Cycles: refactor API for render output

* Add OutputDriver, replacing function callbacks in Session.
* Add PathTraceTile, replacing tile access methods in Session.
* Add more detailed comments about how this driver should be implemented.
* Add OIIOOutputDriver for Cycles standalone to output an image.

Differential Revision: https://developer.blender.org/D12627

1 files changed, 71 insertions, 0 deletions

diff --git a/intern/cycles/app/oiio_output_driver.cpp b/intern/cycles/app/oiio_output_driver.cpp
new file mode 100644
index 00000000000..d791c89772f
--- /dev/null
+++ b/intern/cycles/app/oiio_output_driver.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2021 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "app/oiio_output_driver.h"
+
+CCL_NAMESPACE_BEGIN
+
+OIIOOutputDriver::OIIOOutputDriver(const string_view filepath,
+                                   const string_view pass,
+                                   LogFunction log)
+    : filepath_(filepath), pass_(pass), log_(log)
+{
+}
+
+OIIOOutputDriver::~OIIOOutputDriver()
+{
+}
+
+void OIIOOutputDriver::write_render_tile(const Tile &tile)
+{
+  /* Only write the full buffer, no intermediate tiles. */
+  if (!(tile.size == tile.full_size)) {
+    return;
+  }
+
+  log_(string_printf("Writing image %s", filepath_.c_str()));
+
+  unique_ptr<ImageOutput> image_output(ImageOutput::create(filepath_));
+  if (image_output == nullptr) {
+    log_("Failed to create image file");
+    return;
+  }
+
+  const int width = tile.size.x;
+  const int height = tile.size.y;
+
+  ImageSpec spec(width, height, 4, TypeDesc::FLOAT);
+  if (!image_output->open(filepath_, spec)) {
+    log_("Failed to create image file");
+    return;
+  }
+
+  vector<float> pixels(width * height * 4);
+  if (!tile.get_pass_pixels(pass_, 4, pixels.data())) {
+    log_("Failed to read render pass pixels");
+    return;
+  }
+
+  /* Manipulate offset and stride to convert from bottom-up to top-down convention. */
+  image_output->write_image(TypeDesc::FLOAT,
+                            pixels.data() + (height - 1) * width * 4,
+                            AutoStride,
+                            -width * 4 * sizeof(float),
+                            AutoStride);
+  image_output->close();
+}
+
+CCL_NAMESPACE_END