Improve light render parity with blender (#2549)

* improve light render parity with blender

* cleanup

* fix merge issue

* Update LightsPunctualExtensionLoader.java

* Accept changed screenshot reference images for blender light

* cleanup and parity test

* tweaks

* tweaks

* screenshots

---------

Co-authored-by: Ryan McDonough <peanut64646@gmail.com>
Co-authored-by: Richard Tingle <6330028+richardTingle@users.noreply.github.com>

Author: 3 people

jme3-core/src/main/resources/Common/ShaderLib/module/pbrlighting/PBRLightingUtils.glsllib

@@ -229,49 +229,52 @@
 
 
     #if  defined(ENABLE_PBRLightingUtils_computeDirectLightContribution) || defined(ENABLE_PBRLightingUtils_computeLightInWorldSpace)
-        void PBRLightingUtils_computeLightInWorldSpace(vec3 worldPos,vec3 worldNormal, vec3 viewDir, inout Light light){
+        void PBRLightingUtils_computeLightInWorldSpace(vec3 worldPos, vec3 worldNormal, vec3 viewDir, inout Light light){
             if(light.ready) return;
 
-            // lightComputeDir
-            float posLight = step(0.5, light.type);     
-            light.vector = light.position.xyz * sign(posLight - 0.5) - (worldPos * posLight); //tempVec lightVec
+            float posLight = step(0.5, light.type);
+            light.vector = light.position.xyz * sign(posLight - 0.5) - (worldPos * posLight);
 
-            vec3 L; // lightDir
+            vec3 L;
             float dist;
-            Math_lengthAndNormalize(light.vector,dist,L);
+            Math_lengthAndNormalize(light.vector, dist, L);
 
-            float invRange=light.invRadius; // position.w
-            const float light_threshold = 0.01;
+            if (posLight > 0.5) {
+                float clampedDist = max(dist, 0.00001);
+                float invSq = 1.0 / (clampedDist * clampedDist);
 
-            #ifdef SRGB
-                light.fallOff = (1.0 - invRange * dist) / (1.0 + invRange * dist * dist); // lightDir.w
-                light.fallOff = clamp(light.fallOff, 1.0 - posLight, 1.0);
-            #else
-                light.fallOff = clamp(1.0 - invRange * dist * posLight, 0.0, 1.0);
-            #endif
+                float radius = 1.0 / light.invRadius;
+                float rangeAtt = 1.0;
+
+                if (radius > 0.0) {
+                    float x = dist / radius;
+                    rangeAtt = clamp(1.0 - pow(x, 4.0), 0.0, 1.0);
+                }
+
+                light.fallOff = invSq * rangeAtt;
+            } else {
+                light.fallOff = 1.0;
+            }
 
-            // computeSpotFalloff
-            if(light.type>1.){
-                vec3 spotdir = normalize(light.spotDirection);
-                float curAngleCos = dot(-L, spotdir);    
+            if (light.type > 1.0) {
                 float innerAngleCos = floor(light.spotAngleCos) * 0.001;
                 float outerAngleCos = fract(light.spotAngleCos);
-                float innerMinusOuter = innerAngleCos - outerAngleCos;
-                float falloff = clamp((curAngleCos - outerAngleCos) / innerMinusOuter, 0.0, 1.0);
-                #ifdef SRGB
-                    // Use quadratic falloff (notice the ^4)
-                    falloff = pow(clamp((curAngleCos - outerAngleCos) / innerMinusOuter, 0.0, 1.0), 4.0);
-                #endif
-                light.fallOff*=falloff;
-            }
 
+                vec3 spotDir = normalize(light.spotDirection);
+                float cosA = dot(-L, spotDir);
+                float denom = max(innerAngleCos - outerAngleCos, 0.0001);
+                float spotAtten = clamp((cosA - outerAngleCos) / denom, 0.0, 1.0);
+
+                light.fallOff *= spotAtten;
+            }
 
