<PAGE>

EXHIBIT 4.5
-----------
THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE OFFERED, SOLD OR OTHERWISE
TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT
OR, IN THE OPINION OF COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE COMPANY,
SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE
THEREWITH.

                       SERIES B PREFERRED STOCK WARRANT

                                      of

                            MOAI TECHNOLOGIES, INC.

     THIS CERTIFIES THAT DAVID CAMPBELL (the "Warrantholder") is entitled to
subscribe for and purchase from MOAI TECHNOLOGIES, INC., a California
corporation (the "Company") during the Exercise Period (as defined below) 4,687
fully-paid and non-assessable shares of the Company's SERIES B Preferred Stock
(the "Preferred"), at a price of $1.28 per share (the "Warrant Price"), such
price and such number of shares being subject to adjustment upon the occurrence
of the contingencies set forth in this Warrant.

     Upon delivery of this Warrant, together with payment of the Warrant Price
of the shares of the Preferred thereby purchased, at the principal office of the
Company or at such other office or agency as the Company may designate by notice
in writing to the holder hereof, the holder of this Warrant shall be entitled to
receive a certificate or certificates for the shares of Preferred so purchased.
The date at which the Company receives (i) the Warrant and (ii) payment for the
shares of Preferred, either by payment in cash or by check, or by notice of the
Warrantholder's intent to use the proceeds from the concurrent sale of shares at
a Public Offering (as defined below) or notice of intent to use shares of
Preferred as payment, both as described in Section 1 below, or such later date
as such notice shall specify, shall be referred to herein as the "Exercise
Date." All shares of Preferred which may be issued upon the exercise of this
Warrant will, upon issuance, be fully paid and non-assessable and free from all
taxes, liens and charges with respect thereto.

     This Warrant is subject to the following terms and conditions:

     1.  Exercise of Warrant:  Subject to the terms and conditions set forth
         -------------------
herein, this Warrant may be exercised in whole or in part, at any time on or
before October 5, 2008 by the surrender of this Warrant together with the
"Notice of Exercise" and "Investment Representation Statement" attached hereto
as Exhibits A and B, respectively, duly completed and executed at the principal
office of the Company and by the payment to the Company, in the manner provided
for in the following paragraph, of the Warrant Price for all of the Preferred
purchased. The Company shall, within 10 days after such delivery, prepare a
certificate for the shares of Preferred purchased in the name of the holder of
this Warrant, or as such holder may direct (subject to the restrictions upon
transfer contained herein and upon payment by such holder hereof of any
applicable transfer taxes).
<PAGE>

     This Warrant may be exercised by the payment to the Company, by cash or
check, or from the proceeds of the concurrent sale of shares of Common Stock
issued upon conversion of shares of Preferred issued upon exercise of this
Warrant, sold by the Warrantholder pursuant to a Public Offering of an amount
equal to the aggregate Warrant Price of the shares being purchased. In lieu of
exercising this Warrant as described above, the Warrantholder may elect to
receive shares equal to the value (as determined below) of this Warrant (or the
portion thereof being cancelled) by surrender of this Warrant at the principal
office of the Company together with notice of such election (which notice shall
include the number of shares being exercised hereunder), in which event the
Company shall issue to the Warrantholder a number of shares of Preferred (or
Common Stock if the Preferred has been converted into Common Stock) equal to the
quotient obtained by dividing (x) the value of the shares of Preferred being
exercised (the "Exercised Shares") on the Exercise Date, which value shall be
determined by subtracting (A) the aggregate Warrant Price of the Exercised
Shares immediately prior to the exercise of the Warrant from (B) the aggregate
fair market value of the Exercised Shares on the Exercise Date, by (y) the fair
market value of one share of Preferred (or Common Stock if the Preferred has
been converted into Common Stock) as of the Exercise Date. No fractional shares
shall be issuable upon exercise of this Warrant, and if the number of shares to
be issued determined in accordance with the foregoing formula is other than a
whole number, the Company shall pay to the holder of this Warrant an amount in
cash equal to the fair market value of the resulting fractional share on the
Exercise Date.

