Use linear light attenuation.

res/engine/shaders/include/Lighting.glsl

@@ -28,11 +28,8 @@ struct PointLight{
     /** Light intensity, valid values range is [0.0F; 1.0F]. */
     float intensity;
 
-    /**
-     * Distance where the light intensity is half the maximal intensity,
-     * valid values range is [0.01F; +inf].
-     */
-    float halfDistance;
+    /** Lit distance. */
+    float distance;
 
 #hlsl float2 pad1; // to pack as in Vulkan
 };
@@ -81,11 +78,8 @@ struct Spotlight{
     /** Light intensity, valid values range is [0.0F; 1.0F]. */
     float intensity;
 
-    /**
-     * Distance where the light intensity is half the maximal intensity,
-     * valid values range is [0.001F; +inf].
-     */
-    float halfDistance;
+    /** Lit distance. */
+    float distance;
 
     /**
      * Cosine of the spotlight's inner cone angle (cutoff).
@@ -188,13 +182,16 @@ vec3 calculateColorFromLightSource(
  *
  * @param distanceToLightSource Distance between pixel/fragment and the light source.
  * @param lightIntensity        Light intensity, valid values range is [0.0F; 1.0F].
- * @param lightHalfDistance     Distance where the light intensity is half the maximal intensity, valid values range is [0.001F; +inf].
+ * @param lightDistance         Lit distance.
  *
  * @return Factor in range [0.0; 1.0] where 0.0 means "no light is received" and 1.0 means "full light is received".
  */
-float calculateLightAttenuation(float distanceToLightSource, float lightIntensity, float lightHalfDistance){
-    float distanceToLightDivHalfRadius = distanceToLightSource / lightHalfDistance;
-    return lightIntensity / (1.0F + distanceToLightDivHalfRadius * distanceToLightDivHalfRadius);
+float calculateLightAttenuation(float distanceToLightSource, float lightIntensity, float lightDistance){
+    // Use linear attenuation because it allows us to do sphere/cone intersection tests in light culling
+    // more "efficient" in terms of light radius/distance to lit area. For example with linear attenuation if we have lit
+    // distance 30 almost all this distance will be somewhat lit while with "inverse squared distance" function (and similar)
+    // almost half of this distance will have pretty much no light.
+    return clamp((lightDistance - distanceToLightSource) / lightDistance, 0.0F, 1.0F) * lightIntensity;
 }
 
 /**
@@ -221,7 +218,7 @@ vec3 calculateColorFromPointLight(
     // Calculate light attenuation.
     float fragmentDistanceToLight = length(lightSource.position.xyz - fragmentPosition);
     vec3 attenuatedLightColor = lightSource.color.rgb
-        * calculateLightAttenuation(fragmentDistanceToLight, lightSource.intensity, lightSource.halfDistance);
+        * calculateLightAttenuation(fragmentDistanceToLight, lightSource.intensity, lightSource.distance);
 
     return calculateColorFromLightSource(
         attenuatedLightColor,
@@ -293,7 +290,7 @@ vec3 calculateColorFromSpotlight(
     // Calculate light attenuation.
     float fragmentDistanceToLight = length(lightSource.position.xyz - fragmentPosition);
     vec3 attenuatedLightColor = lightSource.color.rgb
-        * calculateLightAttenuation(fragmentDistanceToLight, lightSource.intensity, lightSource.halfDistance);
+        * calculateLightAttenuation(fragmentDistanceToLight, lightSource.intensity, lightSource.distance);
 
     // Calculate angle between light direction and direction from fragment to light source
     // to see if this fragment is inside of the light cone or not.

src/engine_lib/private/game/nodes/light/PointLightNode.cpp

@@ -22,7 +22,7 @@ namespace ne {
         mtxShaderData.second.shaderData.position = glm::vec4(getWorldLocation(), 1.0F);
         mtxShaderData.second.shaderData.color = glm::vec4(color, 1.0F);
         mtxShaderData.second.shaderData.intensity = intensity;
-        mtxShaderData.second.shaderData.halfDistance = halfDistance;
+        mtxShaderData.second.shaderData.distance = distance;
 #if defined(DEBUG)
         static_assert(sizeof(PointLightShaderData) == 48, "consider copying new parameters here");
 #endif
@@ -84,14 +84,11 @@ namespace ne {
         markShaderDataToBeCopiedToGpu();
     }
 
