errata.graphicsgems

[Game.Programming].Academic - Graphics Gems (6 books source code)

Errata to _Graphics Gems_, first edition, edited by Andrew Glassner
([e-mail]), Academic Press 1990.  Code available online at
http://www.graphicsgems.org/

compiled by Eric Haines ([e-mail]) from author and reader contributions

version 1.27
date:  7/5/2001

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Errors in the text:

p. 3, bottom:  The equation "N . P + c = 0" is better expressed as
    "N . P - c = 0" in order to match Figure 1a. [also see p. 9 errata]

p. 5, V2 Perpendicular:  change "N <- (-Vx, Vy)" to "N <- (-Vy, Vx)"

p. 5, V2 Reflect:  change "N <- (-Vy, -Vx)" to "N <- (-Vx, -Vy)"

p. 6:  change P1 and P2 lines to
    P1 <- (( -b+sqrt(d) ) / 2a) * lv + lu
    P2 <- (( -b-sqrt(d) ) / 2a) * lv + lu
    i.e. the value computed is multiplied by the direction vector and the
    line's origin is added to this new vector to get the intersection point.

p. 9-10, starting at bottom:  If the equation on p. 3 is expressed as
    "N . P - c = 0", then change all "+ c" references to "- c" and "l-sub-c"
    to "- l-sub-c".

p. 10, for "if not l-normalized", the operation in the next line should divide
    q by "( l-sub-n dot l-sub-n)", not "Length( l-sub-n )".

p. 11, bottom: change the lower bound of the sum (sigma) from i=1 to i=0.

p. 16, Product Relations. In the right hand parts of the equations the cosine
    and sine functions should be applied only to the numerator, then the
    division by 2 is done. Specifically:

        sin(a)*sin(b) = cos(a-b)/2 - cos(a+b)/2
        cos(a)*cos(b) = cos(a-b)/2 + cos(a+b)/2
        sin(a)*cos(b) = sin(a+b)/2 + sin(a-b)/2

p. 105, last sentence of first paragraph:  "ajacent" to "adjacent".

p. 216, caption for figure 2:  "54" should read "45" to be consistent with
    the figure (error in two places in caption).

p. 224, the Bit Width 23 mask is listed as 0x00400000, it should be
    0x00420000.

p. 282, 5 and 7 lines from bottom:  should read
    "then PUSH(dadRx + 1, rx, pushlx, pushrx, y-dir, -dir )"
    and
    "then PUSH(lx, dadLx-1, pushlx, pushrx, y-dir, -dir )"
    i.e. the final "dir" should be "-dir".

p. 283, 3 lines from bottom:  add an "end" above the "else begin".

p. 284, 12 lines down:  move "x <- x + 1;" to after the next "end" statement
    (move it down only one line).

p. 299, bottom: P1 and P2 as shown are actually the distances along the line
    from the line's origin (l.sub.U). Change the P1 and P2 lines to

    t1 = (-b + sqrt(d)) / 2a
    t2 = (-b - sqrt(d)) / 2a

    P1 <- l.sub.U + t1 * l.sub.V
    P2 <- l.sub.U + t2 * l.sub.V

p. 365, last line:  "Kajia" to "Kajiya".

p. 375, "revlect v" to "reflect v".

p. 395, first paragraph:  change "discussed by Haines (1989)" to "discussed by
    Haines in Glassner (1989)".

p. 406, last equation: if q is negative, the same signs should be used for the
    square root terms, i.e.

		y^2 +- y sqrt(2z - p) + z +- sqrt(z^2 - r) = 0

p. 448, last sentence of second paragraph:  change "and now nearly as simple"
    to "and not nearly as simple".

p. 463, second to last line:  change "then alpha <- alpha + pi/2" to "then
    alpha <- pi - alpha".

p. 479, Table 1: the number of Multiplies for rotation should be 16, not 12.

p. 495, equation 5:  this should have an equal sign (=) before the
    plus-or-minus (+/-).

p. 499, middle of page:  change "and i,j,K" to "and i,j,k".

p. 503, last sentence:  change "Let P' = Rot_(alpha, N) ..." to "Let P' =
    Rot_(theta, N) ...".

p. 516, last paragraph:  a reader notes an additional reference which
    predates Berger and Salmon & Slater, namely "The Viewing Transformation,"
    Technical Memo. no. 84, Alvy Ray Smith, Computer Graphics Project,
    Lucasfilm, June 24, 1983 (rev. May 4, 1984).

