Thread: Math...

thanx guys tomorrow I'll take a deeper look into it (it's so quiet at work right now)

Code:

// Pulsing Colors Based On Text Position
	glColor3f(1.0f*float(cos(cnt1)),1.0f*float(sin(cnt2)),1.0f-0.5f*float(cos(cnt1+cnt2)));

these sort of thing just confuse me

Allright.. ive been stdying for this entire day now figuring out, and it isnt as hard as it looks thanx!!

Bubba, I am quite a newbe in graphix programming and I am very interested in that stars program you made, so I tried to make it work as much as I could but I am missing the PlotPixel function and I have no idea how to make it, if it is not very complicated and you are willing to make the function and post it here for me to include into the program, I would really appreciate it.
This is youre program with only one error:

Code:

#include <iostream>
#include <windows.h>
#include <conio.h>
using namespace std;

#define NUMSTARS 100
#define VIEWDIST 320
#define CENTER_X 160
#define CENTER_Y 100
#define WHITE 15

struct point2D
{
	int x;
	int y;
};

struct point3D
{
	double x;
	double y;
	double z;
};

struct SimpleVertex
{
	point3D Local;
	point2D Screen;
};

SimpleVertex Stars[NUMSTARS];

void CreateStars();
void MoveStars(double speed);
void ProjectStars();
void DrawStars(); 
int Random(int Limit);

void CreateStars()
{
	for (int i=0;i<NUMSTARS;i++)
	{
		Stars[i].Local.x=-320+Random(640);
		Stars[i].Local.y=-200+Random(400);
		Stars[i].Local.z=Random(100);
	}
}

void MoveStars(double speed)
{
	for (int i=0;i<NUMSTARS;i++)
	{
		Stars[i].Local.z+=speed;
		if (Stars[i].Local.z>100)
		{
			Stars[i].Local.x=-320+Random(640);
			Stars[i].Local.y=-200+Random(400);
			Stars[i].Local.z=Random(100);
		}
	}
}

void ProjectStars()
{
	for (int i=0;i<NUMSTARS;i++)
	{
		double x=Stars[i].Local.x;
		double y=Stars[i].Local.y;
		double z=Stars[i].Local.z;
     
		if (z<1.0) z=1.0; 
		Stars[i].Screen.x=(int)((x*(double)VIEWDIST)/z+(double)CENTER_X);
		Stars[i].Screen.y=(int)((y*(double)VIEWDIST)/z+(double)CENTER_Y);
	}
}

void DrawStars()
{
	for (int i=0;i<NUMSTARS;i++)
	{
		int x=Stars[i].Screen.x;
		int y=Stars[i].Screen.y; 
		if (x>0 && x<320)
		{
			if (y>0 && y<200)
			{ 
				PlotPixel(x,y,WHITE);
			}
		}
	}
}

int Random(int Limit)
{
	return (rand() % Limit + 1);
}

int main()
{
	double MySpeed=.5;
	CreateStars();

	srand(GetTickCount());

	while (!kbhit())
	{
		//Clear the screen here
		system("cls");
		MoveStars(MySpeed);
		ProjectStars();
		DrawStars();
    }
    return(0);
}

Well it looks like you are in console mode which is not going to work. If you could get a small DirectX startup module working you could plot pixels via DirectX and pointers to your double buffer and primary surfaces.

The only way in console mode is to plot periods - which looks dumb and which is reverse of graphics. Text is in row,col which is actually y,x - also the values I used in the starfield program are much too large for text mode.

For DOS users this code will complete the program. Note that I used some assembly - but you do not have to. For flipping the back buffer to the screen you could memcpy() and for clearing the screen use memset(). Please no stupid comments about the code not being portable, only for DOS, blah, blah, blah....
Because this code can be used inside of a DirectX framework as well as D3D - but in D3D would be a bit different. The DirectX version of this code only lacks the back buffer and primary surface code (locking, unlocking, etc)- as well as the startup section.

Code:

//y*320+x - most compilers should turn this into the following
#define XYTOMEM((y<<8)+(y<<6)+(x))

//BYTE typedef 
typedef unsigned char BYTE;

//Real-mode pointers to double buffer and screen
BYTE far *Screen;
BYTE far *Buffer;

//Prototypes
void Init(void);
void CLS(BYTE far *tBuffer,BYTE color);
void Flip(void);
void PlotPixel(int x,int y,BYTE color);

//Init screen mode and pointers
void Init(void)
{
   REGS regs;
   regs.x.ax=0x0013;
   int86(0x10,& regs,& regs);
   Screen=(BYTE far *)MK_FP(0xa000,0);
   Buffer=new BYTE[64000L];
   //Should check for Buffer validity here, but didn't
}

//Clears any 64000 byte buffer to the set color
void CLS(BYTE far *tBuffer,BYTE color)
{
  asm {
   
     les       di,[tBuffer]
     mov     cx,07D00h   //32000 words
     mov     ah,[color]
     mov     al,[color]
     rep      stosw
  }
}

//Copies memory - uses words, not bytes
//Copies back buffer to video memory
void Flip(void)
{
   asm {

      push      ds
      lds         si,[Buffer]
      les         di,[Screen]
      mov       cx,07D00h
      rep        movsw
      pop       ds
   }
}

//Plots a pixel - do not call this - place this in DrawStars() as is
//Calling this inside of the draw loop slows the program down  
void PlotPixel(int x,int y,BYTE color)
{
  Buffer[XYTOMEM(x,y)]=color;
}

Here is the new main:

Code:

int main(void)
{
   double MySpeed=.5;
   CreateStars();
   while (!kbhit())
   {
      CLS(Buffer,0);
      MoveStars(MySpeed);
      ProjectStars();
      DrawStars();
      Flip();
    }
    return(0);
}

Here is the new DrawStars()

Code:

void DrawStars()
{
  for (int i=0;i<NUMSTARS;i++)
  {
     int x=Stars[i].Screen.x;
     int y=Stars[i].Screen.y; 
     if (x>0 && x<320)
     {
        if (y>0 && y<200)
       { 
         Buffer[XYTOMEM(x,y)]=WHITE;
       }
     }
  }
}