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QuestionFind X,Y index into 2D array/matrix using an angle and number of cells Pin
imk12326-Mar-23 7:37
imk12326-Mar-23 7:37 
Hello,
I am working on a robots projects and part of this project is a local map space (2D array/matrix).
This map consists of 201 x 201 1cm squares, with the robot sitting in the middle.
From a robots point of view this local map has a index range of -100x -100y to +100x +100y
With the robot sitting at cell 0,0, obviously from a c/c++ point of view.
The array/matrix is addressed from 0x to 200x and 0y to 200y. (0x,0y being array/matrix bottom left)
I have successfully implement a robot rolling road and robot array/matrix rotations.
However, for some reason my brain has gone into gimble lock.
Trying to figure how to find the array/matrix x,y indices for a number of cells at a given angle from the middle of the map (robots position).
The code below produces perfect result for 100 cells at 0,45,90,135,180,225,270,315 degrees but at other angle is fails, can someone help please.
Many thanks in advance imk

#define LOCAL_MAP_NUM_X_CELLS 201
#define LOCAL_MAP_NUM_Y_CELLS 201
#define DEG_TO_RAD 0.0174533

struct LocalMap
{
unsigned char Cell[ LOCAL_MAP_NUM_Y_CELLS ][ LOCAL_MAP_NUM_X_CELLS ];
}; typedef struct LocalMap LocalMap;

int Cell_X;
int Cell_Y;

ComputeLocalMapCellIntexFromCentre( 315 , 100 , &Cell_X , &Cell_Y );

int ComputeLocalMapCellIntexFromCentre( double Angle , int NumberCells , int *pCell_X , int *pCell_Y )
{
double AngleAdjustMent;
double Sin = sin( Angle * DEG_TO_RAD);
double Cos = cos( Angle * DEG_TO_RAD);
double NumCells;

AngleAdjustMent = ( fabs( sin( Angle * DEG_TO_RAD)) + fabs( cos( Angle * DEG_TO_RAD )) );

NumCells = (double)NumberCells;
NumCells = round( (double)NumCells * AngleAdjustMent );

NumberCells = (int)NumCells;

*pCell_X = (int)round( Sin * NumberCells ) + ( LOCAL_MAP_NUM_X_CELLS - 1 ) / 2;
*pCell_Y = (int)round( Cos * NumberCells ) + ( LOCAL_MAP_NUM_Y_CELLS - 1 ) / 2;

return( TRUE );
}

modified 26-Mar-23 13:43pm.

AnswerRe: Find X,Y index into 2D array/matrix using an angle and number of cells Pin
Mircea Neacsu26-Mar-23 8:04
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AnswerRe: Find X,Y index into 2D array/matrix using an angle and number of cells Pin
Gerry Schmitz26-Mar-23 8:50
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