3DX TECHNOLOGIES INC, SC 13D, 1997-05-08

3DX TECHNOLOGIES INC
SC 13D, 1997-05-08
CRUDE PETROLEUM & NATURAL GAS

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<PAGE>
CUSIP NO. 88554G109
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4OMB APPROVAL
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OMB Number:. . . . . . . . . . 3235-0145
Expires: . . . . . . . .October 31, 1994
Estimated average
burden hours per form. . . . . . . 14.90
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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934
(Initial Filing)*

3DX TECHNOLOGIES
- --------------------------------------------------------------------------------
Name of Issuer

COMMON STOCK
- --------------------------------------------------------------------------------
(Title of Class of Securities)

88554G109
- --------------------------------------------------------------------------------
CUSIP Number

ROBERT C. GREENWOOD ROBERTSON, STEPHENS & COMPANY
555 CALIFORNIA STREET, SUITE 2600, SAN FRANCISCO, CA 94104
(415) 781-9700
- --------------------------------------------------------------------------------
(Name, Address and Telephone Number of Person Authorized
to Receive Notices and Communications

APRIL 2, 1997
- --------------------------------------------------------------------------------
Date of Event which Requires Filing of this Statement

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box [ ].

Check the following box if a fee is being paid with the statement [ ]. (A fee
is not required only if the reporting person: (1) has a previous statement on
file reporting beneficial ownership of more than five percent of the class of
securities described in Item 1; and (2) has filed no amendment subsequent
thereto reporting beneficial ownership of five percent or less of such class).
(See Rule 13d-7.)

NOTE: Six copies of this statement, including all exhibits, should be filed
with the Commission. See Rule 13d-1(a) for other parties to whom copies are to
be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the act
but shall be subject to all other provisions of the Act (however, see the
Notes).

<PAGE>

CUSIP NO. 88554G109
- --------------------------------------------------------------------------------
SCHEDULE 13D
- --------------------------------------------------------------------------------
CUSIP NO. 88554G109
- --------------------------------------------------------------------------------
1 NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

The Robertson Stephens Orphan Fund
Tax I.D. 94-3108651
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

WC
- --------------------------------------------------------------------------------
5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
ITEMS 2(d) OR 2(e)
/ /

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
NUMBER OF -------------------------------------------------------
SHARES 8 SHARED VOTING POWER
BENEFICIALLY 188,400
OWNED -------------------------------------------------------
BY EACH 9 SOLE DISPOSITIVE POWER
REPORTING 0
PERSON WITH -------------------------------------------------------
10 SHARED DISPOSITIVE POWER
188,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

188,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

2.6%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IV
- --------------------------------------------------------------------------------
*SEE INSTRUCTIONS BEFORE FILLING OUT! INCLUDE BOTH SIDES OF THE COVER PAGE,
RESPONSES TO ITEMS 1-7 (INCLUDING EXHIBITS) OF THE SCHEDULE, AND THE
SIGNATURE ATTESTATION

<PAGE>

Bayview Investors, LTD.
Tax I.D. 94-3108651
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

WC
- --------------------------------------------------------------------------------
5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
ITEMS 2(d) OR 2(e)
/ /

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 188,400 (includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH See Item 5.)
REPORTING -------------------------------------------------------
PERSON WITH 9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
188,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

188,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

2.6%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IV
- --------------------------------------------------------------------------------

<PAGE>

The Robertson Stephens Orphan Offshore Fund
Tax I.D.
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

WC
- --------------------------------------------------------------------------------
5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
ITEMS 2(d) OR 2(e)
/ /

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

Cayman Islands
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
NUMBER OF -------------------------------------------------------
SHARES 8 SHARED VOTING POWER
BENEFICIALLY 40,000
OWNED -------------------------------------------------------
BY EACH 9 SOLE DISPOSITIVE POWER
REPORTING 0
PERSON WITH -------------------------------------------------------
10 SHARED DISPOSITIVE POWER
40,000
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

40,000
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

.6%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

<PAGE>

The Robertson Stephens Global Natural Resources Fund
Tax I.D.
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

WC
- --------------------------------------------------------------------------------
5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
ITEMS 2(d) OR 2(e)
/ /

