diff --git a/examples/jsm/csm/CSMFrustum.js b/examples/jsm/csm/CSMFrustum.js
index f34d26ff577428..a4b6f7507589b2 100644
--- a/examples/jsm/csm/CSMFrustum.js
+++ b/examples/jsm/csm/CSMFrustum.js
@@ -145,6 +145,9 @@ class CSMFrustum {
 
 		target.length = breaks.length;
 
+		const near = this.vertices.near[ 0 ].z;
+		const far = this.vertices.far[ 0 ].z;
+
 		for ( let i = 0; i < breaks.length; i ++ ) {
 
 			const cascade = target[ i ];
@@ -159,9 +162,11 @@ class CSMFrustum {
 
 			} else {
 
+				const alpha = ( breaks[ i - 1 ] * far - near ) / ( far - near );
+
 				for ( let j = 0; j < 4; j ++ ) {
 
-					cascade.vertices.near[ j ].lerpVectors( this.vertices.near[ j ], this.vertices.far[ j ], breaks[ i - 1 ] );
+					cascade.vertices.near[ j ].lerpVectors( this.vertices.near[ j ], this.vertices.far[ j ], alpha );
 
 				}
 
@@ -177,9 +182,11 @@ class CSMFrustum {
 
 			} else {
 
+				const alpha = ( breaks[ i ] * far - near ) / ( far - near );
+
 				for ( let j = 0; j < 4; j ++ ) {
 
-					cascade.vertices.far[ j ].lerpVectors( this.vertices.near[ j ], this.vertices.far[ j ], breaks[ i ] );
+					cascade.vertices.far[ j ].lerpVectors( this.vertices.near[ j ], this.vertices.far[ j ], alpha );
 
 				}
 
diff --git a/src/renderers/webgl-fallback/WebGLBackend.js b/src/renderers/webgl-fallback/WebGLBackend.js
index 1ef89923d982d8..707c12022bf3f4 100644
--- a/src/renderers/webgl-fallback/WebGLBackend.js
+++ b/src/renderers/webgl-fallback/WebGLBackend.js
@@ -832,6 +832,14 @@ class WebGLBackend extends Backend {
 
 				if ( setFrameBuffer && resolveRenderTarget ) this._resolveRenderTarget( descriptor );
 
+				// Restore the framebuffer of the active render pass when clearing an unrelated
+				// render target, so subsequent draws in the pass don't bind to the cleared target.
+				if ( setFrameBuffer && this._currentContext !== null && this._currentContext !== descriptor ) {
+
+					this._setFramebuffer( this._currentContext );
+
+				}
+
 			}
 
 		}