errata.graphicsgems

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

            coeffs[ 0 ] = z - u;
            coeffs[ 1 ] = q < 0 ? -v : v;
            coeffs[ 2 ] = 1;

            num = SolveQuadric(coeffs, s);

            coeffs[ 0 ]= z + u;
            coeffs[ 1 ] = q < 0 ? v : -v;
            coeffs[ 2 ] = 1;

		The sign of "q" affects the sign of coeffs[1].

p. 745, throughout:  delete references to "lx", which is set but not used

p. 748, line 22:  change "negetive" to "negative"

p. 753, line 35:  change "int n1, n2," to "int n1=0, n2=0," so that first
    fprintf() error message has defined values

p. 756, line 15:  "unsigned int *fi=&f;" to
    "unsigned int *fi = (unsigned int *) &f;" for type
    consistency, and some compilers think "=&" means "&="

p. 766, top:  add '#include "GraphicsGems.h"' and '#include <math.h>'
    line 25:  change "det = det4x4( out );" to "det = det4x4( in );"
    throughout:  change "matrix4" to "Matrix4"

p. 774, line 5:  change "theta," to "theta = 0,"

p. 799, line 32: add between first "DrawBezierCurve(...);" call and "return;":
        free((void *)bezCurve);

p. 799, bottom and p. 800, line 11:  add this pair of lines between
    "DrawBezierCurve(...);" and "return;":
        free((void *)u);
        free((void *)bezCurve);
    Also, see errata note at end of this file.

p. 800, line 19:  add this pair of lines before "tHatCenter = ...":
        free((void *)u);
        free((void *)bezCurve);

p. 802, line 2: Change " < 0.0" to " < 1.0e-6" in the alpha tests.  Otherwise
    you get coincident control points that lead to divide by zero in any
    subsequent NewtonRaphsonRootFind() call.


Syntax errors (ones your compiler or lint will catch):

p. 633-642, throughout:  replace "};" with "}" to make lint happy
p. 640, gcd():  the variable "k" is set but not used - remove it

p. 649, line 31:  change "LengthVector3" to "V3Length"
p. 650, line 1:  bad end-of comment; delete "/"

p. 651, throughout:  Can't use "const" as a variable name, as it is a reserved
             word in ANSI C.  Use "liconst" instead.

p. 657, 659:  make "nicenum" declarations match, i.e. use either "double
        nicenum()" or "static double nicenum()" for both occurrences
p. 659:  change "exp" to "expv", since "exp()" is a math library function.

p. 660, line 11:  header missing end of comment "*/"

p. 662, line 13:  change "SYBYRES" to "SUBYRES"
        line 16:  bad space after "MODRES"
        line 42:  change "XRmax" to "xRmax"
p. 665, line 15:  missing semicolon after "int area"
        line 27:  change "O" to "0" in "if (partialArea>O)"
p. 666, line 13:  change "O" to "0" in "rightMask = O;"

p. 670, top:  add to make lint happy
        static scanline();
        static incrementalize_y();
        static incrementalize_x();
        static increment();
p. 671, line 35:  missing "{" at end of "while (y<ly && y<ry)"
p. 671-2, throughout:  add "(double *)" castings to all "incrementalize*"
        calls to make lint happy
p. 676, line 8:  change "if (tu<=0. ^ tv<=0.) {" to
        "if ( (tu<=0.) ^ (tv<=0.) ) {" to avoid precedence confusion
    end:  change "void pixelproc();" to "static void pixelproc();"

p. 681, throughout:  "y0" and "y1" are Bessel functions in the math library,
        so lint complains; ignore complaint or rename

p. 684:  change "delete" to "cdelete" and "insert" to "cinsert", since these
        routine names are already used by dbm database manager

p. 687, near end:  change "+ =" to "+="

p. 696, line 8:  add '#include "GraphicsGems.h"'
p. 700, line 5:  add '#include "GraphicsGems.h"'
p. 702-706:  change "max" to "MAX", "min" to "MIN"
p. 705, line 18:  delete "*sp", as it is not used
p. 706, end:  add '#include "GraphicsGems.h"'
p. 707, in clip:  delete "*sp", as it is not used
p. 709, line 23:  missing semicolon at end of "up = (up) ? FALSE : TRUE"
p. 710, top:  change "max" to "MAX", "min" to "MIN"

