From 37bcdf51fc7b3d1bbb4be0bbb1747c9deb0a339c Mon Sep 17 00:00:00 2001
From: Maik Marschner <leMaik@leMaik.de>
Date: Sun, 27 Oct 2024 18:48:07 +0100
Subject: [PATCH] Fix transparent sky not working with render regions. (#1790)

---
 .../chunky/renderer/scene/AlphaBuffer.java     | 18 +++++++++++-------
 .../se/llbit/chunky/renderer/scene/Scene.java  |  4 ++--
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/chunky/src/java/se/llbit/chunky/renderer/scene/AlphaBuffer.java b/chunky/src/java/se/llbit/chunky/renderer/scene/AlphaBuffer.java
index 10198a784c..0562b8aab1 100644
--- a/chunky/src/java/se/llbit/chunky/renderer/scene/AlphaBuffer.java
+++ b/chunky/src/java/se/llbit/chunky/renderer/scene/AlphaBuffer.java
@@ -72,8 +72,12 @@ void computeAlpha(Scene scene, Type type, TaskTracker taskTracker) {
 
     try (TaskTracker.Task task = taskTracker.task("Computing alpha channel")) {
       this.type = type;
+      int cropX = scene.canvasConfig.getCropX();
+      int cropY = scene.canvasConfig.getCropY();
       int width = scene.canvasConfig.getWidth();
       int height = scene.canvasConfig.getHeight();
+      int fullWidth = scene.canvasConfig.getCropWidth();
+      int fullHeight = scene.canvasConfig.getCropHeight();
       buffer = ByteBuffer.allocate(scene.canvasConfig.getPixelCount() * type.byteSize);
 
       AtomicInteger done = new AtomicInteger(0);
@@ -83,10 +87,10 @@ void computeAlpha(Scene scene, Type type, TaskTracker taskTracker) {
           state.ray = new Ray();
 
           for (int y = 0; y < height; y++) {
-            computeAlpha(scene, x, y, width, height, state);
+            computeAlpha(scene, x, y, cropX, cropY, width, height, fullWidth, fullHeight, state);
           }
 
-          task.update(width, done.incrementAndGet());
+          task.update(height, done.incrementAndGet());
         });
       }).get();
     } catch (InterruptedException | ExecutionException e) {
@@ -97,10 +101,10 @@ void computeAlpha(Scene scene, Type type, TaskTracker taskTracker) {
   /**
    * Compute the alpha channel based on sky visibility.
    */
-  public void computeAlpha(Scene scene, int x, int y, int width, int height, WorkerState state) {
+  public void computeAlpha(Scene scene, int x, int y, int cropX, int cropY, int width, int height, int fullWidth, int fullHeight, WorkerState state) {
     Ray ray = state.ray;
-    double halfWidth = width / (2.0 * height);
-    double invHeight = 1.0 / height;
+    double halfWidth = fullWidth / (2.0 * fullHeight);
+    double invHeight = 1.0 / fullHeight;
 
     // Rotated grid supersampling.
     double[][] offsets = new double[][]{
@@ -113,8 +117,8 @@ public void computeAlpha(Scene scene, int x, int y, int width, int height, Worke
     double occlusion = 0.0;
     for (double[] offset : offsets) {
       scene.camera.calcViewRay(ray,
-        -halfWidth + (x + offset[0]) * invHeight,
-        -0.5 + (y + offset[1]) * invHeight);
+        -halfWidth + (x + offset[0] + cropX) * invHeight,
+        -0.5 + (y + offset[1] + cropY) * invHeight);
       ray.o.x -= scene.origin.x;
       ray.o.y -= scene.origin.y;
       ray.o.z -= scene.origin.z;
diff --git a/chunky/src/java/se/llbit/chunky/renderer/scene/Scene.java b/chunky/src/java/se/llbit/chunky/renderer/scene/Scene.java
index 4afb6c46ef..e2770c1cac 100644
--- a/chunky/src/java/se/llbit/chunky/renderer/scene/Scene.java
+++ b/chunky/src/java/se/llbit/chunky/renderer/scene/Scene.java
@@ -2060,9 +2060,9 @@ public synchronized void writeFrame(OutputStream out, PictureExportFormat mode,
     if (transparentSky) {
       if (mode.getTransparencyType() == AlphaBuffer.Type.UNSUPPORTED) {
         Log.warn("You selected \"transparent sky\", but the selected picture format \"" + mode.getName() + "\" does not support alpha layers.\nUse a different format like PNG instead.");
-        }
-      alphaBuffer.computeAlpha(this, mode.getTransparencyType(), taskTracker);
       }
+      alphaBuffer.computeAlpha(this, mode.getTransparencyType(), taskTracker);
+    }
     if (mode.wantsPostprocessing() && !finalized) {
       postProcessFrame(taskTracker);
     }