepthClear = null;
-
+				reversed = false;
 			}
 
 		};
@@ -1171,6 +1203,9 @@ function WebGLState( gl ) {
 
 		gl.depthMask( true );
 		gl.depthFunc( gl.LESS );
+
+		depthBuffer.setReversed ( false );
+
 		gl.clearDepth( 1 );
 
 		gl.stencilMask( 0xffffffff );