Improve description of light intensity and power units. (#22299)

docs/api/en/lights/Light.html

@@ -41,8 +41,7 @@
 		<h3>[property:Float intensity]</h3>
 		<p>
 			The light's intensity, or strength.<br />
-			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, the product of
-			[page:.color color] * intensity is interpreted as luminous intensity measured in candela.<br />
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, the units of intensity depend on the type of light.<br />
 			Default - *1.0*.
 		</p>
 

docs/api/en/lights/PointLight.html

@@ -77,17 +77,23 @@ scene.add( light );
 			Default is *0.0*.
 		</p>
 
+		<h3>[property:Float intensity]</h3>
+		<p>
+			The light's intensity. Default is *1*. <br />
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, intensity is the luminous
+			intensity of the light measured in candela (cd).<br /><br />
+
+			Changing the intensity will also change the light's power.
+
+		</p>
+
 		<h3>[property:Float power]</h3>
 		<p>
 			The light's power.<br />
-			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, the luminous
-			power of the light measured in lumens. Default is *4Math.PI*. <br /><br />
-
-			This is directly related to the [page:.intensity intensity] in the ratio
-			<code>
-				power = intensity * 4&pi;
-			</code>
-			and changing this will also change the intensity.
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, power is the luminous
+			power of the light measured in lumens (lm). <br /><br />
+
+			Changing the power will also change the light's intensity.
 		</p>
 
 		<h3>[property:PointLightShadow shadow]</h3>

docs/api/en/lights/RectAreaLight.html

@@ -62,6 +62,25 @@ rectLight.add( rectLightHelper );
 			See the base [page:Light Light] class for common properties.
 		</p>
 
+		<h3>[property:Float intensity]</h3>
+		<p>
+			The light's intensity. Default is *1*. <br />
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, intensity is the luminance
+			(brightness) of the light measured in nits (cd/m^2).<br /><br />
+
+			Changing the intensity will also change the light's power.
+
+		</p>
+
+		<h3>[property:Float power]</h3>
+		<p>
+			The light's power.<br />
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, power is the luminous
+			power of the light measured in lumens (lm). <br /><br />
+
+			Changing the power will also change the light's intensity.
+		</p>
+
 		<h2>Methods</h2>
 		<p>
 			See the base [page:Light Light] class for common methods.

docs/api/en/lights/SpotLight.html

@@ -103,6 +103,16 @@
 			Default is *0.0*.
 		</p>
 
+		<h3>[property:Float intensity]</h3>
+		<p>
+			The light's intensity. Default is *1*. <br />
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, intensity is the luminous
+			intensity of the light measured in candela (cd).<br /><br />
+
+			Changing the power will also change the light's intensity.
+
+		</p>
+
 		<h3>[property:Float penumbra]</h3>
 		<p>
 			Percent of the spotlight cone that is attenuated due to penumbra. Takes values between
@@ -117,16 +127,13 @@
 		<h3>[property:Float power]</h3>
 		<p>
 			The light's power.<br />
-			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, the luminous
-			power of the light measured in lumens. Default is *4Math.PI*. <br /><br />
+			In [page:WebGLRenderer.physicallyCorrectLights physically correct] mode, power is the luminous
+			power of the light measured in lumens (lm). <br /><br />
 
-			This is directly related to the [page:.intensity intensity] in the ratio
-			<code>
-				power = intensity * &pi;
-			</code>
-			and changing this will also change the intensity.
+			Changing this will also change the light's intensity.
 		</p>
 
+
 		<h3>[property:SpotLightShadow shadow]</h3>
 		<p>
 			A [page:SpotLightShadow] used to calculate shadows for this light.