-            vec3 h=normalize(L+viewDir);
-            light.dir=L;
+            vec3 h = normalize(L + viewDir);
+            light.dir = L;
             light.NdotL = max(dot(worldNormal, L), 0.0);
             light.NdotH = max(dot(worldNormal, h), 0.0);
             light.LdotH = max(dot(L, h), 0.0);
-            light.HdotV = max(dot(viewDir,h), 0.);
+            light.HdotV = max(dot(viewDir, h), 0.0);
+            light.ready = true;
         }
     #endif
 

jme3-effects/src/main/resources/Common/MatDefs/Post/KHRToneMap.frag

@@ -18,13 +18,13 @@ uniform sampler2DMS m_Texture;
 
 vec4 applyToneMap() {
     ivec2 iTexC = ivec2(texCoord * vec2(textureSize(m_Texture)));
-    vec4 color = vec4(0.0);
+    vec4 hdrColor = vec4(0.0);
     for (int i = 0; i < NUM_SAMPLES; i++) {
-        vec4 hdrColor = texelFetch(m_Texture, iTexC, i);
-        vec3 ldrColor = applyCurve(hdrColor.rgb);
-        color += vec4(ldrColor, hdrColor.a);
+        hdrColor += texelFetch(m_Texture, iTexC, i);
     }
-    return color / float(NUM_SAMPLES);
+    hdrColor /= float(NUM_SAMPLES);
+    vec3 ldrColor = vec4(applyCurve(hdrColor.rgb), hdrColor.a);
+    return ldrColor;
 }
 
 #else

jme3-examples/src/main/java/jme3test/light/TestLightImportParity.java

@@ -0,0 +1,55 @@
+package jme3test.light;
+
+import com.jme3.app.SimpleApplication;
+import com.jme3.environment.EnvironmentProbeControl;
+import com.jme3.input.ChaseCamera;
+import com.jme3.math.FastMath;
+import com.jme3.math.Quaternion;
+import com.jme3.math.Vector3f;
+import com.jme3.post.FilterPostProcessor;
+import com.jme3.post.filters.KHRToneMapFilter;
+import com.jme3.scene.Node;
+import com.jme3.scene.Spatial;
+import com.jme3.util.SkyFactory;
+
+/**
+ * Test how lights render compared to the same scene in Blender. Open
+ * jme3-testdata/src/main/resources/BlenderParity/scene.blend in blender to compare.
+ */
+public class TestLightImportParity extends SimpleApplication {
+    public static void main(String[] args) {
+        TestLightImportParity app = new TestLightImportParity();
+        app.start();
+    }
+
+    @Override
+    public void simpleInitApp() {
+
+        flyCam.setDragToRotate(true);
+        flyCam.setMoveSpeed(100f);
+        
+        Spatial sky = SkyFactory.createSky(assetManager, "Textures/Sky/Alien.png", SkyFactory.EnvMapType.EquirectMap);
+        sky.rotate(new Quaternion().fromAngleAxis(FastMath.PI, Vector3f.UNIT_Y));
+        rootNode.attachChild(sky);
+
+        EnvironmentProbeControl probe = new EnvironmentProbeControl(assetManager, 512);
+        rootNode.addControl(probe);
+        probe.tag(sky);
+        
+        Node scene = (Node)assetManager.loadModel("BlenderParity/scene.glb");
+        rootNode.attachChild(scene);
+
+        KHRToneMapFilter toneMap = new KHRToneMapFilter();
+        FilterPostProcessor fpp = new FilterPostProcessor(assetManager);
+        fpp.addFilter(toneMap);
+        viewPort.addProcessor(fpp);
+
+        ChaseCamera chaseCam = new ChaseCamera(cam, scene, inputManager);
+        chaseCam.setDefaultDistance(100);
+        chaseCam.setMaxDistance(200);
+        
+        
+
+         
+    }
+}

jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfUtils.java

@@ -795,7 +795,10 @@ public static ColorRGBA getAsColor(JsonObject parent, String name) {
             return null;
         }
         JsonArray color = el.getAsJsonArray();
-        return new ColorRGBA(color.get(0).getAsFloat(), color.get(1).getAsFloat(), color.get(2).getAsFloat(), color.size() > 3 ? color.get(3).getAsFloat() : 1f);
+        // glTF colors are authored in linear space unless the spec says otherwise.
+        return new ColorRGBA().set(
+            color.get(0).getAsFloat(), color.get(1).getAsFloat(), color.get(2).getAsFloat(), color.size() > 3 ? color.get(3).getAsFloat() : 1f
+        );
     }
 
     public static ColorRGBA getAsColor(JsonObject parent, String name, ColorRGBA defaultValue) {

jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/LightsPunctualExtensionLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2024 jMonkeyEngine
+ * Copyright (c) 2009-2026 jMonkeyEngine
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -53,9 +53,11 @@
  *
  * Supports directional, point, and spot lights.
  *
- * Created by Trevor Flynn - 3/23/2021
+ * @author Trevor Flynn, Riccardo Balbo
  */
 public class LightsPunctualExtensionLoader implements ExtensionLoader {
+    private static final boolean COMPUTE_LIGHT_RANGE = true;
+    private static final float GLTF_LIGHT_COMPAT_SCALE = 0.0009f;
 
