Improve punctual shadow resolution rescale algorithm 2

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -71,6 +71,7 @@ The version number for this package has increased due to a version update of a r
 - Standardized naming for the option regarding Transparent objects being able to receive Screen Space Reflections.
 - Making the reflection and refractions of cubemaps distance based.
 - Changed Receive SSR to also controls Receive SSGI on opaque objects.
+- Improved the punctual light shadow rescale algorithm.
 
 ## [10.1.0] - 2020-10-12
 

com.unity.render-pipelines.high-definition/Runtime/Lighting/Light/HDAdditionalLightData.cs

@@ -1979,7 +1979,7 @@ internal int GetResolutionFromSettings(ShadowMapType shadowMapType, HDShadowInit
             }
         }
 
-        internal void ReserveShadowMap(Camera camera, HDShadowManager shadowManager, HDShadowSettings shadowSettings, HDShadowInitParameters initParameters, Rect screenRect, HDLightType lightType)
+        internal void ReserveShadowMap(Camera camera, HDShadowManager shadowManager, HDShadowSettings shadowSettings, HDShadowInitParameters initParameters, VisibleLight visibleLight, HDLightType lightType)
         {
             if (!m_WillRenderShadowMap)
                 return;
@@ -2013,14 +2013,26 @@ internal void ReserveShadowMap(Camera camera, HDShadowManager shadowManager, HDS
 
             if (viewPortRescaling && !shadowIsInCacheSystem)
             {
-                // resize viewport size by the normalized size of the light on screen
-                float screenArea = screenRect.width * screenRect.height;
-                viewportSize *= Mathf.Lerp(64f / viewportSize.x, 1f, screenArea);
-                viewportSize = Vector2.Max(new Vector2(64f, 64f) / viewportSize, viewportSize);
+                // Formulas: https://www.desmos.com/calculator/tdodbuysut f(x) is the distance between 0 and 1, g(x) is the screen ratio (oscillating to simulate different light sizes)
+                // The idea is to have a lot of resolution when the camera is close to the light OR the screen area is high.
+
+                // linear normalized distance between the light and camera with max shadow distance
+                float distance01 = Mathf.Clamp01(Vector3.Distance(camera.transform.position, visibleLight.GetPosition()) / shadowSettings.maxShadowDistance.value);
+                // ease out and invert the curve, give more importance to closer distances
+                distance01 = 1.0f - Mathf.Pow(distance01, 2);
+
+                // normalized ratio between light range and distance 
+                float range01 = Mathf.Clamp01(visibleLight.range / Vector3.Distance(camera.transform.position, visibleLight.GetPosition()));
 
-                // Prevent flickering caused by the floating size of the viewport
-                viewportSize.x = Mathf.Round(viewportSize.x);
-                viewportSize.y = Mathf.Round(viewportSize.y);
+                float scaleFactor01 = Mathf.Max(distance01, range01);
+
+                // We allow a maximum of 64 rescale between the highest and lowest shadow resolution
+                // It prevent having too many resolution changes when the player is moving.
+                const float maxRescaleSteps = 64;
+                scaleFactor01 = Mathf.RoundToInt(scaleFactor01 * maxRescaleSteps) / maxRescaleSteps;
+
+                // resize viewport size by the normalized size of the light on screen
+                viewportSize = Vector2.Lerp(HDShadowManager.k_MinShadowMapResolution * Vector2.one, viewportSize, scaleFactor01);
             }
 
             viewportSize = Vector2.Max(viewportSize, new Vector2(HDShadowManager.k_MinShadowMapResolution, HDShadowManager.k_MinShadowMapResolution));

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/LightLoop.cs

@@ -2363,7 +2363,7 @@ int PreprocessVisibleLights(HDCamera hdCamera, CullingResults cullResults, Debug
                 // Reserve shadow map resolutions and check if light needs to render shadows
                 if (additionalData.WillRenderShadowMap())
                 {
-                    additionalData.ReserveShadowMap(hdCamera.camera, m_ShadowManager, hdShadowSettings, m_ShadowInitParameters, light.screenRect, lightType);
+                    additionalData.ReserveShadowMap(hdCamera.camera, m_ShadowManager, hdShadowSettings, m_ShadowInitParameters, light, lightType);
                 }
 
                 // Reserve the cookie resolution in the 2D atlas