Compositor: Expose Alpha socket for multilayer EXR node

This way re-mapping scene nodes to EXR files becomes much easier,
no extra trickery with separate RGBA setups is needed.

Plus makes it more consistent with regular EXR files.

This uses EGBA pass to get alpha from.

2 files changed, 49 insertions, 25 deletions

diff --git a/source/blender/compositor/nodes/COM_ImageNode.cpp b/source/blender/compositor/nodes/COM_ImageNode.cpp
index e105f530eb2..cb7ccfaedf9 100644
--- a/source/blender/compositor/nodes/COM_ImageNode.cpp
+++ b/source/blender/compositor/nodes/COM_ImageNode.cpp
@@ -32,6 +32,7 @@
 #include "COM_SetValueOperation.h"
 #include "COM_SetVectorOperation.h"
 #include "COM_SetColorOperation.h"
+#include "COM_SeparateColorNode.h"
 
 ImageNode::ImageNode(bNode *editorNode) : Node(editorNode)
 {
@@ -78,7 +79,7 @@ void ImageNode::convertToOperations(NodeConverter &converter, const CompositorCo
 	int numberOfOutputs = this->getNumberOfOutputSockets();
 	bool outputStraightAlpha = (editorNode->custom1 & CMP_NODE_IMAGE_USE_STRAIGHT_OUTPUT) != 0;
 	BKE_image_user_frame_calc(imageuser, context.getFramenumber(), 0);
-
+	NodeOperation *combined_operation = NULL;
 	/* force a load, we assume iuser index will be set OK anyway */
 	if (image && image->type == IMA_TYPE_MULTILAYER) {
 		bool is_multilayer_ok = false;
@@ -105,33 +106,48 @@ void ImageNode::convertToOperations(NodeConverter &converter, const CompositorCo
 #endif
 					int passindex;
 					RenderPass *rpass;
-					for (rpass = (RenderPass *)rl->passes.first, passindex = 0; rpass; rpass = rpass->next, ++passindex)
-						if (STREQ(rpass->name, bnodeSocket->identifier))
-							break;
-					if (rpass) {
-						imageuser->pass = passindex;
-						switch (rpass->channels) {
-							case 1:
-								operation = doMultilayerCheck(converter, rl, image, imageuser, framenumber, index, passindex, COM_DT_VALUE);
-								break;
-								/* using image operations for both 3 and 4 channels (RGB and RGBA respectively) */
-								/* XXX any way to detect actual vector images? */
-							case 3:
-								operation = doMultilayerCheck(converter, rl, image, imageuser, framenumber, index, passindex, COM_DT_VECTOR);
-								break;
-							case 4:
-								operation = doMultilayerCheck(converter, rl, image, imageuser, framenumber, index, passindex, COM_DT_COLOR);
-								break;
-							default:
-								/* dummy operation is added below */
+					if (STREQ(bnodeSocket->identifier, "Alpha")) {
+						BLI_assert(combined_operation != NULL);
+						NodeOutput *outputSocket = this->getOutputSocket(index);
+						SeparateChannelOperation *separate_operation;
+						separate_operation = new SeparateChannelOperation();
+						separate_operation->setChannel(3);
+						converter.addOperation(separate_operation);
+						converter.addLink(combined_operation->getOutputSocket(), separate_operation->getInputSocket(0));
+						converter.mapOutputSocket(outputSocket, separate_operation->getOutputSocket());
+						operation = separate_operation;
+					}
+					else {
+						for (rpass = (RenderPass *)rl->passes.first, passindex = 0; rpass; rpass = rpass->next, ++passindex)
+							if (STREQ(rpass->name, bnodeSocket->identifier))
 								break;
-						}
-						
-						if (index == 0 && operation) {
-							converter.addPreview(operation->getOutputSocket());
+						if (rpass) {
+							imageuser->pass = passindex;
+							switch (rpass->channels) {
+								case 1:
+									operation = doMultilayerCheck(converter, rl, image, imageuser, framenumber, index, passindex, COM_DT_VALUE);
+									break;
+									/* using image operations for both 3 and 4 channels (RGB and RGBA respectively) */
+									/* XXX any way to detect actual vector images? */
+								case 3:
+									operation = doMultilayerCheck(converter, rl, image, imageuser, framenumber, index, passindex, COM_DT_VECTOR);
+									break;
+								case 4:
+									operation = doMultilayerCheck(converter, rl, image, imageuser, framenumber, index, passindex, COM_DT_COLOR);
+									break;
+								default:
+									/* dummy operation is added below */
+									break;
+							}
+							if (index == 0 && operation) {
+								converter.addPreview(operation->getOutputSocket());
+							}
+							if (STREQ(rpass->chan_id, "RGBA")) {
+								combined_operation = operation;
+							}
 						}
 					}
-					
+
 					/* incase we can't load the layer */
 					if (operation == NULL)
 						converter.setInvalidOutput(getOutputSocket(index));
diff --git a/source/blender/nodes/composite/nodes/node_composite_image.c b/source/blender/nodes/composite/nodes/node_composite_image.c
index e8845b543b8..34f3350c2ff 100644
--- a/source/blender/nodes/composite/nodes/node_composite_image.c
+++ b/source/blender/nodes/composite/nodes/node_composite_image.c
@@ -182,6 +182,14 @@ static void cmp_node_image_add_multilayer_outputs(bNodeTree *ntree, bNode *node,
 		
 		sockdata->pass_index = index;
 		sockdata->pass_flag = rpass->passtype;
+
+		if (STREQ(rpass->chan_id, "RGBA")) {
+			sock = nodeAddStaticSocket(ntree, node, SOCK_OUT, SOCK_FLOAT, PROP_NONE, "Alpha", "Alpha");
+			sockdata = MEM_callocN(sizeof(NodeImageLayer), "node image layer");
+			sock->storage = sockdata;
+			sockdata->pass_index = index;
+			sockdata->pass_flag = rpass->passtype;
+		}
 	}
 }