     The exercise of this Warrant may be made contingent upon (i) the closing of
a Public Offering, (ii) the closing of any consolidation or merger of the
Company with or into any other unaffiliated corporation, entity or person, or
any other reorganization in which the Company shall not be the continuing or
surviving entity of such consolidation, merger or reorganization (a "Merger"),
or (iii) the sale of all or substantially all of the assets of the Company (a
"Sale"). The Company shall notify the holder if an event or transaction of the
kind described in this section is proposed at least fifteen days prior to the
closing of such event or transaction; such notice shall also contain such
details of the proposed event or transaction as are reasonable in the
circumstances.

     (a) Assumption of Warrant:  If upon the closing of any Sale or Merger the
         ---------------------
successor entity assumes the obligations of this Warrant, then this Warrant
shall survive any Sale or Merger and be exercisable for the same securities,
cash, and property as would be payable for the Shares issuable upon exercise of
the unexercised portion of this Warrant as if such Shares were outstanding on
the record date for the Sale or Merger and subsequent closing. The Warrant Price
shall be adjusted accordingly.

     (b) Nonassumption:  If upon the closing of any Sale or Merger the successor
         -------------
entity does not assume the obligations of this Warrant and the Holder has not
otherwise exercised this Warrant in full, then the unexercised portion of this
Warrant shall expire upon such closing.

         Certificates for the shares issuable upon exercise of this Warrant and,
if applicable, a new warrant evidencing the balance of the shares remaining
subject to this Warrant shall be issued as of the Exercise Date and shall be
delivered to the holder within thirty days following the Exercise Date.

                                      -2-
<PAGE>

          For purposes of this Section 1, the fair market value of the Preferred
(or Common Stock if the Preferred has been converted into Common Stock) shall be
determined as follows:

          (i)   If this Warrant is exercised in connection with and contingent
upon a Public Offering, and if the Company's registration statement relating to
such Public Offering has been declared effective by the Securities and Exchange
Commission, then the fair market value shall be the initial "Price to Public"
specified in the final prospectus with respect to such offering.

          (ii)  If this Warrant is exercised in connection with any Sale or
Merger, then the fair market value per share shall be equal to the sum of all
cash, stock and other consideration received by the Company, divided by the
number of outstanding shares of the Company's capital stock (on an as-converted
into Common Stock basis) as of the closing of such transaction.

          (iii) If this Warrant is not exercised in connection with and
contingent upon a Public Offering, a Sale or Merger, then the fair market value
shall be determined by the Company's Board of Directors acting in good faith in
such fashion as is reasonable and normal for companies in a similar stage of
development.

     2.   Transfer of Warrant.  Except in accordance with the conditions
          -------------------
contained in Section 3 hereof, this Warrant and all rights hereunder are not
transferable.

     3.   Condition of Transfer or Exercise of Warrant.  It shall be a condition
          --------------------------------------------
to any transfer or exercise of this Warrant that the Company shall have
received, at the time of such transfer or exercise, a representation in writing
that this Warrant (or portion hereof transferred) or the shares of Preferred or
other securities being issued upon such exercise, as the case may be, are being
acquired for investment not with a view to any sale or distribution thereof, or
a statement of the pertinent facts covering any proposed distribution thereof.
It shall be a further condition to any transfer of this Warrant or of any or all
of the shares of Preferred issued upon exercise of this Warrant, or Common Stock
issued upon conversion of the Preferred, other than a transfer registered under
the Act, that the Company shall have received a legal opinion, in form and
substance satisfactory to the Company and its counsel, reciting the pertinent
circumstances surrounding the proposed transfer and stating that such transfer
is exempt from the prospectus and the registration requirements of the Act. The
requirement of a legal opinion shall not apply to the transfer of this Warrant
or any part thereof to a partnership of which the Warrantholder is a partner or
to the beneficial owners of such partnership without further consideration, so
long as such transfer is in compliance with applicable securities laws and the
beneficial owners are accredited investors. Each certificate evidencing the
shares of Preferred Issued upon exercise of this Warrant, or Common Stock issued
upon conversion of the Preferred, or upon any transfer of such shares (other
than a transfer registered under the Act or any subsequent transfer or shares so
registered) shall, at the option of the Company, contain a legend, in form and
substance satisfactory to the Company and its counsel, restricting the transfer
of such shares to sales or other dispositions exempt from the requirements of
the Act.