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

United States
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
NUMBER OF -------------------------------------------------------
SHARES 8 SHARED VOTING POWER
BENEFICIALLY 156,000
OWNED -------------------------------------------------------
BY EACH 9 SOLE DISPOSITIVE POWER
REPORTING 0
PERSON WITH -------------------------------------------------------
10 SHARED DISPOSITIVE POWER
156,000
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

156,000
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

2.2%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

<PAGE>

Robertson, Stephens & Company Investment Management L.P.
Tax I.D. 94-3181687
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

OO (Working Capital of Purchasing Funds) See Item 2.
- --------------------------------------------------------------------------------
5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
ITEMS 2(d) OR 2(e)
/ /

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON

CO
- --------------------------------------------------------------------------------

<PAGE>

Cusip No. 88554G109
- --------------------------------------------------------------------------------
SCHEDULE 13D
- --------------------------------------------------------------------------------
CUSIP NO. 88554G109
- --------------------------------------------------------------------------------
1 NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

Robertson, Stephens & Company, Incorporated
Tax I.D. 94-3172874 See Exhibit A for a list of Executive Officers
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON

CO
- --------------------------------------------------------------------------------

<PAGE>

Paul Stephens
Tax I.D. ###-##-####
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

WC & PF
- --------------------------------------------------------------------------------
5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
ITEMS 2(d) OR 2(e)
/ /

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

UNITED STATES
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IN
- --------------------------------------------------------------------------------
<PAGE>

Sanford Robertson
Tax I.D. ###-##-####
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IN
- --------------------------------------------------------------------------------

<PAGE>

Michael G. McCaffery
Tax I.D. ###-##-####
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IN
- --------------------------------------------------------------------------------

<PAGE>

G. Randy Hecht
Tax I.D. ###-##-####
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IN
- --------------------------------------------------------------------------------

<PAGE>

Kenneth R. Fitzsimmons
Tax I.D. ###-##-####
- --------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)/ /
(b)/X/
- --------------------------------------------------------------------------------
3 SEC USE ONLY

- --------------------------------------------------------------------------------
4 SOURCE OF FUNDS*

- --------------------------------------------------------------------------------
6 CITIZENSHIP OR PLACE OF ORGANIZATION

CALIFORNIA
- --------------------------------------------------------------------------------
7 SOLE VOTING POWER
0
-------------------------------------------------------
8 SHARED VOTING POWER
NUMBER OF 384,400 includes shares held of record by The
SHARES Robertson Stephens Orphan Fund of which Robertson,
BENEFICIALLY Stephens & Co. Investment Management, L.P. and
OWNED Bayview Investors, Ltd. are the General Partners.
BY EACH Includes shares held of record by The Robertson
REPORTING Stephens Orphan Offshore Fund of which Robertson,
PERSON WITH Stephens & Co. Investment Management, L.P. is the
General Partner. Included shares held of record
by the Robertson Stephens Global Natural Resources
Fund of which Robertson Stephens & Co Investment
Management L.P. is investment adviser.
See Item 5.)
-------------------------------------------------------
9 SOLE DISPOSITIVE POWER
0
-------------------------------------------------------
10 SHARED DISPOSITIVE POWER
384,400
- --------------------------------------------------------------------------------
11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

384,400
- --------------------------------------------------------------------------------
12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
/ /

- --------------------------------------------------------------------------------
13 PERCENT OF CLASS REPRESENT BY AMOUNT IN ROW (11)

5.3%
- --------------------------------------------------------------------------------
14 TYPE OF REPORTING PERSON*

IN
- --------------------------------------------------------------------------------
*SEE INSTRUCTIONS BEFORE FILLING OUT! INCLUDE BOTH SIDES OF THE COVER PAGE,
RESPONSES TO ITEMS 1-7 (INCLUDING EXHIBITS) OF THE SCHEDULE, AND THE SIGNATURE
ATTESTATION

<PAGE>

Cusip No. 88554G109

ITEM 1. SECURITY AND ISSUER.

This Schedule 13D is filed with respect to the Common Stock of 3DX
Technologies, Inc. (The "Company") whose principal offices are located at 12012
Wickchester, Suite 250, Houston, TX 77079-1208.

