POWER OF ATTORNEY

     Known by all those present, that Amy Messano hereby constitutes and
appoints each of Raoul K. Maitra, Steven M. Rivkin, and Brian Gayle as
his/her/its true and lawful attorneys-in-fact with respect to Altair Engineering
Inc. to:

     (1) prepare, execute in the undersigned's name and on the undersigned's
     behalf, and submit to the U.S. Securities and Exchange Commission (the
     "SEC") a Form ID, including amendments thereto, and any other documents
     necessary or appropriate to obtain codes and passwords enabling the
     undersigned to make electronic filings with the SEC of reports required by
     Section 13 and 16(a) of the Securities Exchange Act of 1934, or any rule or
     regulation of the SEC;

     (2) execute for and on behalf of the undersigned Schedules 13D and 13G, and
     Forms 3, 4 and 5 in accordance with Sections 13 and 16(a) of the Securities
     Exchange Act of 1934 and the rules thereunder;

     (3) do and perform any and all acts for and on behalf of the undersigned
     which may be necessary or desirable to complete and execute any such
     Schedules 13D or 13G, and Forms 3, 4, and 5, complete and execute any
     amendment or amendments thereto, and timely file such form with the SEC and
     any stock exchange or similar authority; and

     (4) take any other action of any type whatsoever in connection with the
     foregoing which, in the opinion of such attorney-in-fact, may be of benefit
     to, in the best interest of, or legally required by, the undersigned,
     including without limitation the execution and filing of a Form 4 with
     respect to a transaction which may be reported on a Form 5, it being
     understood that the documents executed by such attorney-in-fact on behalf
     of the undersigned pursuant to this Power of Attorney shall be in such form
     and shall contain such terms and conditions as such attorney-in- fact may
     approve in such attorney in fact's discretion.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact's designated substitute or substitutes, shall lawfully do or
cause to be done by virtue of this Power of Attorney and the rights and powers
herein granted. The undersigned acknowledges that the foregoing attorneys-in-
fact, in serving in such capacity at the request of the undersigned, are not
assuming any of the undersigned's responsibilities to comply with Sections 13
and 16 of the Securities Exchange Act of 1934, as amended, and the rules
thereunder.

     This Power of Attorney shall remain in full force and effect until revoked
by the undersigned in a signed writing delivered to the each foregoing attorney-
in-fact.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 18th day of December, 2018.

                                                /s/ Amy Messano
                                                   ----------------

                                                Name: Amy Messano

Sworn and subscribed before me on December 18, 2018 by Amy Messano.

Stephanie M Roehrig
----------------------
Stephanie M. Roehrig, Notary Public
Oakland County, Michigan
My Commission Expires: October 4, 2021
Acting in Oakland County