     private final HashSet<NodeNeedingLight> pendingNodes = new HashSet<>();
     private final HashMap<Integer, Light> lightDefinitions = new HashMap<>();
@@ -126,13 +128,11 @@ private SpotLight buildSpotLight(JsonObject obj) {
 
         float intensity = obj.has("intensity") ? obj.get("intensity").getAsFloat() : 1.0f;
         ColorRGBA color = obj.has("color") ? GltfUtils.getAsColor(obj, "color") : new ColorRGBA(ColorRGBA.White);
-        color = lumensToColor(color, intensity);
-        float range = obj.has("range") ? obj.get("range").getAsFloat() : Float.POSITIVE_INFINITY;
 
         //Spot specific
         JsonObject spot = obj.getAsJsonObject("spot");
-        float innerConeAngle = spot != null && spot.has("innerConeAngle") ? spot.get("innerConeAngle").getAsFloat() : 0f;
-        float outerConeAngle = spot != null && spot.has("outerConeAngle") ? spot.get("outerConeAngle").getAsFloat() : ((float) Math.PI) / 4f;
+        float innerConeAngle = (spot != null && spot.has("innerConeAngle")) ? spot.get("innerConeAngle").getAsFloat() : 0f;
+        float outerConeAngle = (spot != null && spot.has("outerConeAngle"))? spot.get("outerConeAngle").getAsFloat() : (FastMath.PI / 4f);
 
         /*
         Correct floating point error on half PI, GLTF spec says that the outerConeAngle
@@ -143,9 +143,12 @@ private SpotLight buildSpotLight(JsonObject obj) {
             outerConeAngle = FastMath.HALF_PI - 0.000001f;
         }
 
+        float scaledIntensity = toCompatIntensity(intensity);
+
+        float range = obj.has("range") ? obj.get("range").getAsFloat() : (COMPUTE_LIGHT_RANGE ? getCutoffDistance(color, scaledIntensity) : Float.POSITIVE_INFINITY);
         SpotLight spotLight = new SpotLight(true);
         spotLight.setName(name);
-        spotLight.setColor(color);
+        spotLight.setColor(applyScaledIntensity(color, scaledIntensity));
         spotLight.setSpotRange(range);
         spotLight.setSpotInnerAngle(innerConeAngle);
         spotLight.setSpotOuterAngle(outerConeAngle);
@@ -165,11 +168,11 @@ private DirectionalLight buildDirectionalLight(JsonObject obj) {
 
         float intensity = obj.has("intensity") ? obj.get("intensity").getAsFloat() : 1.0f;
         ColorRGBA color = obj.has("color") ? GltfUtils.getAsColor(obj, "color") : new ColorRGBA(ColorRGBA.White);
-        color = lumensToColor(color, intensity);
+        float scaledIntensity = toCompatIntensity(intensity);
 
         DirectionalLight directionalLight = new DirectionalLight(true);
         directionalLight.setName(name);
-        directionalLight.setColor(color);
+        directionalLight.setColor(applyScaledIntensity(color, scaledIntensity));
         directionalLight.setDirection(Vector3f.UNIT_Z.negate());
 
         return directionalLight;
@@ -185,13 +188,16 @@ private PointLight buildPointLight(JsonObject obj) {
         String name = obj.has("name") ? obj.get("name").getAsString() : "";
 
         float intensity = obj.has("intensity") ? obj.get("intensity").getAsFloat() : 1.0f;
-        ColorRGBA color = obj.has("color") ? GltfUtils.getAsColor(obj, "color") : new ColorRGBA(ColorRGBA.White);
-        color = lumensToColor(color, intensity);
-        float range = obj.has("range") ? obj.get("range").getAsFloat() : Float.POSITIVE_INFINITY;
+        ColorRGBA color = obj.has("color") ? GltfUtils.getAsColor(obj, "color")
+                                           : new ColorRGBA(ColorRGBA.White);
+        
+        float scaledIntensity = toCompatIntensity(intensity);
+
+        float range = obj.has("range") ? obj.get("range").getAsFloat() : (COMPUTE_LIGHT_RANGE ? getCutoffDistance(color, scaledIntensity) : Float.POSITIVE_INFINITY);
 
