Create a simplified Falcor material system in slang test (#2721)

* Duplicate an example of differentiating Falcor's material system

* Add a second BSDF

* WIP: update test; grad didn't pass through

* Finalize test

---------

Co-authored-by: Lifan Wu <lifanw@nvidia.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/autodiff/material/DiffuseMaterialInstance.slang b/tests/autodiff/material/DiffuseMaterialInstance.slang
new file mode 100644
index 000000000..ca6bfc69a
--- /dev/null
+++ b/tests/autodiff/material/DiffuseMaterialInstance.slang
@@ -0,0 +1,26 @@
+//TEST_IGNORE_FILE:
+
+__exported import IMaterialInstance;
+__exported import IBSDF;
+
+struct DiffuseBSDF : IBSDF
+{
+    float3 albedo;
+
+    [TreatAsDifferentiable]
+    float3 eval(const float3 wiLocal, const float3 woLocal)
+    {
+        return albedo;
+    }
+};
+
+struct DiffuseMaterialInstance : IMaterialInstance
+{
+    DiffuseBSDF bsdf;
+
+    [TreatAsDifferentiable]
+    float3 eval(const float3 wi, const float3 wo)
+    {
+        return bsdf.eval(wi, wo);
+    }
+};