I need to draw lines at particular slopes in two segments, where one
segment may be drawn in a different color than the continuing
segment. To draw the second segment, I use the standard formula for
slope to determine the end point of the second line segment.
Sometimes i know that point's x value in advance, sometimes its y
value. The unknown value is tagged by the constant Unknown, which is
set to an extremely high negative value.
The method calcPoint is defined as follows:
Sub calcPoint( x1 as integer, y1 as integer, x2 as integer, y2
as integer, x3 as integer, y3 as integer, ByRef x4 as integer, ByRef
y4 as integer )
I call it as follows:
(x1-x3, y1-y3 already set)
...
dim x4 as integer = Unknown
dim y4 as integer = g.Height // Bottom of the canvas in which
line will be drawn
calcPoint( x1, y1, x2, y2, x3, y3, x4, y4 )
When I trace through the program in the debugger and enter the
calcPoint method, I find that all of the parameters of calcPoint have
their correct values EXCEPT x4 and y4, which are equal to zero! What
am I doing wrong? I've never had problems with ByRef before, and
must be missing something obvious right in front of my eyes.
Thanks in advance for your help.
-Scott
Scott B. Steinman, O.D., Ph.D., F.A.A.O.
Professor, Southern College of Optometry
Chair, Open Source Purely-Graphical Programming Language Initiative
(www.ospgli.org)
Author, "Visual Programming with Prograph CPX", Manning/Prentice-
Hall, 1995 (www.manning.com/steinman).
Author, "Foundations of Binocular Vision", McGraw-Hill, 2000
(books.mcgraw-hill.com/cgi-bin/pbg/0838526705.html)
Brought to you by a grant from the Steinman Foundation (Thanks, Mom
and Dad!)
Recommended by Major University Studies Over the Leading Brand
1245 Madison Avenue
Memphis, TN 38104-2222
steinman at sco.edu
For every complex problem there is an answer that is clear, simple,
and wrong. -- H L Mencken
Nothing is impossible for the man who doesn't have to do it himself.
-- Anonymous
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