          It shall be a further condition to each such transfer of this Warrant
that the transferee shall receive and accept a Warrant, of like tenor and date,
executed by the Company.

                                      -3-
<PAGE>

     4.   Adjustment of Warrant Price and Number of Shares Purchasable
          ------------------------------------------------------------
Hereunder.  The Warrant Price and the number of shares purchasable hereunder
---------
shall be subject to adjustment from time to time in accordance with the
following provisions.

          (a)  Subdivisions or Combinations.  In case the Company shall at any
               ----------------------------
time during the Exercise Period subdivide the outstanding shares of the
Preferred, the Warrant Price in effect immediately prior to such subdivision
shall be proportionately decreased, and in case the Company shall at any time
during the Exercise Period combine the outstanding shares of the Preferred, the
Warrant Price in effect immediately prior to such combination shall be
proportionately increased, effective at the close of business on the date of
such subdivision or combination, as the case may be.

          (b)  Stock Dividends. In case the Company shall at any time during the
               ---------------
Exercise Period pay a dividend with respect to Preferred payable in Preferred,
then the Warrant Price in effect immediately prior to the record date for
distribution of such dividend shall be adjusted to that price determined by
multiplying the Warrant Price in effect immediately prior to such record date by
a fraction (i) the numerator of which shall be the total number of shares of
Preferred outstanding immediately prior to such dividend and (ii) the
denominator of which shall be the total number of shares of Preferred
outstanding immediately after such dividend.

          (c)  Number of Shares.  Upon each adjustment pursuant to subdivisions
               ----------------
(b) or (c) of this Section 4, the registered holder of this Warrant shall
thereafter (until another such adjustment) be entitled to purchase, at the
adjusted Warrant Price, the number of shares of Preferred, calculated to the
nearest full share, obtained by multiplying the number of shares of Preferred
purchasable hereunder immediately prior to such adjustment by the Warrant Price
in effect prior to such adjustment and dividing the product so obtained by the
adjusted Warrant Price.

          (d)  Reclassification.  In case of any reclassification, change or
               ----------------
conversion during the Exercise Period of securities of the class or series
issuable upon exercise of this Warrant (other than as a result of a merger,
subdivision or combination described above), or in case of any Merger where the
successor entity agrees to assume the obligations of this Warrant, the Company,
or such successor or purchasing corporation, as the case may be, shall duly
execute and deliver to the holder of this Warrant a new warrant so that the
holder of this Warrant shall have the right to receive, at a total purchase
price not to exceed that payable upon the exercise of the unexercised portion of
this Warrant, and in lieu of the shares of Preferred theretofore issuable upon
exercise of this Warrant, the kind and amount of shares of stock, other
securities, money and property receivable upon such reclassification, change or
conversion by a holder of the number of shares of Preferred then purchasable
under this Warrant. Such new warrant shall provide for adjustments that shall be
as nearly equivalent as may be practicable to the adjustments provided for in
this Section 4. The provisions of this subparagraph (d) shall similarly apply to
successive reclassifications, changes, and conversions.

          (e)  Antidilution Rights.  The antidilution rights applicable to the
               -------------------
Preferred are set forth in its Articles of Incorporation (the "Articles"), as
amended from time to time, a true and complete copy in its current form which is
attached hereto as Exhibit C. Such rights shall not be restated, amended or
modified in any manner which adversely affects the Warrantholder

                                      -4-
<PAGE>

differently than the holders of SERIES B Preferred without such Warrantholder's
prior written consent. The Company shall promptly provide the Warrantholder
hereof with any restatement, amendment or modification to the Articles promptly
after the same has been made.