ITEM 2: IDENTITY AND BACKGROUND.

The Schedule 13D is filed on behalf of The Robertson Stephens Orphan Fund,
Robertson, Stephens & Company Investment Management, L.P. ("RS&Co.,L.P."),
Bayview Investors, Ltd. ("Bayview"), The Robertson Stephens Orphan Offshore
Fund, Robertson, Stephens & Company, Inc. ("RS&Co., Inc."), The Robertson
Stephens Global Natural Resources Fund and RS&Co., Inc.'s five shareholders,
Messrs. Sanford R. Robertson, Paul H. Stephens, Michael G. McCaffery, G. Randy
Hecht, and Kenneth R. Fitzsimmons. The purchase of the Company's shares giving
rise to this 13D was made by three investment funds, The Robertson Stephens
Orphan Fund, The Robertson Stephens Orphan Offshore Fund and the Robertson
Stephens Global Natural Resources Fund.

This Schedule 13D relates to the direct beneficial ownership in the shares
of the Company by the Funds, and the indirect beneficial ownership of RS&Co.,
L.P., Bayview, and RS&Co., Inc. in the shares of the Company held by the Funds.
Messrs. Robertson, Stephens, McCaffery, Hecht and Fitzsimmons disclaim any
beneficial ownership with respect to shares of the Company that RS&Co., Inc. may
be deemed to be beneficially own, are included in this Schedule 13D for
protective disclosure purposes only, and shall not be deemed by their inclusion
in this Schedule 13D to have made any admission that any such person has any
beneficial interest in such shares.

Set forth below is the following information with respect to the persons
signing this Schedule 13D: name; place of organization; address of principal
business and office; principal business; information concerning criminal
convictions during the past five years; and information concerning civil or
administrative proceedings during the past five years with respect to any state
or federal securities laws.

I. (a) The Robertson Stephens Orphan Fund, L.P., is a California limited
partnership. Robertson Stephens & Co. Investment Management L.P.
and Bayview Investors LTD. are the General Partners.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

II. (a) The Robertson Stephens Orphan Offshore Fund is a Cayman Islands
limited partnership. Robertson, Stephens & Co Investment Management
L.P. is the General Partner.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

<PAGE>

Cusip No. 88554G109

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

III. (a) Robertson Stephens Global Natural Resources Fund, A Massachusetts
Business Trust. The Registered Investment Manager of The Robertson
Stephens Global Natural Resources Fund is: Robertson, Stephens & Co.
Investment Management, L.P. The General Partner of Robertson,
Stephens & Co. Investment Management, L.P. is Robertson, Stephens &
Company, Incorporated.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

IV. (a) Bayview Investors LTD., is a California limited partnership.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

V. (a) Robertson, Stephens & Company, Incorporated, is a California
Corporation. Robertson, Stephens & Company, Incorporated is the
General Partner of Robertson, Stephens & Company Investment
Management, L.P.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

VI. (a) Paul H. Stephens.

<PAGE>

Cusip No. 88554G109

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(c) Paul H. Stephens is Managing Director and Chief Investment Officer,
and a shareholder, of Robertson, Stephens & Company, Incorporated.

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

VII. (a) Sanford R. Robertson.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

VIII. (a) Michael G. McCaffery.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(c) Michael G. McCaffery is the President and Chief Executive Officer,
and a shareholder, of Robertson, Stephens & Company, Incorporated.

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

IX. (a) G. Randy Hecht.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(c) G. Randy Hecht is the Executive Vice President, Chief Operating
Officer, and shareholder of Robertson, Stephens & Company,
Incorporated.

<PAGE>

Cusip No. 88554G109

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

X. (a) Kenneth R. Fitzsimmons.

(b) 555 California Street, Suite 2600
San Francisco, CA 94104

(c) Kenneth R. Fitzsimmons is the Managing Director, Director of Capital
Markets, and shareholder of Robertson, Stephens & Company,
Incorporated.

(d) No convictions in criminal proceedings.

(e) No civil or administrative proceedings.

ITEM 3: SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION:

The securities with respect to which this Schedule 13D is filed were
purchased by the Funds using working capital contributed by their respective
partners and shareholders.