p. 602, second paragraph:  the matrix Tij should be:
    [ 1  0  0  0  ]
    [ 0 1/2 0  0  ]
    [ 0  0 1/4 0  ]
    [ 0  0  0 1/8 ]

p. 610:  the binomial "( n-i [over] j )" should be "( n-1 [over] j )".  This
    error appears on the fifth line of the long derivation and within the
    Zi,j definition.

p. 614:  the equation "Bi,n(t) = (1-t)Bi-1,n-1 + tBi-1,n-1(t)" should be
    "Bi,n(t) = (1-t)Bi,n-1(t) + tBi-1,n-1(t)"; the first right-hand side
    term had an incorrect subscript and was missing a "(t)".

p. 809:  the author of "Approximation of Sweep Surfaces by Tensor Product
    B-Splines" is M. (not J.) Bloomenthal.  The author is correctly
    attributed in the text (page 569).

p. 814: 5th line from bottom. "Knuth 1981" should read "Knuth 1981b" and
    "Vol. 2" should read "Vol. 1".  The reference above this should be
    "Knuth 1981a".

p. 820, 9th line from bottom:  "D.P. Greenburg" should be "D.P. Greenberg".

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The following are errors in the code listings (corrected in the online code at
http://www.graphicsgems.org/).

Serious errors (ones your compiler cannot or may not catch):

p. 630: Delete FLOOR and CEILING macros (they're more like truncations).
    Change ROUND macro to (i.e. add parentheses around "a"):
    #define ROUND(a)    ((a)>0 ? (int)((a)+0.5) : -(int)(0.5-(a)))
    Change SGN macro to (i.e. change positive condition result to "1"):
    #define SGN(a)        (((a)<0) ? -1 : 1)

p. 632:  procedure declarations for routines in the "2D and 2D Vector C
     Library" (next pages) are missing from "GraphicsGems.h", e.g.
        
        double V2SquaredLength() ;
        double V2Length() ;
        Vector2 *V2Negate() ;
        ...

p. 638, third line from bottom:  in V3Combine change last "result->y" to
    "result->z"

p. 640:  V3MulPointByMatrix() does not work.  A separate local Point3 (e.g.
    "Point3 q ;") should be used in place of "p" for assignment and then
    passed back.

p. 649, top:  add "#include <math.h>"

p. 655, top:  add the code:
		if ((px == qx) && (py == qy))
			if ((tx == px) && (ty == py)) return 2;
			else return 0;
	in order to test for the special case where the line endpoints are
	the same.

p. 656, line 23: change "return ((R->min.x * R->min.x) < Rad2);" to
    "return ((R->min.x * R->min.x + R->max.y * R->max.y) < Rad2);"

p. 662, line 10:  add "#include <math.h>"
p. 665, line 1:  change "FLOOR(...)" to "(floor((double)(...))".

p. 663, line 45:  change first "+" to "="; should read
              "VnextLeft = (Vleft=VnextLeft) + 1;"

p. 667, line 6:  change "POLY_NMAX 8" to "POLY_NMAX 10" (for triangles and
    quadrilaterals).  Six clipping planes used on convex polygons gives
    +6 potential extra vertices generated.

p. 670-673, throughout:  change "int mask" declarations to "unsigned long
    mask" declarations.  This avoids an infinite loop occuring when the
    highest bit is set.

p. 676, line 11:  add the line "up = (double *)u;"

p. 671, line 1:  add at top of page the following test (or make sure the
    Poly_vert structure has <= 32 doubles at compilation time):

    if (sizeof(Poly_vert)/sizeof(double) > 32) {
    fprintf(stderr, "Poly_vert structure too big; must be <=32 doubles\n");
    exit(1);
    }

p. 687, line 8:  Identical points cause two points to be drawn.  Between the
    first two plot() commands, add the line:

    if ( pixels_left < 0 ) return ;

p. 714, line 20:  the last "1" in "if (i + 1 < l * 1)" should be an "l"

p. 716, line 27:  missing "/" at end of comment (if not fixed, code compiles
          but is wrong)

p. 720, lines 3 and 6 from bottom:  change "m+1>>1" to "(m+1)>>1" to establish
          correct evaluation order.

p. 737, lines 19-24, from "if ((quadrant..." to "}", should read (and note
    corrected indentations on "else" statement):

                        if (coord[i] < minB[i] || coord[i] > maxB[i])
                                return (FALSE);
                } else {
                        coord[i] = candidatePlane[i];
                }

p. 742, lines 18-24 should read: