Images: change alpha settings to support channel packing

This also replaces the Use Alpha setting. We now have these alpha modes:

* Straight: store RGB and alpha channels separately with alpha acting as a
  mask, also known as unassociated alpha.
* Premultiplied: transparent RGB pixels are multiplied by the alpha channel.
  The natural format for renders.
* Channel Packed: different images are packed in the RGB and alpha channels,
  and they should not influence each other. Channel packing is commonly used
  by game engines to save memory.
* None: ignore alpha channel from the file and make image fully opaque.

Cycles OSL does not correctly support Channel Packed and None yet, we are
missing fine control over the OpenImageIO texture cache to do that.

Fixes T53672

1 files changed, 41 insertions, 23 deletions

diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index 3905189c8b0..c5b0f6a1e79 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -210,7 +210,13 @@ NODE_DEFINE(ImageTextureNode)
   SOCKET_STRING(filename, "Filename", ustring());
   SOCKET_STRING(colorspace, "Colorspace", u_colorspace_auto);
 
-  SOCKET_BOOLEAN(use_alpha, "Use Alpha", true);
+  static NodeEnum alpha_type_enum;
+  alpha_type_enum.insert("auto", IMAGE_ALPHA_AUTO);
+  alpha_type_enum.insert("unassociated", IMAGE_ALPHA_UNASSOCIATED);
+  alpha_type_enum.insert("associated", IMAGE_ALPHA_ASSOCIATED);
+  alpha_type_enum.insert("channel_packed", IMAGE_ALPHA_CHANNEL_PACKED);
+  alpha_type_enum.insert("ignore", IMAGE_ALPHA_IGNORE);
+  SOCKET_ENUM(alpha_type, "Alpha Type", alpha_type_enum, IMAGE_ALPHA_AUTO);
 
   static NodeEnum interpolation_enum;
   interpolation_enum.insert("closest", INTERPOLATION_CLOSEST);
@@ -257,7 +263,7 @@ ImageTextureNode::~ImageTextureNode()
 {
   if (image_manager) {
     image_manager->remove_image(
-        filename.string(), builtin_data, interpolation, extension, use_alpha, colorspace);
+        filename.string(), builtin_data, interpolation, extension, alpha_type, colorspace);
   }
 }
 
@@ -300,12 +306,12 @@ void ImageTextureNode::compile(SVMCompiler &compiler)
                                     0,
                                     interpolation,
                                     extension,
-                                    use_alpha,
+                                    alpha_type,
                                     colorspace,
                                     metadata);
     is_float = metadata.is_float;
     compress_as_srgb = metadata.compress_as_srgb;
-    colorspace = metadata.colorspace;
+    known_colorspace = metadata.colorspace;
   }
 
   if (slot != -1) {
@@ -317,7 +323,8 @@ void ImageTextureNode::compile(SVMCompiler &compiler)
     }
     if (!alpha_out->links.empty()) {
       const bool unassociate_alpha = !(ColorSpaceManager::colorspace_is_data(colorspace) ||
-                                       use_alpha == false);
+                                       alpha_type == IMAGE_ALPHA_CHANNEL_PACKED ||
+                                       alpha_type == IMAGE_ALPHA_IGNORE);
 
       if (unassociate_alpha) {
         flags |= NODE_IMAGE_ALPHA_UNASSOCIATE;
@@ -378,29 +385,30 @@ void ImageTextureNode::compile(OSLCompiler &compiler)
                                       0,
                                       interpolation,
                                       extension,
-                                      use_alpha,
+                                      alpha_type,
                                       colorspace,
                                       metadata);
     }
     is_float = metadata.is_float;
     compress_as_srgb = metadata.compress_as_srgb;
-    colorspace = metadata.colorspace;
+    known_colorspace = metadata.colorspace;
   }
 
   if (slot == -1) {
-    compiler.parameter_texture("filename", filename, colorspace);
+    compiler.parameter_texture("filename", filename, known_colorspace);
   }
   else {
     compiler.parameter_texture("filename", slot);
   }
 
   const bool unassociate_alpha = !(ColorSpaceManager::colorspace_is_data(colorspace) ||
-                                   use_alpha == false);
+                                   alpha_type == IMAGE_ALPHA_CHANNEL_PACKED ||
+                                   alpha_type == IMAGE_ALPHA_IGNORE);
 
   compiler.parameter(this, "projection");
   compiler.parameter(this, "projection_blend");
-  compiler.parameter("convert_from_srgb", compress_as_srgb);
-  compiler.parameter("ignore_alpha", !use_alpha);
+  compiler.parameter("compress_as_srgb", compress_as_srgb);
+  compiler.parameter("ignore_alpha", alpha_type == IMAGE_ALPHA_IGNORE);
   compiler.parameter("unassociate_alpha", !alpha_out->links.empty() && unassociate_alpha);
   compiler.parameter("is_float", is_float);
   compiler.parameter(this, "interpolation");
@@ -420,7 +428,13 @@ NODE_DEFINE(EnvironmentTextureNode)
   SOCKET_STRING(filename, "Filename", ustring());
   SOCKET_STRING(colorspace, "Colorspace", u_colorspace_auto);
 