         PointLight pointLight = new PointLight(true);
         pointLight.setName(name);
-        pointLight.setColor(color);
+        pointLight.setColor(applyScaledIntensity(color, scaledIntensity));
         pointLight.setRadius(range);
 
         return pointLight;
@@ -206,7 +212,7 @@ private PointLight buildPointLight(JsonObject obj) {
      */
     private void addLight(Node parent, Node node, int lightIndex) {
         if (lightDefinitions.containsKey(lightIndex)) {
-            Light light = lightDefinitions.get(lightIndex);
+            Light light = lightDefinitions.get(lightIndex).clone();
             parent.addLight(light);
             LightControl control = new LightControl(light);
             control.setInvertAxisDirection(true);
@@ -216,55 +222,17 @@ private void addLight(Node parent, Node node, int lightIndex) {
         }
     }
 
-    /**
-     * Convert a floating point lumens value into a color that
-     * represents both color and brightness of the light.
-     *
-     * @param color The base color of the light
-     * @param lumens The lumens value to convert to a color
-     * @return A color representing the intensity of the given lumens encoded into the given color
-     */
-    private ColorRGBA lumensToColor(ColorRGBA color, float lumens) {
-        ColorRGBA brightnessModifier = lumensToColor(lumens);
-        return color.mult(brightnessModifier);
+    private float toCompatIntensity(float intensity) {
+        return intensity * GLTF_LIGHT_COMPAT_SCALE;
     }
 
-    /**
-     * Convert a floating point lumens value into a grayscale color that
-     * represents a brightness.
-     *
-     * @param lumens The lumens value to convert to a color
-     * @return A color representing the intensity of the given lumens
-     */
-    private ColorRGBA lumensToColor(float lumens) {
-        /*
-        Taken from /Common/ShaderLib/Hdr.glsllib
-        vec4 HDR_EncodeLum(in float lum){
-        float Le = 2.0 * log2(lum + epsilon) + 127.0;
-        vec4 result = vec4(0.0);
-        result.a = fract(Le);
-        result.rgb = vec3((Le - (floor(result.a * 255.0)) / 255.0) / 255.0);
-        return result;
-         */
-        float epsilon = 0.0001f;
-
-        double Le = 2f * Math.log(lumens * epsilon) / Math.log(2) + 127.0;
-        ColorRGBA color = new ColorRGBA();
-        color.a = (float) (Le - Math.floor(Le)); //Get fractional part
-        float val = (float) ((Le - (Math.floor(color.a * 255.0)) / 255.0) / 255.0);
-        color.r = val;
-        color.g = val;
-        color.b = val;
-
-        return color;
+    private ColorRGBA applyScaledIntensity(ColorRGBA color, float scaledIntensity) {
+        return color.mult(scaledIntensity);
     }
 
-    /**
-     * A bean to contain the relation between a node and a light index
-     */
     private static class NodeNeedingLight {
-        private Node node;
-        private int lightIndex;
+        private final Node node;
+        private final int lightIndex;
 
         private NodeNeedingLight(Node node, int lightIndex) {
             this.node = node;
@@ -275,16 +243,35 @@ private Node getNode() {
             return node;
         }
 
-        private void setNode(Node node) {
-            this.node = node;
-        }
-
         private int getLightIndex() {
             return lightIndex;
         }
+    }
+    /**
+     * Computes the effective cutoff distance of a light based on its raw color and intensity. Uses
+     * inverse-square attenuation and a perceptual visibility threshold.
+     *
+     * @param color
+     *            The base RGB color of the light (linear space)
+     * @param intensity
+     *            The light's intensity in lumens (or equivalent)
+     * @return The cutoff distance where the light falls below a visible threshold
+     */
+    private float getCutoffDistance(ColorRGBA color, float scaledIntensity) {
+        final float visibleThreshold = 0.001f;
+        final float maxRange = 10000f;
 
-        private void setLightIndex(int lightIndex) {
-            this.lightIndex = lightIndex;
+        // Compute the max channel (R/G/B) for luminance estimation
+        float maxComponent = Math.max(Math.max(color.r, color.g), color.b);
+
+        if (maxComponent <= 0f || scaledIntensity <= 0f) {
+            return 0f;
         }
+
+        // The actual light output (lux at 1 meter) per component
+        float effectiveIntensity = maxComponent * scaledIntensity;
+        // Inverse-square attenuation: intensity / d^2 = visibleThreshold
+        float range = (float) Math.sqrt(effectiveIntensity / visibleThreshold);
+        return Math.min(range, maxRange);
     }
-}
+}