Assorted fixes to UV unwrapping and GPU lightmapper

Various fixes to UV2 unwrapping and the GPU lightmapper. Listed here for
context in case of git blame/bisect:

* Fix UV2 unwrapping on import, also cleaned up the unwrap cache code.
* Fix saving of RGBA images in EXR format.
* Fixes to the GPU lightmapper:
	- Added padding between atlas elements, avoids bleeding.
	- Remove old SDF generation code.
	- Fix baked attenuation for Omni/Spot lights.
	- Fix baking of material properties onto UV2 (wireframe was
	  wrongly used before).
	- Disable statically baked lights for objects that have a
	  lightmap texture to avoid applying the same light twice.
	- Fix lightmap pairing in RendererSceneCull.
	- Fix UV2 array generated from `RenderingServer::mesh_surface_get_arrays()`.
	- Port autoexposure fix for OIDN from 3.x.
	- Save debug textures as EXR when using floating point format.

2 files changed, 103 insertions, 72 deletions

diff --git a/thirdparty/oidn/core/transfer_function.cpp b/thirdparty/oidn/core/transfer_function.cpp
index 487f0a9f75..ce5deca56b 100644
--- a/thirdparty/oidn/core/transfer_function.cpp
+++ b/thirdparty/oidn/core/transfer_function.cpp
@@ -24,10 +24,6 @@ namespace oidn {
   float AutoexposureNode::autoexposure(const Image& color)
   {
     assert(color.format == Format::Float3);
-// -- GODOT start --
-// We don't want to mess with TTB and we don't use autoexposure, so we disable this code
-#if 0
-// -- GODOT end --
 
     constexpr float key = 0.18f;
     constexpr float eps = 1e-8f;
@@ -42,61 +38,66 @@ namespace oidn {
     // Compute the average log luminance of the downsampled image
     using Sum = std::pair<float, int>;
 
-    Sum sum =
-      tbb::parallel_reduce(
-        tbb::blocked_range2d<int>(0, HK, 0, WK),
-        Sum(0.f, 0),
-        [&](const tbb::blocked_range2d<int>& r, Sum sum) -> Sum
+    // -- GODOT start --
+    // Sum sum =
+    //   tbb::parallel_reduce(
+    //     tbb::blocked_range2d<int>(0, HK, 0, WK),
+    //     Sum(0.f, 0),
+    //     [&](const tbb::blocked_range2d<int>& r, Sum sum) -> Sum
+    //     {
+    //       // Iterate over blocks
+    //       for (int i = r.rows().begin(); i != r.rows().end(); ++i)
+    //       {
+    //         for (int j = r.cols().begin(); j != r.cols().end(); ++j)
+    //         {
+
+    Sum sum = Sum(0.0f, 0);
+
+    for (int i = 0; i != HK; ++i)
+    {
+      for (int j = 0; j != WK; ++j)
+      {
+        // Compute the average luminance in the current block
+        const int beginH = int(ptrdiff_t(i)   * H / HK);
+        const int beginW = int(ptrdiff_t(j)   * W / WK);
+        const int endH   = int(ptrdiff_t(i+1) * H / HK);
+        const int endW   = int(ptrdiff_t(j+1) * W / WK);
+
+        float L = 0.f;
+
+        for (int h = beginH; h < endH; ++h)
         {
-          // Iterate over blocks
-          for (int i = r.rows().begin(); i != r.rows().end(); ++i)
+          for (int w = beginW; w < endW; ++w)
           {
-            for (int j = r.cols().begin(); j != r.cols().end(); ++j)
-            {
-              // Compute the average luminance in the current block
-              const int beginH = int(ptrdiff_t(i)   * H / HK);
-              const int beginW = int(ptrdiff_t(j)   * W / WK);
-              const int endH   = int(ptrdiff_t(i+1) * H / HK);
-              const int endW   = int(ptrdiff_t(j+1) * W / WK);
-
-              float L = 0.f;
-
-              for (int h = beginH; h < endH; ++h)
-              {
-                for (int w = beginW; w < endW; ++w)
-                {
-                  const float* rgb = (const float*)color.get(h, w);
-
-                  const float r = maxSafe(rgb[0], 0.f);
-                  const float g = maxSafe(rgb[1], 0.f);
-                  const float b = maxSafe(rgb[2], 0.f);
-
-                  L += luminance(r, g, b);
-                }
-              }
-
-              L /= (endH - beginH) * (endW - beginW);
-
-              // Accumulate the log luminance
-              if (L > eps)
-              {
-                sum.first += log2(L);
-                sum.second++;
-              }
-            }
+            const float* rgb = (const float*)color.get(h, w);
+
+            const float r = maxSafe(rgb[0], 0.f);
+            const float g = maxSafe(rgb[1], 0.f);
+            const float b = maxSafe(rgb[2], 0.f);
+
+            L += luminance(r, g, b);
           }
+        }
 