     5.  Notices.
         -------

         (a)   Upon any adjustment of the Warrant Price and any increase or
decrease in the number of shares of Preferred purchasable upon the exercise of
this Warrant, then, and in each such case, the Company, within thirty (30) days
thereafter, shall give written notice thereof to the registered holder of this
Warrant at the address of such holder as shown on the books of the Company,
which notice shall state the Warrant Price as adjusted and the increased or
decreased number of shares purchasable upon the exercise of this Warrant,
setting forth in reasonable detail the method of calculation of each.

          (b)  In the event that the Company shall propose at any time to effect
an initial public offering of the Company's Common Stock pursuant to an
effective registration statement under the Act (a "Public Offering"), the
Company shall send to the Warrantholder at least fifteen days' prior written
notice of the closing date of the same; provided, however, that the failure to
give such notice shall not give the Warrantholder the right to delay or
otherwise restrain or affect the Public Offering. Such written notice may be in
lieu of the notice required under the third paragraph of Section 1 and shall be
given by first class mail, postage prepaid, addressed to the Warrantholder at
the address as shown on the books of the Company for the Warrantholder.

     6.   Registration.  The Warrantholder shall be entitled to the registration
          ------------
rights as set forth in that certain Investors' Rights Agreement dated December
18, 1997, entered into by the Company and certain Investors (the "Registration
Rights Agreement"), provided that the Warrantholder hereby agrees to be bound by
such provisions.

     7.   Representations of Warrantholder.  Concurrently with the receipt of
          --------------------------------
this Warrant and, upon exercise of this Warrant, the holder of this Warrant
shall have executed the Investment Representation Statement in the form attached
hereto as Exhibit B.

     8.   Representations and Warranties of the Company.  The Company represents
          ---------------------------------------------
and warrants to the Warrantholder, as of the Effective Date set forth below, as
follows:

          (a)  This Warrant has been duly authorized and executed by the Company
and is a valid and binding obligation of the Company, enforceable in accordance
with its terms except as to (i) the effect of applicable bankruptcy and similar
laws affecting the rights of creditors, and (ii) the effect of rules of law
governing specific performance, injunctive relief and other equitable remedies.

          (b)  The Preferred has been duly authorized and reserved for issuance
by the Company and, when issued in accordance with the terms hereof, will be
validly issued, fully paid and non-assessable, and free from all taxes, liens
and charges with respect to the issue of such shares.

                                      -5-
<PAGE>

          (c)  The rights, preference, privileges and restrictions granted to or
imposed upon the Preferred and the holders thereof are as set forth in the
Articles and the Registration Rights Agreement, a true and complete copy of
which has been delivered to the Warrantholder.

          (d)  The execution and delivery of this Warrant does not, and the
issuance of the Preferred upon exercise of this Warrant in accordance with the
terms hereof does not, conflict with the Company's Articles or Bylaws, does not
contravene any law, governmental rule or regulation, judgment or order
applicable to the Company, and does not conflict with or contravene any
provision of, or constitute a default under, any indenture, mortgage, contract
or other instrument of which the Company is a party or by which it is bound or
require the consent or approval of, the giving of notice to, the registration or
filing with or the taking of any action in respect of or by, any federal, state
or local government authority or agency or other person, other than state or
federal securities law filings.

          (e)  During the period within which this Warrant may be exercised, the
Company will at all times have authorized and reserved for the purpose of the
issue upon exercise of this Warrant a sufficient number of shares of its
Preferred to provide for the exercise of this Warrant and a sufficient number of
shares of its Common Stock to provide for the conversion of the Preferred into
Common Stock.

