errgems1

Graphics Gems 源码 a collection of algorithms, programs, and mathematical techniques for the computer

Errata to _Graphics Gems_, first edition, edited by Andrew Glassner
([e-mail]), Academic Press 1990.  Code available online in
princeton.edu:pub/Graphics/GraphicsGems/Gems.

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

version 1.6
date:  8/25/93

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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.

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

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

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

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. 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. 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. 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).

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The following are errors in the code listings (corrected in the online code at
princeton.edu:pub/Graphics/GraphicsGems/Gems).

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 "GGems.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. 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. 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. 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 "GGems.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, bottom and p. 800, line 11:  add this pair of lines between
	"DrawBezierCurve(...);" and "return;":
	    free((void *)u);
	    free((void *)bezCurve);
p. 800, line 19:  add this pair of lines before "tHatCenter = ...":
	    free((void *)u);
	    free((void *)bezCurve);


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 "GGems.h"'
p. 700, line 5:  add '#include "GGems.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 "GGems.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 GGems.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. 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.