In Nature Simulation Sys. Inc., v. Autodesk, Inc., 2022 U.S. App. LEXIS 28654, 50 F.4th 1358 (Fed. Cir. 2022), Nature Simulation Systems Inc. (“NSS”) found relief at the Federal Circuit when a majority panel reversed the Northern District of California’s decision that their method patents for performing computer-aided operations for three-dimensional objects were invalid as indefinite. The Federal Circuit majority, composed of Judges Newman and Lourie, held the district court improperly disregarded specification language. Furthermore, the majority held that in light of the disregarded specification language, the challenged claims were definite.

U.S. Patent Nos. 10,109,105 and 10,120,961 relate to a computer-implemented method for building three-dimensional objects employing a computation method called “Boolean operation.” The patents are for data structures and algorithms for the claimed method, which is described as a modification of a known Boolean operation for analyzing and representing three-dimensional geographic shapes (“the Watson method”). Id. at *3. The patents state that the claimed method provides simplicity and flexibility compared with prior programs and is easier to program and implement. Id. at *4.

District Court

In an infringement suit brought by NSS, Autodesk alleged the asserted patents were invalid as indefinite under 35 U.S.C. § 112(b). The district court found the following two claim phrases indefinite in the asserted patents: (1) “searching neighboring triangles of the last triangle pair that holds the last intersection point,” and (2) “modified Watson method.” According to the district court there were “unanswered questions” raised by Autodesk’s experts in defining these terms that were not answered within the claim language itself. Id. at *7.

The district court’s indefiniteness standard required that all questions be answered within the claim language alone, without consideration of the specification language or prosecution history. Id. at *11.

Federal Circuit

The Federal Circuit majority reversed the district court decision, finding that the district court applied the incorrect standard of “unanswered questions.” Id. at *17. The majority’s opinion explained that “[c]laim language, standing alone,” is not the correct standard of law. Id. at *12. Rather, the test is that set forth in Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 910 (2014):

we read § 112, ¶ 2 to require that a patent’s claims, viewed in light of the specification and prosecution history, inform those skilled in the art about the scope of the invention with reasonable certainty.

Nature Simulation, at *9.

Applying the correct standard, the majority held that the specification provided information that answered the questions raised by Autodesk’s expert and, therefore, the challenged claims were not invalid as indefinite. With respect to the “last intersection” term, the majority cited (1) specification language that explained how the intersection line was built and where it was located; (2) a flow chart explaining the intersection line; and (3) specification language that described how the invention is used and modified compared to the known Watson method. Id. at *12–13. With respect to the “modified Watson method,” the majority looked to figures and language in the specification describing the prior art method. Id. at *15–16.

The majority also cited the prosecution history for support that the claims were not indefinite. Id. at *17. During prosecution, the examiner initially rejected the claims for indefiniteness because the examiner questioned, “What is causing the closure of the intersection lines?” and their relation to the neighboring triangle was unclear. Id. at *18. To overcome this rejection, NSS amended the claims to specify the closing of the intersecting lines and their relation with the neighboring triangles. Id. The majority noted the examiner removed the rejection in light of the amendment and those amended claims distinguished the invention from the prior art. Id. at *19. It was improper for the district court to neglect the prosecution history in an indefiniteness analysis. Id. at *21.

The majority reversed the district court decision and remanded for further proceedings.


In a dissenting opinion, Judge Dyk agreed with the majority’s standard for indefiniteness. He disagreed, however, as to whether the specification provided adequate information to answer the questions raised by Autodesk’s expert. Id. at *25. Judge Dyk argued that nothing in the specification defined a modified Watson method or explained the intersection line. Id. at *28. Additionally, Judge Dyk disagreed with the majority’s view that the District Court disregarded the specification and prosecution history. Id. at *29. He pointed out that nowhere in the district court’s decision did it state that “claim language, standing alone” is the standard for indefiniteness. Id. at *22. He stated that the majority improperly cited this language from Autodesk’s declaration. Id.


This case serves as an important reminder that when trying to overcome a 35 U.S.C. § 112(b) invalidity argument, whether in court or in the USPTO, the standard is one of “reasonable certainty” to one of ordinary skill in the art and that may be achieved not only via the claim language alone, but also through the specification and prosecution history.

This opinion first issued Jan. 27, 2022, and was then modified and reissued Oct. 17, 2022, following a petition for rehearing filed by Autodesk.