     9.   Miscellaneous.
          -------------

          (a)  The terms of this Warrant shall be binding upon and shall inure
to the benefit of any successors or assigns of the Company and of the holder or
holders hereof and of the Preferred issued or issuable upon the exercise hereof,
and all of the obligations of the Company relating to the Preferred issuable
upon exercise of this Warrant shall survive the exercise of this Warrant.

          (b)  No holder of this Warrant, as such, shall be entitled to vote or
receive dividends or be deemed to be a shareholder of the Company for any
purpose, nor shall anything contained in this Warrant be construed to confer
upon the holder of this Warrant, as such, any rights of a shareholder of the
Company or any right to vote, give or withhold consent to any corporate action,
receive notice of meetings, receive dividends or subscription rights, or
otherwise.

          (c)  Receipt of this Warrant by the holder hereof shall constitute
acceptance of and agreement to the foregoing terms and conditions.

          (d)  The Company will not, by amendment of its Articles of
Incorporation or through any other means, avoid or seek to avoid the observance
or performance of any of the terms of this Warrant, but will at all times in
good faith assist in the carrying out of all such terms and in the taking of all
such action as may be necessary or appropriate in order to protect the rights of
the holder of this Warrant against impairment.

          (e)  Upon receipt of evidence reasonably satisfactory to the Company
of the loss, theft, destruction or mutilation of this Warrant and, in the case
of any such loss, theft or destruction, upon delivery of an indemnity agreement
reasonably satisfactory in form and amount to the Company, or in the case of any
such mutilation, upon surrender and cancellation

                                      -6-
<PAGE>

of such Warrant, the Company at its expense will execute and deliver, in lieu
thereof, a new Warrant of like date and tenor.

          (f)  This Warrant shall be governed by the internal laws of the State
of California.

          (g)  So long as this Warrant has not terminated, the Warrantholder
shall be entitled to receive such financial information as other holders of the
same series Preferred stock.

                                      -7-
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by its
duly authorized officer.


Effective Date of Warrant: December 5, 1998

COMPANY: MOAI TECHNOLOGIES, INC.

By:/s/ Anne Perlman
   ------------------------------------
Print Name: Anne Perlman
           ----------------------------
Title President and CEO
      ---------------------------------

ACCEPTED AND AGREED:

WARRANTHOLDER: DAVID CAMPBELL


By:____________________________________

Print Name:____________________________

Title:_________________________________

                                      -8-
<PAGE>

                                   EXHIBIT A
                                   ---------

                              NOTICE OF EXERCISE



Ladies and Gentlemen:

The undersigned Warrantholder (the "Warrantholder') hereby elects to exercise
that certain SERIES B Preferred Stock Warrant (the "Warrant") by and between the
Warrantholder and ______________ (the "Company) dated ______, by surrendering
the Warrant at the principal office of the Company, in exchange for ____________
shares of SERIES B Preferred Stock of the Company (or, _____ shares of Common
Stock of the Company if such SERIES B Preferred Stock has been converted into
Common Stock).

The Warrantholder hereby confirms and acknowledges the investment
representations and warranties made in Section 7 of the Warrant, a copy of which
is available from the Company, and accepts such shares subject to the
restrictions of the Warrant.



Dated:_________________________________


WARRANTHOLDER:


_______________________________________
(Signature)

_______________________________________
(Typed or Printed Name)

_______________________________________
(Title)


Address:


_______________________________________


_______________________________________

                                      -9-
<PAGE>

                                   EXHIBIT B
                                   ---------

                      INVESTMENT REPRESENTATION STATEMENT

                             Warrants to Purchase
                       ____ Shares of SERIES B Preferred
                             Stock of ___________


     In connection with the purchase of the above-listed securities the
undersigned hereby represents to _____________________ (the "Company") as
follows:

     Receipt of Information.  The undersigned has received all the information
     ----------------------
it considers necessary or appropriate for deciding whether to purchase the
Company's SERIES B Preferred Stock issuable upon exercise of the Warrant dated
___________________ (the "Warrant") issued by the Company to the undersigned,
and it has examined any information furnished to it by the Company in connection
therewith.