-    void PointLightNode::setLightHalfDistance(float halfDistance) {
+    void PointLightNode::setLightDistance(float distance) {
         std::scoped_lock guard(mtxShaderData.first);
 
-        // Save new parameter.
-        this->halfDistance = std::max(halfDistance, minimumHalfDistance);
-
         // Update shader data.
-        mtxShaderData.second.shaderData.halfDistance = this->halfDistance;
+        mtxShaderData.second.shaderData.distance = distance;
 
         // Mark updated shader data to be later copied to the GPU resource.
         markShaderDataToBeCopiedToGpu();
@@ -103,9 +100,6 @@ namespace ne {
         // Make sure our intensity is in range [0.0; 1.0].
         intensity = std::clamp(intensity, 0.0F, 1.0F);
 
-        // Make sure our half distance is not zero or negative.
-        halfDistance = std::max(halfDistance, minimumHalfDistance);
-
 #if defined(DEBUG)
         static_assert(sizeof(PointLightShaderData) == 48, "consider clamping new parameters here");
 #endif
@@ -135,7 +129,7 @@ namespace ne {
 
     float PointLightNode::getLightIntensity() const { return intensity; }
 
-    float PointLightNode::getLightHalfDistance() const { return halfDistance; }
+    float PointLightNode::getLightDistance() const { return distance; }
 
     void PointLightNode::onWorldLocationRotationScaleChanged() {
         SpatialNode::onWorldLocationRotationScaleChanged();

src/engine_lib/private/game/nodes/light/SpotlightNode.cpp

@@ -23,7 +23,7 @@ namespace ne {
         mtxShaderData.second.shaderData.direction = glm::vec4(getWorldForwardDirection(), 0.0F);
         mtxShaderData.second.shaderData.color = glm::vec4(color, 1.0F);
         mtxShaderData.second.shaderData.intensity = intensity;
-        mtxShaderData.second.shaderData.halfDistance = halfDistance;
+        mtxShaderData.second.shaderData.distance = distance;
         mtxShaderData.second.shaderData.cosInnerConeAngle =
             glm::cos(glm::radians(innerConeAngle / 2.0F)); // NOLINT
         mtxShaderData.second.shaderData.cosOuterConeAngle =
@@ -89,14 +89,11 @@ namespace ne {
         markShaderDataToBeCopiedToGpu();
     }
 
-    void SpotlightNode::setLightHalfDistance(float halfDistance) {
+    void SpotlightNode::setLightDistance(float distance) {
         std::scoped_lock guard(mtxShaderData.first);
 
-        // Save new parameter.
-        this->halfDistance = std::max(halfDistance, minimumHalfDistance);
-
         // Update shader data.
-        mtxShaderData.second.shaderData.halfDistance = this->halfDistance;
+        mtxShaderData.second.shaderData.distance = distance;
 
         // Mark updated shader data to be later copied to the GPU resource.
         markShaderDataToBeCopiedToGpu();
@@ -143,9 +140,6 @@ namespace ne {
         // Make sure our intensity is in range [0.0; 1.0].
         intensity = std::clamp(intensity, 0.0F, 1.0F);
 
-        // Make sure our half distance is not zero or negative.
-        halfDistance = std::max(halfDistance, minimumHalfDistance);
-
         // Make sure our cutoff angle is in range [0.0; 180.0].
         innerConeAngle = std::clamp(innerConeAngle, 0.0F, 180.0F);           // NOLINT
         outerConeAngle = std::clamp(outerConeAngle, innerConeAngle, 180.0F); // NOLINT
@@ -179,7 +173,7 @@ namespace ne {
 
     float SpotlightNode::getLightIntensity() const { return intensity; }
 
-    float SpotlightNode::getLightHalfDistance() const { return halfDistance; }
+    float SpotlightNode::getLightDistance() const { return distance; }
 
     void SpotlightNode::onWorldLocationRotationScaleChanged() {
         SpatialNode::onWorldLocationRotationScaleChanged();

src/engine_lib/public/game/nodes/light/PointLightNode.h

@@ -38,12 +38,11 @@ namespace ne RNAMESPACE() {
         void setLightIntensity(float intensity);
 
         /**
-         * Sets distance where the light intensity is half the maximum intensity (see @ref setLightIntensity).
+         * Sets lit distance (i.e. attenuation radius).
          *
-         * @param halfDistance Distance where intensity is half the maximum in range is [0.0; +inf]
-         * (will be clamped of outside of the range).
+         * @param distance Lit distance.
          */
-        void setLightHalfDistance(float halfDistance);
+        void setLightDistance(float distance);
 