ITEM 4: PURPOSE OF TRANSACTION:

The securities with respect to which this Schedule 13D is filed were
purchased by the Funds in the ordinary course of investment and not with the
intention nor effect of changing or influencing control of the Issuer. The
reporting persons may sell all or part or acquire additional securities of the
Issuer depending on market conditions and other economic factors.

ITEM 5: INTEREST IN SECURITIES OF THE ISSUER.

(a) (b) The aggregate number and percentage of the class of
securities identified pursuant to Item 1 of this Schedule 13D that are
beneficially owned by the persons listed in Item 2 are as follows:

No. of Shares
Name of Beneficially Percentage of
Beneficial Owner Owned Class(1)
----------------------------------------------------------------------------------------
<S> <C> <C>
The Robertson Stephens Orphan Fund 188,400 (2) 2.6%
The Robertson Stephens Orphan Offshore Fund 40,000 (3) .6%
The Robertson Stephens Global Natural Resources Fund 156,000 (4) 2.2%
Robertson Stephens & Co Investment Mngmnt L.P. 384,400 (5) 5.3%
Bayview Investors LTD 188,400 (6) 2.6%
Robertson Stephens & Co. Incorporated 384,400 (7) 5.3%
Paul H. Stephens 384,400 (8) 5.3%
Sanford R. Robertson 384,400 (9) 5.3%
Michael G. McCaffery 384,400 (10) 5.3%
G. Randy Hecht 384,400 (11) 5.3%
Kenneth R. Fitzsimmons 384,400 (12) 5.3%
</TABLE>

<PAGE>

Cusip No. 88554G109

(1) All percentages in this table are based, pursuant to Rule 13D-1(e) of the
Securities Exchange Act of 1934, as amended, on 7,216,177 shares of Common
Stock of the Issuer outstanding as of April 19, 1997.

(2) The Robertson Stephens Orphan Fund is a California limited partnership.

(3) The Orphan Offshore Fund is a Cayman Islands limited partnership.

(4) The Robertson Stephens Global Natural Resources Fund is a registered
investment company. Robertson, Stephens & Co. Investment Management L.P. is
the registered investment manager for the Global Natural Resources Fund.
RS&Co., Inc. is the General Partner of Robertson Stephens & Co. Investment
Management L.P.

(5) Robertson, Stephens & Co.Investment Management L.P., a California Limited
Partnership, as General Partner of The Robertson Stephens Orphan Fund and
the Orphan Offshore Fund, and is deemed to have shared dispositive power
over 384,400 shares of the Company.

(6) Bayview Investors, Ltd. is a California Limited Partnership, and as General
Partner of The Robertson Stephens Orphan Fund and is deemed to have shared
dispositive power over 188,400 shares of the Company.

(7) Robertson, Stephens & Company, Inc., a California Corporation, is the
General Partner of Robertson, Stephens & Company Investment Management
L.P., and as such is deemed to have shared dispositive power over 384,400
shares of the Company.

(8) Paul H. Stephens is the Chief Investment Officer of RS&Co., Inc. and as
such may be deemed to have shared voting power over 384,400 shares of the
Company. He is also a shareholder of Robertson, Stephens & Company Inc.

(9) Sanford R. Robertson is Chairman and a shareholder of Robertson, Stephens &
Company Inc. and as such may be deemed to have shared voting power over
384,400 shares of the Company held by the Funds.

(10) Michael G. McCaffery is President and Chief Executive Officer and a
shareholder of Robertson, Stephens & Company Inc. and as such may be deemed
to have shared voting power over 384,400 shares of the Company held by the
Funds.

(11) G. Randy Hecht is Executive Vice President, Chief Operating Officer and a
shareholder of Robertson, Stephens & Company Inc. and as such may be deemed
to have shared voting power over 384,400 shares of the Company held by the
Funds.

(12) Kenneth R. Fitzsimmons is the Managing Director, Director of Capital
Markets and a shareholder of Robertson, Stephens & Company Inc. and as such
may be deemed to have shared voting power over 384,400 shares of the
Company held by the Funds.

