Computer Science Canada

column problem.
Author:  MossyMossy [ Tue Oct 20, 2009 7:45 pm ]
Post subject:  column problem.
here is my code so far.

Quote:


var column :int
locate (21, 1)
for count : 1..80

put "-"..
end for

loop
locate (23, 1)
put " "
locate (23, 1)

put "Choose a column for the line between 1 and 80, and with -1:"..

get column
exit when column = -1

for row : 1..20

locate (row, column)
put "+"..
end for
end loop


After doing this, I have to make it on a slant now,

I CANNOT figure out how to make a Decreasing angle, like a slant, so it go's down like " \ " instead of "|'

Please help.
Author:  copthesaint [ Wed Oct 21, 2009 12:16 am ]
Post subject:  RE:column problem.
Turing:
*deletia*


Mod Edit: Don't just give the answer. kthxbai
Author:  Zren [ Wed Oct 21, 2009 12:56 am ]
Post subject:  Re: column problem.
BASIC:
This won't make an exact line, but it'll suffice for this.
Think about what column you start, then which you'll end in. Then find the difference (delta).

end - start = difference
col6 - col4 = 2 columns apart

Then consider the fact that a straight column ( | ) has a diffence of 0. We then think about the previous column (diff of 2) and realize we'll want to stretch the line over a total of 3 column values (4, 5, 6). So we'll be breaking it down into 3 different smaller lines (or breaking it up 2 times). We want to find out the y-value where we move to the next column.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Figured it out?


ADVANCED:
If I were you, I'd try this first with Draw.Dot() before implementing it into your program. However, here's how to essentially draw a Aliased line. If you need help with how the two are relevant or any of the math, just ask.
http://www.programmersheaven.com/2/FAQ-DIRECTX-Draw-Line

Quote:
How do I draw a line?
You can use the Windows GDI to draw a line as DirectDraw doesn't provide a line drawing function. If you want to draw a line using DirectX then use Breshenham's Line Drawing Algorithm to draw lines by joining Pixels.

The pseudocode to draw a line between (x1, y1) and (x2, y2)

a) Assume x=x1 and y=y1. Plot (x, y) Pixel

b) Find the largest among (x2-x1) and (y2-y1) (To find the line is predominant on which axis)

c) If(x2-x1) is the biggest (Line is predominant on X Axis)
code:
   {   
     Loop till x becomes x2
         a. if (x2-x1) is positive then Increment x by 1
            else Decrement x by 1
         b. Find corresponding y as (int)((y2-y1)/(x2-x1))*x)
         c. Plot (x, y) Pixel
   }
   else /* The line is Predominant on Y Axis */
   {
     Loop till y becomes y2
         a. if (y2-y1) is positive then Increment y by 1
            else Decrement y by 1
         b. Find corresponding x as (int)((x2-x1)/(y2-y1))*y)
         c. Plot (x, y) Pixel
   }
Author:  MossyMossy [ Wed Oct 21, 2009 8:16 am ]
Post subject:  Re: column problem.
I've got it set for the user's input to make it for the vertical line, now i need to input it so that the user can select the row again but make it vertical.


Quote:
var column : int
locate (21, 1)

for count : 1..80
put "-"..

end for

loop
locate (23, 1)
put " "
locate (23, 1)
put "Please enter a column for the line between 1 and 80, end it with -1:"..
get column
exit when row > 25 or column > 80

locate (row, column)
put "+"..

end for
end loop



I've got the vertical line down correct, but im stuck on the mathematical problem that is here,

Quote:

var row, column:int := 1

cls

locate (21, 1)

for count : 1..80
put "-"..

end for

put "please enter a row"
get row
put "please enter column"
get column


loop
exit when row > 25

locate (column, row)

put "*" ..

row := row +1
column := column +1
end loop
Author:  Zren [ Wed Oct 21, 2009 12:42 pm ]
Post subject:  Re: column problem.
Right now you have the variables row and column. or x1,y1. Now you automatically assume that the line is going have a "width" of 25 or so (25-row actually) since that's how many times you repeat column+1. First we want to find out column and row of where we will stop (aka x2, y2).
Author:  MossyMossy [ Wed Oct 21, 2009 1:02 pm ]
Post subject:  Re: column problem.
Zren @ Wed Oct 21, 2009 12:42 pm wrote:
Right now you have the variables row and column. or x1,y1. Now you automatically assume that the line is going have a "width" of 25 or so (25-row actually) since that's how many times you repeat column+1. First we want to find out column and row of where we will stop (aka x2, y2).


now how can i find that,

make a variable called width?

then subtract the column with row?
Author:  Zren [ Wed Oct 21, 2009 2:45 pm ]
Post subject:  Re: column problem.
Turing:
slope := (y2 - y1) / (x2 - x1)

for x : x1 .. x2
    y := slope * x
end for

Slope is also usually in the form of a decimal. Also, this is for a line that is dependant on X (or Column). You need a formula that depends on Y (Rows).
hint: I've already posted the difference.

:


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