Made inline comments more explicit (#25575)

src/renderers/shaders/ShaderChunk/packing.glsl.js

@@ -42,21 +42,27 @@ vec2 unpackRGBATo2Half( vec4 v ) {
 	return vec2( v.x + ( v.y / 255.0 ), v.z + ( v.w / 255.0 ) );
 }
 
-// NOTE: viewZ/eyeZ is < 0 when in front of the camera per OpenGL conventions
+// NOTE: viewZ, the z-coordinate in camera space, is negative for points in front of the camera
 
 float viewZToOrthographicDepth( const in float viewZ, const in float near, const in float far ) {
+	// -near maps to 0; -far maps to 1
 	return ( viewZ + near ) / ( near - far );
 }
-float orthographicDepthToViewZ( const in float linearClipZ, const in float near, const in float far ) {
-	return linearClipZ * ( near - far ) - near;
+
+float orthographicDepthToViewZ( const in float depth, const in float near, const in float far ) {
+	// maps orthographic depth in [ 0, 1 ] to viewZ
+	return depth * ( near - far ) - near;
 }
 
 // NOTE: https://twitter.com/gonnavis/status/1377183786949959682
 
 float viewZToPerspectiveDepth( const in float viewZ, const in float near, const in float far ) {
+	// -near maps to 0; -far maps to 1
 	return ( ( near + viewZ ) * far ) / ( ( far - near ) * viewZ );
 }
-float perspectiveDepthToViewZ( const in float invClipZ, const in float near, const in float far ) {
-	return ( near * far ) / ( ( far - near ) * invClipZ - far );
+
+float perspectiveDepthToViewZ( const in float depth, const in float near, const in float far ) {
+	// maps perspective depth in [ 0, 1 ] to viewZ
+	return ( near * far ) / ( ( far - near ) * depth - far );
 }
 `;