Rotation- How does it work??

[Builderboy]

That is because you typed it in wrong You should be using this code:

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1 2	x = (sp[c].X-xc)*cosd(d) - (sp[c].Y-yc)*sind(d) + xc; y = (sp[c].X-xc)*sind(d) + (sp[c].Y-yc)*cosd(d) + yc;

Note the plus sign instead of the minus symbol

[nxtboy III]

Yeah, I did that and added some parentheses and BOOM!!! It worked!!!! Thanks!!

[Builderboy]

Yay! Glad I could help ^^

[nxtboy III]

I tried rotating a picture by getting all the points. It works, but is really slow. Could I speed this up?

[Builderboy]

The best thing you could do would be to move the cos() and sin() outside the loop, since you really only need to calculate them once per rotation.  Just precalculate them, place them into variables of their own, and use those variables instead  

[nxtboy III]

I tried that, but for some odd reason, it messes up.

[Builderboy]

Post your code again?

[nxtboy III]

Ok.

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float magnitude(int x1,int y1,int x2,int y2) {  return(sqrt(pow(x2-x1,2) + pow(y2-y1,2))); } struct floatpoint {  float X;  float Y; }; byte Data[]; byte Line; byte offset; //LocationType poly[] = {{10,10},{ //LocationType sp[]={{10,10},{10,30},{5,27},{10,30},{15,27},{10,30},{10,25},{5,22},{10,25},{15,22},{10,25},{10,20},{5,17},{10,20},{15,17},{10,20}}; floatpoint spf[]; byte __ips_masks[] = {0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01}; byte isPixelSet(byte Xx, byte Yy) {   Line = (63-Yy & 0xF8) / 8;   offset = Yy % 8;   GetDisplayNormal(Xx, Line, 1, Data);   return Data[0] & __ips_masks[offset]; } task main() {  float x,y;  int xc,yc; // int dis;  //x=0;  //y=50;  xc= 40;  yc=40;  float deg;  int d;  //float dis[];  float c,s;  int xt1,yt1,xt2,yt2;  int l;  //int arrs = ArrayLen(sp);  int bul = 0; // ArrayInit(dis,0,arrs); // ArrayInit(spf,0,arrs); //RectOut(50,50,3,3); GraphicOut(50,40,"squirt.ric");  for(int c=0; c < 100; c++)  {   for(int d=0; d < 64; d++)   {    if(isPixelSet(c,d))    {     l++;    }   }  }  ArrayInit(spf,0,l);   for(int c=0; c < 100; c++)  {   for(int d=0; d < 64; d++)   {    if(isPixelSet(c,d))    {     spf[bul].X = c;     spf[bul].Y = d;     bul++;    }   }  }  PlayToneEx(600,30,1,0); /*   for(int c=0; c < l; c++)   {   // dis[c] = magnitude(xc,yc,sp[c].X,sp[c].Y);    //sp[c].X += 30;    //sp[c].Y += 30;    if(    spf[c].X = sp[c].X;    spf[c].Y = sp[c].Y;    }*/  while(1)  {  // x=x*(cosd(30))-y*(sind(30));   //y=x*(sind(30))+y*(cosd(30));  // x = cosd(deg--)*magnitude(0,0,x,y);  // y = sind(deg)*magnitude(0,0,x,y);  // x -= xc;   //y -= yc;   c = cosd(d);   s = sind(d);   for(int c=0; c < l; c++)   {  // deg = atan2d((sp[c].Y-yc),(sp[c].X-xc));   // xt1 = ((spf[c].X - xc) * c);    //yt1 = ((spf[c].Y - yc) * s);    //xt2 = ((spf[c].X - xc) * s);    //yt2 = ((spf[c].Y - yc) * c);    //x = (xt1 - yt1) + xc;    //y = (xt2 + yt2) + yc;   // x = sqrt(pow((spf[c].X - xc),2) + pow((spf[c].Y - yc),2))*cosd(atand(spf[c].X - xc)/(spf[c].Y - yc)+ 5)+ xc;   // y = sqrt(pow((spf[c].X - xc),2) + pow((spf[c].Y - yc),2))*sind(atand(spf[c].X - xc)/(spf[c].Y - yc)+ 5)+ yc;   //y = dis[c]*sind(deg + 3)+yc;   x = ((spf[c].X-xc)*c) - ((spf[c].Y-yc)*s) + xc;   y = ((spf[c].Y-yc)*c) + ((spf[c].X-xc)*s) + yc;   spf[c].X = x;   spf[c].Y = y;   //sp[c].X=spf[c].X;   //sp[c].Y=spf[c].Y;   }   if(ButtonPressed(BTNRIGHT,0))   d = -5;   else   d = 0;  // sp[0].X=1;   //CircleOut(x,y,10); //  PolyOut(sp); SetDisplayFlags( DISPLAY_REFRESH_DISABLED);   ClearScreen();   for(int c=0; c < l; c++)   {    PointOut(spf[c].X,spf[c].Y);   }    //PolyOut(sp);   SetDisplayFlags( DISPLAY_ON | DISPLAY_REFRESH);   Wait(17);  } }

[Builderboy]

For future reference you only have to post the relevant part of your code, not the whole thing Could it be that the issue is coming from the fact that your for loop variable is also named C?

[nxtboy III]

Wow, I can't believe I did not think of that!! Now it works.
Though it doesn't seem to go much faster.

You should help me program stuff...

[Builderboy]

Yeah rotation is slow in general without stuff like Graphics Cards :[ unfortunately I don't think you will be able to get much faster than you have it currently.

[nxtboy III]

yeah....
But you seem to be good at this language. You should help me with other stuff...

[Builderboy]

On the contrary I have little knowledge about that language, you were just lucky the issues you were having were general issues and not programming specific issues.  And if you ever have any more issues feel free to post about them and I will see what I can do ^^

[nxtboy III]

ok, sure.

[christop]

I tried rotating a picture by getting all the points. It works, but is really slow. Could I speed this up?

Are you trying to rotate a raster (bitmap) image? That's understandably going to slow because a raster image contains many points.

It might be a lot quicker to rotate it by shearing the bitmap three times: http://www.ocf.berkeley.edu/~fricke/projects/israel/paeth/rotation_by_shearing.html

Or you could try using fixed-point instead of floating-point arithmetic using your current algorithm because your system might not have floating-point hardware, so it has to be emulated in software (which is slooooow).