diff --git a/src/renderers/shaders/ShaderChunk/common.glsl.js b/src/renderers/shaders/ShaderChunk/common.glsl.js
index ef81e9a7c918e89cdc38c374204b1be75d3b46c5..506a7b21adab6fa510f9071b1ccbf98f1c4b1469 100644
--- a/src/renderers/shaders/ShaderChunk/common.glsl.js
+++ b/src/renderers/shaders/ShaderChunk/common.glsl.js
@@ -109,5 +109,11 @@ float linearToRelativeLuminance( const in vec3 color ) {
 
 	return dot( weights, color.rgb );
 
+}
+
+bool isPerspectiveMatrix( mat4 projectionMatrix ) {
+
+  return projectionMatrix[ 2 ][ 3 ] == - 1.0;
+
 }
 `;
diff --git a/src/renderers/shaders/ShaderLib/points_vert.glsl.js b/src/renderers/shaders/ShaderLib/points_vert.glsl.js
index 58240755c75e56d9cd30587b01324ce3e911ebb4..b5bb3598f53d44d2ca4ad594a8f756eb0d7a8201 100644
--- a/src/renderers/shaders/ShaderLib/points_vert.glsl.js
+++ b/src/renderers/shaders/ShaderLib/points_vert.glsl.js
@@ -20,7 +20,7 @@ void main() {
 
 	#ifdef USE_SIZEATTENUATION
 
-		bool isPerspective = ( projectionMatrix[ 2 ][ 3 ] == - 1.0 );
+		bool isPerspective = isPerspectiveMatrix( projectionMatrix );
 
 		if ( isPerspective ) gl_PointSize *= ( scale / - mvPosition.z );
 
diff --git a/src/renderers/shaders/ShaderLib/sprite_vert.glsl.js b/src/renderers/shaders/ShaderLib/sprite_vert.glsl.js
index bffda7c897ebf2093365173d83861250d4fa4e94..604a694afeff6e5049c247fd0c1846005685358b 100644
--- a/src/renderers/shaders/ShaderLib/sprite_vert.glsl.js
+++ b/src/renderers/shaders/ShaderLib/sprite_vert.glsl.js
@@ -20,7 +20,7 @@ void main() {
 
 	#ifndef USE_SIZEATTENUATION
 
-		bool isPerspective = ( projectionMatrix[ 2 ][ 3 ] == - 1.0 );
+		bool isPerspective = isPerspectiveMatrix( projectionMatrix );
 
 		if ( isPerspective ) scale *= - mvPosition.z;