C / C++ / MFC

17-Dec-02 18:44

Hi,

I am trying to write a simple Mandelbrot set Visual C++ program.

I assume that I am not handeling the setting the color of a pixel
correctly.

Here's some of my code ...

<br />
...<br />
void CMand_View::OnDraw(CDC* pDC)<br />
{<br />
...<br />
	for( int i=0; i<320; i++ ) {<br />
		for( int j=0; j<200; j++ ) {<br />
			int c = CMand_View::Mandel_calcColor( i, j );<br />
			pDC->SetPixel(i,j, PALETTEINDEX(c));<br />
		}<br />
	}<br />
}<br />
...<br />
double CManel_View::Mandel_Abs ( double real, double img ) {<br />
	double rc = real * real + img * img;<br />
	return sqrt( rc );<br />
}<br />
<br />
int CMand_View::Mandel_calcColor( int X, int Y ) {<br />
	<br />
	int N;         		//  WHILE-loop control variable <br />
	double XPos, YPos;	// The real and imaginary parts of C<br />
	double RealPart; 		// The real part of Z<br />
	double ImagPart; 		// The imaginary part of Z<br />
	int AbsZ;     		// BOOLEAN;<br />
	double Temp;<br />
<br />
        double width = 320.0;<br />
        double height = 200.0;<br />
<br />
	N 		= 0;<br />
	AbsZ 		= TRUE;<br />
	RealPart 	= 0;<br />
	ImagPart 	= 0;<br />
	XPos 		= X / width  * (XMax - XMin) + XMin;<br />
	YPos 		= Y / height * (YMax - YMin) + YMin;<br />
<br />
	while ( (N < Iterations) && (AbsZ == TRUE) ) {<br />
		N++;<br />
		Temp 		= (RealPart*RealPart) - (ImagPart*ImagPart) + XPos;<br />
		ImagPart 	= 2.0 * ImagPart * RealPart + YPos;<br />
		RealPart 	= Temp;<br />
		AbsZ 		= (( CMand_View::Mandel_Abs (ImagPart, RealPart) <= Bailout) ? TRUE : FALSE);<br />
	} //end while<br />
<br />
	if (AbsZ == 0 ) {<br />
		return (N + sColor) % Colors;<br />
	} else {<br />
		return 0;<br />
	}<br />
} //end calcColor<br />
<br />

I think that this ...

<br />
			pDC->SetPixel(i,j, PALETTEINDEX(c));<br />

... is not right. Confused | :confused:

Christian Graus17-Dec-02 18:50

Christian Graus

17-Dec-02 18:50

Are you using 256 colours ? Try it in a higher res. The last paremeter as an RGB value ( as returned by the RGB macro ) will work. It will be slow though. A DIBSection would give you a pixel array to set directly instead.

Christian

No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002

Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not
as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002

rbc17-Dec-02 19:00

17-Dec-02 19:00

Hi Christian,

Yes I want to use 256 colors.
How could I use the RGB macro when

<br />
int CMand_View::Mandel_calcColor( int X, int Y ) <br />

returns an int and not 3 ints?

Should I some how derieve the 3 ints (r, g, b) from c?
Where c = CMand_View::Mandel_calcColor( X, Y );

Smile | :)

Christian Graus17-Dec-02 19:36

Christian Graus

17-Dec-02 19:36

It looks like you're header for 24 bit colour and Chris has sorted it all out for you. Good luck !!!

Christian

No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002

Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not
as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002

C^hris L^osinger17-Dec-02 18:51

17-Dec-02 18:51

are you using a palette ? i don't see one.

-c

rbc17-Dec-02 18:56

17-Dec-02 18:56

That's a good question!
How do I use a palette?
I thought just using the marco ...

<br />
PALETTEINDEX(c));<br />

... would handle all that for me Laugh | :laugh:

Something is going on as my program shows
the mandelbrot set all in green! WTF | :WTF:

C^hris L^osinger17-Dec-02 18:59

17-Dec-02 18:59

the simplest way is to just come up with an array of COLORREF values:

COLORREF pal[MAXITERATIONS];
pal[0] = RGB(0,0,0);
pal[1] = RGB(64,64,0);
pal[2] = RGB(128,128,0);

...etc

then, in your loop, just use "pal[c]" instead of that PALETTEINDEX macro.

an 8-bit display is pretty rare these days. you might as well just aim for 24-bit color.

-c

rbc17-Dec-02 19:11

17-Dec-02 19:11

How should I set pal[3] through pal[255]?

Am I using a 8-bit display?
How do I use a 24-bit color?

C^hris L^osinger17-Dec-02 19:15

17-Dec-02 19:15

rbc wrote:
How should I set pal[3] through pal[255]?

pick a set of colors that looks good. in my opinion: 1. fractals work best when the palette fades between two or three colors and 2. generating the palette is as important as picking the right region to render: http://www.smalleranimals.com/thumbfrax/thumbs/_index.htm[^]

rbc wrote:
Am I using a 8-bit display?

i don't know.

rbc wrote:
How do I use a 24-bit color?

don't do anything. just render the pixels by using their COLORREF values.

-c

rbc17-Dec-02 19:21

17-Dec-02 19:21

Cool web page. You are obviously no stranger to generating
fractals! Yet I am. How would you write a mandelbrot program
in Visual C++?

Smile | :)

C^hris L^osinger17-Dec-02 19:29

17-Dec-02 19:29

rbc wrote:
How would you write a mandelbrot program
in Visual C++?

i would start by doing exactly what you're doing just to get a feel for how things work. then i would add controls to move around (zoom in/out, pan, etc.). then i would add palette creation UI (no idea what i'd do for that). then i'd add a bunch of other fractal types.

a tiny mandelbrot program[^]

#include "stdio.h"
main()
{
    int b=0,c=0,q=60,_=q;for(float i=-20,o,O=0,l=0,j,p;j=O*O,p=l*l,
    (!_--|(j+p>4)?fputc(b?q+(_/3):10,(i+=!b,p=j=O=l=0,c++,stdout)),
    _=q:l=2*O*l+i/20,O=j-p+o),b=c%q,c<2400;o=-2+b*.05);
}

-c

rbc17-Dec-02 19:44

17-Dec-02 19:44

help please!!!!!!!

jinma7817-Dec-02 18:43

jinma78

17-Dec-02 18:43

I need to program a code in which I have to return the execution time of a function in lowest time unit possible(like in millisec. or even lower) by the operating system. Can someone tell me what library call I can use in WindowsXp environment.

Thanks

Matthew
Cry | :((

Re: help please!!!!!!!

Christian Graus17-Dec-02 18:49

Christian Graus

17-Dec-02 18:49

::time is a C runtime function, declared in ctime, which should do what you want. Look up time_t in MSDN.

Christian

No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002

Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not
as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002

Re: help please!!!!!!!

C^hris L^osinger17-Dec-02 18:53

17-Dec-02 18:53

check out QueryPerformanceCounter

-c