<PAGE>

Cusip No. 88554G109

Entity Date Shares Price Transaction
------ ---- ------ ----- -----------

Global Natural Resources 4/2/97 50,000 8.13 open mkt purchase

Global Natural Resources 4/2/97 6,000 8.25 open mkt purchase

Orphan Fund 4/2/97 50,000 8.13 open mkt purchase

Orphan Fund 4/2/97 4,000 8.25 open mkt purchase

Orphan Fund 4/2/97 21,000 8.70 open mkt purchase

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
TO SECURITIES OF THE ISSUER.

Please refer to Item 5.

ITEM 7. MATERIAL TO BE FILED AS EXHIBITS.

The following exhibits are filed herewith:

Exhibit A - Agreement of Joint Filing

<PAGE>

Cusip No. 88554G109

ITEM 8. SIGNATURE PAGE.

After reasonable inquiry and to the best of my knowledge and belief,
the undersigned certify that the information set forth in this statement is
true, complete and correct.

Dated: May 7, 1997

THE ROBERTSON STEPHENS ORPHAN FUND, A CALIFORNIA LIMITED
PARTNERSHIP.
By Robertson, Stephens & Company, L.P.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

THE ROBERTSON STEPHENS GLOBAL NATURAL RESOURCES FUND, A REGISTERED
INVESTMENT COMPANY
By Robertson, Stephens & Company, L.P.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

BAYVIEW INVESTORS, LTD., A CALIFORNIA LIMITED PARTNERSHIP.
By Robertson, Stephens & Company, L.P.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

ROBERTSON, STEPHENS & COMPANY, L.P., A CALIFORNIA LIMITED PARTNERSHIP.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

ROBERTSON, STEPHENS & COMPANY, INCORPORATED

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

<PAGE>

Cusip No. 88554G109

Paul H. Stephens*
-----------------
Paul H. Stephens

Sanford R. Robertson*
---------------------
Sanford R. Robertson

Michael G. McCaffery*
---------------------
Michael G. McCaffery

G. Randy Hecht*
---------------
G. Randy Hecht

Kenneth R. Fitzsimmons*
-----------------------
Kenneth R. Fitzsimmons

*By:
-----------------------------
Robert C. Greenwood
Pursuant to Power of Attorney
Previously Filed

<PAGE>

Cusip No. 88554G109

EXHIBIT A

AGREEMENT OF JOINT FILING

The undersigned hereby agree that they are filing jointly pursuant to
Rule 13d-1(f)(1) of the Act of the Statement dated January 31, 1997 containing
the information required by Schedule 13D, for the Common Stock of CD Radio, Inc.
held by The Robertson Stephens Orphan Fund, Bayview Investors, Ltd., Robertson,
Stephens & Company, Investment Management L.P., and Robertson, Stephens &
Company, Incorporated.

Dated: May 7, 1997

THE ROBERTSON STEPHENS ORPHAN FUND, A CALIFORNIA LIMITED PARTNERSHIP.
By Robertson, Stephens & Company, L.P.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

THE ROBERTSON STEPHENS ORPHAN OFFSHORE FUND, A CAYMAN ISLANDS LIMITED
PARTNERSHIP.
By Robertson, Stephens & Company, L.P.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

BAYVIEW INVESTORS, LTD., A CALIFORNIA LIMITED PARTNERSHIP.
By Robertson, Stephens & Company, L.P.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

ROBERTSON, STEPHENS & COMPANY INVESTMENT MANAGEMENT, L.P., A
CALIFORNIA LIMITED PARTNERSHIP.
By Robertson, Stephens & Company, Incorporated

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

<PAGE>

Cusip No. 88554G109

ROBERTSON, STEPHENS & COMPANY, INCORPORATED

By: Paul H. Stephens*
-----------------
Paul H. Stephens
Managing Director and Chief Investment Officer

Paul H. Stephens*
-----------------
Paul H. Stephens

Sanford R. Robertson*
---------------------
Sanford R. Robertson

Michael G. McCaffery*
---------------------
Michael G. McCaffery

G. Randy Hecht*
---------------
G. Randy Hecht

Kenneth R. Fitzsimmons*
-----------------------
Kenneth R. Fitzsimmons

*By
-----------------------------
Robert C. Greenwood
Pursuant to Power of Attorney
Previously Filed