         /**
          * Returns color of this light source.
@@ -60,11 +59,11 @@ namespace ne RNAMESPACE() {
         float getLightIntensity() const;
 
         /**
-         * Returns distance where the light intensity is half the maximum intensity.
+         * Returns lit distance.
          *
-         * @return Distance in range [0.0; +inf].
+         * @return Distance.
          */
-        float getLightHalfDistance() const;
+        float getLightDistance() const;
 
     protected:
         /**
@@ -124,8 +123,8 @@ namespace ne RNAMESPACE() {
             /** Light intensity. */
             alignas(iVkScalarAlignment) float intensity = 1.0F;
 
-            /** Distance where intensity is half the maximum. */
-            alignas(iVkScalarAlignment) float halfDistance = 5.0F; // NOLINT
+            /** Lit distance. */
+            alignas(iVkScalarAlignment) float distance = 1.0F;
         };
 
         /** Groups data related to shaders. */
@@ -170,15 +169,9 @@ namespace ne RNAMESPACE() {
         RPROPERTY(Serialize)
         float intensity = 1.0F;
 
-        /**
-         * Distance where the light intensity is half the maximal intensity,
-         * valid values range is [@ref minimumHalfDistance; +inf].
-         */
+        /** Lit distance. */
         RPROPERTY(Serialize)
-        float halfDistance = 5.0F; // NOLINT: seems like a pretty good default value
-
-        /** Minimum value for @ref halfDistance to avoid division by zero in shaders. */
-        static constexpr float minimumHalfDistance = 0.001F; // NOLINT
+        float distance = 10.0F; // NOLINT: seems like a pretty good default value
 
         ne_PointLightNode_GENERATED
     };

src/engine_lib/public/game/nodes/light/SpotlightNode.h

@@ -38,12 +38,11 @@ namespace ne RNAMESPACE() {
         void setLightIntensity(float intensity);
 
         /**
-         * Sets distance where the light intensity is half the maximum intensity (see @ref setLightIntensity).
+         * Sets lit distance (i.e. attenuation distance).
          *
-         * @param halfDistance Distance where intensity is half the maximum in range is [0.0; +inf]
-         * (will be clamped of outside of the range).
+         * @param distance Lit distance.
          */
-        void setLightHalfDistance(float halfDistance);
+        void setLightDistance(float distance);
 
         /**
          * Sets angle of spotlight's inner cone (cone that will have hard light edges),
@@ -78,11 +77,11 @@ namespace ne RNAMESPACE() {
         float getLightIntensity() const;
 
         /**
-         * Returns distance where the light intensity is half the maximum intensity.
+         * Returns lit distance.
          *
-         * @return Distance in range [0.0; +inf].
+         * @return Distance.
          */
-        float getLightHalfDistance() const;
+        float getLightDistance() const;
 
         /**
          * Returns light cutoff angle of the inner cone (hard light edge).
@@ -159,8 +158,8 @@ namespace ne RNAMESPACE() {
             /** Light intensity. */
             alignas(iVkScalarAlignment) float intensity = 1.0F;
 
-            /** Distance where intensity is half the maximum. */
-            alignas(iVkScalarAlignment) float halfDistance = 5.0F; // NOLINT
+            /** Lit distance. */
+            alignas(iVkScalarAlignment) float distance = 1.0F;
 
             /**
              * Cosine of the spotlight's inner cone angle (cutoff).
@@ -221,12 +220,9 @@ namespace ne RNAMESPACE() {
         RPROPERTY(Serialize)
         float intensity = 1.0F;
 
-        /**
-         * Distance where the light intensity is half the maximal intensity,
-         * valid values range is [@ref minimumHalfDistance; +inf].
-         */
+        /** Lit distance. */
         RPROPERTY(Serialize)
-        float halfDistance = 5.0F; // NOLINT: seems like a pretty good default value
+        float distance = 10.0F; // NOLINT: seems like a pretty good default value
 
         /**
          * Light cutoff angle (in degrees) of the inner cone (hard light edge).
@@ -242,9 +238,6 @@ namespace ne RNAMESPACE() {
         RPROPERTY(Serialize)
         float outerConeAngle = 120.0F;
 
-        /** Minimum value for @ref halfDistance to avoid division by zero in shaders. */
-        static constexpr float minimumHalfDistance = 0.001F; // NOLINT
-
         ne_SpotlightNode_GENERATED
     };
 }