Make isconnected() work with downstream renderer "connections." (#1782)

The isconnected() returns 2 when used on an output that is connected to another downstream shader node -- this can be used to limit computation to only the outputs used.  However, that misses the important case of where the renderer has declared a shader node output as a renderer output, which happens often when using OSL purely for pattern generation purposes.  This change makes that case also return 2.

The isconnected test has been updated to include testing this functionality.

Signed-off-by: Stephen Friedman <[email protected]>

Author: sfriedmapixar

src/liboslexec/runtimeoptimize.cpp

@@ -2501,7 +2501,8 @@ RuntimeOptimizer::resolve_isconnected()
             bool upconnected = s->connected();
             if (s->interpolated() && shadingsys().userdata_isconnected())
                 upconnected = true;
-            int val = (upconnected ? 1 : 0) + (s->connected_down() ? 2 : 0);
+            bool downconnected = s->connected_down() || s->renderer_output();
+            int val = (upconnected ? 1 : 0) + (downconnected ? 2 : 0);
             turn_into_assign(op, add_constant(TypeDesc::TypeInt, &val),
                              "resolve isconnected()");
         }

testsuite/isconnected/ref/out.txt

@@ -2,6 +2,8 @@ Compiled test.osl -> test.oso
 Compiled upstream.osl -> upstream.oso
 Connect upstream.out to downstream.a
 Connect upstream.struct1 to downstream.mystruct1
+
+Output Fout to out.tif
 Upstream:
 out connected: 2  (value=0.5)
 notout connected: 0  (value=10)
@@ -22,7 +24,7 @@ mystruct1.y connected: 1  (value=4)
 mystruct2 connected: 0  (value={0, 0})
 mystruct2.x connected: 0  (value=0)
 mystruct2.y connected: 0  (value=0)
-
+Fout connected: 2  (value=0.42)
 Connect upstream.out to downstream.a
 Connect upstream.struct1 to downstream.mystruct1
 Upstream:
@@ -45,4 +47,5 @@ mystruct1.y connected: 1  (value=4)
 mystruct2 connected: 0  (value={0, 0})
 mystruct2.x connected: 0  (value=0)
 mystruct2.y connected: 0  (value=0)
+Fout connected: 0  (value=0)
 

testsuite/isconnected/run.py

@@ -4,9 +4,11 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # https://github.com/AcademySoftwareFoundation/OpenShadingLanguage
 
-command  = testshade("--layer upstream upstream --layer downstream test " +
+command  = testshade("-g 1 1 -od uint8 -o Fout out.tif " +
+                     "--layer upstream upstream --layer downstream test " +
                      "--connect upstream out downstream a " +
-                     "--connect upstream struct1 downstream mystruct1")
+                     "--connect upstream struct1 downstream mystruct1" 
+                     )
 
 # Run again, this time considering userdata (lockgeom=0) parameters to be
 # isconnected(). This time, parameter c should look like a connection.

testsuite/isconnected/test.osl

@@ -7,7 +7,8 @@
 shader test (float a = 0, float b = 0,
              float c = 0 [[ int lockgeom=0 ]],
              MyStruct mystruct1 = {0,0},
-             MyStruct mystruct2 = {0,0})
+             MyStruct mystruct2 = {0,0},
+             output float Fout = 1)
 {
     printf ("a=%g\n", a);   // force retrieval/execution of upstream layer
     printf ("Downstream:\n");
@@ -16,4 +17,14 @@ shader test (float a = 0, float b = 0,
     status (c, "c");
     status (mystruct1, "mystruct1");
     status (mystruct2, "mystruct2");
+    
+    if (isconnected(Fout) == 2)
+    {
+      Fout = .42;
+    }
+    else
+    {
+      Fout = 0;
+    }
+    status (Fout, "Fout");
 }