-          return sum;
-        },
-        [](Sum a, Sum b) -> Sum { return Sum(a.first+b.first, a.second+b.second); },
-        tbb::static_partitioner()
-      );
+        L /= (endH - beginH) * (endW - beginW);
+
+        // Accumulate the log luminance
+        if (L > eps)
+        {
+          sum.first += log2(L);
+          sum.second++;
+        }
+      }
+    }
+
+    //     return sum;
+    //   },
+    //   [](Sum a, Sum b) -> Sum { return Sum(a.first+b.first, a.second+b.second); },
+    //   tbb::static_partitioner()
+    // );
+    // -- GODOT end --
 
     return (sum.second > 0) ? (key / exp2(sum.first / float(sum.second))) : 1.f;
-// -- GODOT start --
-#endif
-    return 1.0;
-// -- GODOT end --
   }
 
 } // namespace oidn
diff --git a/thirdparty/oidn/patches/godot-changes-c58c5216.patch b/thirdparty/oidn/patches/godot-changes-c58c5216.patch
index 6a54703064..c01f00187b 100644
--- a/thirdparty/oidn/patches/godot-changes-c58c5216.patch
+++ b/thirdparty/oidn/patches/godot-changes-c58c5216.patch
@@ -280,28 +280,58 @@ index 8c2de09..ed8328c 100644
  namespace oidn {
  
 diff --git a/core/transfer_function.cpp b/core/transfer_function.cpp
-index 601f814..487f0a9 100644
+index 601f814..ce5deca 100644
 --- a/core/transfer_function.cpp
 +++ b/core/transfer_function.cpp
-@@ -24,6 +24,10 @@ namespace oidn {
-   float AutoexposureNode::autoexposure(const Image& color)
-   {
-     assert(color.format == Format::Float3);
-+// -- GODOT start --
-+// We don't want to mess with TTB and we don't use autoexposure, so we disable this code
-+#if 0
-+// -- GODOT end --
+@@ -38,16 +38,24 @@ namespace oidn {
+     // Compute the average log luminance of the downsampled image
+     using Sum = std::pair<float, int>;
+ 
+-    Sum sum =
+-      tbb::parallel_reduce(
+-        tbb::blocked_range2d<int>(0, HK, 0, WK),
+-        Sum(0.f, 0),
+-        [&](const tbb::blocked_range2d<int>& r, Sum sum) -> Sum
++    // -- GODOT start --
++    // Sum sum =
++    //   tbb::parallel_reduce(
++    //     tbb::blocked_range2d<int>(0, HK, 0, WK),
++    //     Sum(0.f, 0),
++    //     [&](const tbb::blocked_range2d<int>& r, Sum sum) -> Sum
++    //     {
++    //       // Iterate over blocks
++    //       for (int i = r.rows().begin(); i != r.rows().end(); ++i)
++    //       {
++    //         for (int j = r.cols().begin(); j != r.cols().end(); ++j)
++    //         {
++
++    Sum sum = Sum(0.0f, 0);
++
++    for (int i = 0; i != HK; ++i)
+     {
+-          // Iterate over blocks
+-          for (int i = r.rows().begin(); i != r.rows().end(); ++i)
+-          {
+-            for (int j = r.cols().begin(); j != r.cols().end(); ++j)
++      for (int j = 0; j != WK; ++j)
+       {
+         // Compute the average luminance in the current block
+         const int beginH = int(ptrdiff_t(i)   * H / HK);
+@@ -82,11 +90,12 @@ namespace oidn {
+       }
+     }
  
-     constexpr float key = 0.18f;
-     constexpr float eps = 1e-8f;
-@@ -89,6 +93,10 @@ namespace oidn {
-       );
+-          return sum;
+-        },
+-        [](Sum a, Sum b) -> Sum { return Sum(a.first+b.first, a.second+b.second); },
+-        tbb::static_partitioner()
+-      );
++    //     return sum;
++    //   },
++    //   [](Sum a, Sum b) -> Sum { return Sum(a.first+b.first, a.second+b.second); },
++    //   tbb::static_partitioner()
++    // );
++    // -- GODOT end --
  
      return (sum.second > 0) ? (key / exp2(sum.first / float(sum.second))) : 1.f;
-+// -- GODOT start --
-+#endif
-+    return 1.0;
-+// -- GODOT end --
    }
- 
- } // namespace oidn