     Investment Representation.
     -------------------------

     (a)  The Warrant and the shares of stock to be received by the undersigned
upon the exercise of the Warrant (the "Securities") will be acquired for
investment for its own account, not as a nominee or agent, and not with a view
to the sale or distribution of any part thereof, and the undersigned has no
present intention of selling, granting participation in or otherwise
distributing the same, but subject, nevertheless, to any requirement of law that
the disposition of its property shall at all times be within its control. By
executing this Statement, the undersigned further represents that it does not
have any contract, undertaking, agreement or arrangement with any person to
sell, transfer, or grant participations to such person or to any third person,
with respect to any Securities.

     (b)  The undersigned understands that the Securities may not be registered
under the Securities Act of 1933, as amended (the "Act"), and applicable state
securities laws, on the ground that the issuance of such Securities is exempt
pursuant to Section 4(2) of the Act and state law exemptions relating to offers
and sales not by means of a public offering, and that the Company's reliance on
such exemptions is predicated on the undersigned's representations set forth
herein. The undersigned is an "Accredited Investor" as such term is defined in
Rule 501 of the Securities and Exchange Commission.

     (c)  The undersigned agrees that in no event will it make a disposition of
any Securities unless and until (i) it shall have notified the Company of the
proposed disposition and shall have furnished the Company with a statement of
the circumstances surrounding the proposed disposition, and (ii) it shall have
furnished the Company with an opinion of counsel satisfactory to the Company and
the Company's counsel to the effect that (a) appropriate action necessary for
compliance with the Act and any applicable state securities laws has been taken
or an exemption from the registration requirements of the Act and such laws is
available, and (B) that the proposed transfer will not violate any of said laws.

                                      -10-
<PAGE>

     (d)  The undersigned represents that it is able to fend for itself in the
transactions contemplated by this Statement, has such knowledge and experience
in financial and business matters as to be capable of evaluating the merits and
risks of its investments, and has the ability to bear the economic risks
(including the risk of a total loss) of its investment. The undersigned
represents that it has had the opportunity to ask questions of the Company
concerning the Company's business and assets and to obtain any additional
information which it considered necessary to verify the accuracy of or to
amplify the Company's disclosures, and has had all questions which have been
asked by it satisfactorily answered by the Company.

     (e)  The undersigned acknowledges that the Securities must be held
indefinitely unless subsequently registered under the Act or an exemption from
such registration is available. The undersigned is aware of the provisions of
Rule 144 promulgated under the Act which permit limited resale of shares
purchased in a private placement subject to the satisfaction of certain
conditions, including, among other things, the existence of a public market for
the shares, the availability of certain current public information about the
Company, the resale occurring not less than one year after a party has purchased
and paid for the security to be sold, the sale being through a "broker's
transaction" or in transactions directly with a "market maker" (as provided by
Rule 144(f)) and the number of shares being sold during any three-month period
not exceeding specified limitations. The undersigned is aware that the
conditions for resale set forth in Rule 144 have not been satisfied.

     (f)  The undersigned represents that at no time was it presented with or
solicited by any publicly issued or circulated newspaper, mail, radio,
television or other form of general advertising or solicitation in connection
with the offer, sale and purchase of the Securities.

     (g)  The undersigned, if it is the original holder of the Warrant,
represents that it has a preexisting business or personal relationship with the
Company or any of its officers, directors or controlling persons, or by reason
of its business or financial experience or the business or financial experience
of its professional advisors who are unaffiliated with and who are not
compensated by the Company or any affiliate or selling agent of the Company,
directly or indirectly, has, and could be reasonably assumed to have, the
capacity to protect its own interests in connection with the purchase of the
Securities.


Dated:_________________________________


_______________________________________
(Signature)

_______________________________________
(Typed or Printed Name)

_______________________________________
(Title)

                                      -11-