Add workaround to make the preview more responsive when using ray bra…

…nching (chunky-dev#1620) * Workaround for some potential drawbacks of ray branching * split getBranchCount() into two methods
leMaik · Sep 9, 2023 · 8f12ab3 · 8f12ab3
1 parent ba2f58b
commit 8f12ab3
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Showing 4 changed files with 22 additions and 5 deletions.
diff --git a/chunky/src/java/se/llbit/chunky/renderer/PathTracingRenderer.java b/chunky/src/java/se/llbit/chunky/renderer/PathTracingRenderer.java
@@ -71,7 +71,7 @@ public void render(DefaultRenderManager manager) throws InterruptedException {
 
     while (scene.spp < scene.getTargetSpp()) {
       int spp = scene.spp;
-      int branchCount = (tracer instanceof PathTracer) ? scene.getBranchCount() : 1;
+      int branchCount = (tracer instanceof PathTracer) ? scene.getCurrentBranchCount() : 1;
       double sinv = 1.0 / (sppPerPass * branchCount + spp);
 
       submitTiles(manager, (state, pixel) -> {

diff --git a/chunky/src/java/se/llbit/chunky/renderer/scene/PathTracer.java b/chunky/src/java/se/llbit/chunky/renderer/scene/PathTracer.java
@@ -135,7 +135,7 @@ public static boolean pathTrace(Scene scene, Ray ray, WorkerState state, int add
       // The main caveat is that antialiasing is achieved by varying the starting rays at the subpixel level (see PathTracingRenderer.java)
       // Therefore, it's still necessary to have a decent amount (20 is ok, 50 is better) of distinct starting rays for each pixel
       // scene.branchCount is the number of times we use the same first ray before casting a new one
-      int count = firstReflection ? scene.getBranchCount() : 1;
+      int count = firstReflection ? scene.getCurrentBranchCount() : 1;
       for (int i = 0; i < count; i++) {
         boolean doMetal = pMetal > Ray.EPSILON && random.nextFloat() < pMetal;
         if (doMetal || (pSpecular > Ray.EPSILON && random.nextFloat() < pSpecular)) {

diff --git a/chunky/src/java/se/llbit/chunky/renderer/scene/Scene.java b/chunky/src/java/se/llbit/chunky/renderer/scene/Scene.java
@@ -1920,10 +1920,27 @@ public void setTargetSpp(int value) {
   }
 
   /**
-   * @return The branch count
+   * @return The "nominal" value of the branch count.
    */
   public int getBranchCount() {
-    return branchCount;
+      return branchCount;
+  }
+
+  /**
+   * Usually the same as getBranchCount, but reduces branch count to 1 for first few SPP.
+   *
+   * @return The current "true" branch count
+   */
+  public int getCurrentBranchCount() {
+    if(spp < branchCount) {
+      if(spp <= Math.sqrt(branchCount)) { // This is arbitrary, but should be a good compromise in most cases
+        return 1;
+      } else {
+        return branchCount - spp;
+      }
+    } else {
+      return branchCount;
+    }
   }
 
   /**

diff --git a/lib/src/se/llbit/chunky/PersistentSettings.java b/lib/src/se/llbit/chunky/PersistentSettings.java
@@ -64,7 +64,7 @@ public final class PersistentSettings {
   public static final double DEFAULT_FOG_BLUE = 1;
 
   public static final int DEFAULT_RAY_DEPTH = 5;
-  public static final int DEFAULT_BRANCH_COUNT = 5;
+  public static final int DEFAULT_BRANCH_COUNT = 10;
   public static final int DEFAULT_SPP_TARGET = 1000;
 
   public static final int DEFAULT_DIMENSION = 0;