-  SOCKET_BOOLEAN(use_alpha, "Use Alpha", true);
+  static NodeEnum alpha_type_enum;
+  alpha_type_enum.insert("auto", IMAGE_ALPHA_AUTO);
+  alpha_type_enum.insert("unassociated", IMAGE_ALPHA_UNASSOCIATED);
+  alpha_type_enum.insert("associated", IMAGE_ALPHA_ASSOCIATED);
+  alpha_type_enum.insert("channel_packed", IMAGE_ALPHA_CHANNEL_PACKED);
+  alpha_type_enum.insert("ignore", IMAGE_ALPHA_IGNORE);
+  SOCKET_ENUM(alpha_type, "Alpha Type", alpha_type_enum, IMAGE_ALPHA_AUTO);
 
   static NodeEnum interpolation_enum;
   interpolation_enum.insert("closest", INTERPOLATION_CLOSEST);
@@ -457,7 +471,7 @@ EnvironmentTextureNode::~EnvironmentTextureNode()
 {
   if (image_manager) {
     image_manager->remove_image(
-        filename.string(), builtin_data, interpolation, EXTENSION_REPEAT, use_alpha, colorspace);
+        filename.string(), builtin_data, interpolation, EXTENSION_REPEAT, alpha_type, colorspace);
   }
 }
 
@@ -498,12 +512,12 @@ void EnvironmentTextureNode::compile(SVMCompiler &compiler)
                                     0,
                                     interpolation,
                                     EXTENSION_REPEAT,
-                                    use_alpha,
+                                    alpha_type,
                                     colorspace,
                                     metadata);
     is_float = metadata.is_float;
     compress_as_srgb = metadata.compress_as_srgb;
-    colorspace = metadata.colorspace;
+    known_colorspace = metadata.colorspace;
   }
 
   if (slot != -1) {
@@ -558,17 +572,17 @@ void EnvironmentTextureNode::compile(OSLCompiler &compiler)
                                       0,
                                       interpolation,
                                       EXTENSION_REPEAT,
-                                      use_alpha,
+                                      alpha_type,
                                       colorspace,
                                       metadata);
     }
     is_float = metadata.is_float;
     compress_as_srgb = metadata.compress_as_srgb;
-    colorspace = metadata.colorspace;
+    known_colorspace = metadata.colorspace;
   }
 
   if (slot == -1) {
-    compiler.parameter_texture("filename", filename, colorspace);
+    compiler.parameter_texture("filename", filename, known_colorspace);
   }
   else {
     compiler.parameter_texture("filename", slot);
@@ -576,8 +590,8 @@ void EnvironmentTextureNode::compile(OSLCompiler &compiler)
 
   compiler.parameter(this, "projection");
   compiler.parameter(this, "interpolation");
-  compiler.parameter("convert_from_srgb", compress_as_srgb);
-  compiler.parameter("ignore_alpha", !use_alpha);
+  compiler.parameter("compress_as_srgb", compress_as_srgb);
+  compiler.parameter("ignore_alpha", alpha_type == IMAGE_ALPHA_IGNORE);
   compiler.parameter("is_float", is_float);
   compiler.add(this, "node_environment_texture");
 }
@@ -1490,8 +1504,12 @@ PointDensityTextureNode::PointDensityTextureNode() : ShaderNode(node_type)
 PointDensityTextureNode::~PointDensityTextureNode()
 {
   if (image_manager) {
-    image_manager->remove_image(
-        filename.string(), builtin_data, interpolation, EXTENSION_CLIP, true, ustring());
+    image_manager->remove_image(filename.string(),
+                                builtin_data,
+                                interpolation,
+                                EXTENSION_CLIP,
+                                IMAGE_ALPHA_AUTO,
+                                ustring());
   }
 }
 
@@ -1524,7 +1542,7 @@ void PointDensityTextureNode::add_image()
                                     0,
                                     interpolation,
                                     EXTENSION_CLIP,
-                                    true,
+                                    IMAGE_ALPHA_AUTO,
                                     u_colorspace_raw,
                                     metadata);
   }