p. 713, line 26:  change ":" to ";" in "char **argv:"

p. 715, top:  pseudo-code at head of file (to advance from one element to the
            next) should be commented out.
        line 14:  missing declaration "int randmasks[32];"
    throughout:  three calls to "bitwidth()" need to cast argument to
        "(unsigned int)" to make lint happy

p. 719:  add "#include <string.h>" (or strings.h)

p. 727, line 11:  remove ")" in "static double bigC,..." line
p. 728, lines 21-23:  change "cal_q_msq" to "calc_q_msq"
    lines 23,42:  change "NULL" to "(double *)NULL" to make lint happy
        line 26:  change "con_const" to "cone_const" in
              "bigC = m1sq + con_const * q1"
    last line:  add a "}" to end albers_project procedure

p. 730:  missing inclusion of GraphicsGems.h.

p. 734, line 4:  change "exit();" to "exit(1);"

p. 736, line 20:  change "O" to "0" in "for (i=O;"

p. 739, line 12:  change "else if (D > 0)" to "else", since at this point
        D must be greater than 0; makes lint happy

p. 757, line 4:  change "{" to "[" in "sqrttab{"
    line 14:  change "= &n" to "= (unsigned int *)&n"
    line 21:  change "*num & = 0x7fffff:" to "*num &= 0x7fffff;" to fit
          ANSI C, and to fix error of ":" at end of line.
    line 22:  change "| =" to "|="
    line 27:  change ":" to ";"

p. 765, line 20,22:  change "Matrix" to "Matrix4"

p. 766, line 29:  change "exit();" to "exit(1);"

p. 774, line 2:  missing ";" at end of "long *argx, *argy"

p. 775:  P, Q, and M need to be declared as externs

p. 780, line 18:  bad start of comment for "/ re-parameterization"

p. 785, line 1:  bad start-of-comment

p. 789, lines 7,25:  change both "NULL" to "(Point2 *)NULL" to make lint happy
        in ConvertToBezierForm:  "t" is not used, can be deleted
p. 791, line 24:  remove "break;" after "return 0;"; unnecessary
p. 793, ControlPolygonFlatEnough:  "t" is not used, can be deleted
p. 795, ComputeXIntercept:  "T" and "Y" do not have to be computed, since
        the result "Y" is not returned.  Note that there are many
        operations in this routine that are unnecessary (e.g. "0.0 - 0.0").

p. 797-807, throughout:  change "V2ScaleII" to "V2ScaleIII" and "Bezier" to
    "BezierII" in order to avoid name collisions with the code on pages
    787-796 (i.e. the same subroutine names are used in both, but with
    different argument types, etc).  Important only if you link in both
    of these subroutine libraries.

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The following are typographical errors in the comments:

p. 687, line 3:  "plottted" to "plotted"

p. 701, line 26:  change "interscetion" to "intersection"

p. 723, line 1:  "tight" is not used in the strict mathematical sense
    that the sphere generated is optimal (i.e. no smaller sphere could be
    found), but rather meaning "near optimal".

p. 728, line 10:  "latitute" to "latitude"
p. 729, line 8:  "degress" to "degrees"

p. 724, line 38:  "seperated" to "separated"
p. 725, lines 7-9:  "componant" to "component"

p. 730, line 17:  "minium" to "minimum"

p. 752, line 2:  "positve" to "positive"

p. 760, line 5:  "interger" to "integer"
p. 761, line 4:  "preceed" to "precede"

p. 766, throughout (5 times):  "determinent" to "determinant"

p. 781, lines 7,23:  "demoninator" to "denominator"

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Addenda:  There is additional code for Kelvin Thompson's "Rendering
Anti-Aliased Lines" gem in the online distribution of the code.

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Concerning page 799, Philip Schneider's Bezier code:

If you are operating in a dimensional system such that the desired error in
the fitting process is a fraction (e.g., 0.01 inches) rather than a whole
number (e.g., 2.0 pixels), then the line on page 799 reading

iterationError = error * error;

should be changed to

iterationError = ERRFACTOR * error;

where ERRFACTOR is #defined to some implementation-dependent value such as
4.0.  If this is not done, then reparameterization will never occur.  The
result is not an erroneous curve, but a suboptimal one; the algorithm will
always subdivide when the initial fit is too "loose."

(from Earl Boebert, [e-mail])