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I am working on an isometric game engine and have already created an algorithm for pixel perfect click detection. Visit the project and notice that click detection is able to detect which edge of the tile was clicked. It is also checks the y-index to click the most upfront tile.
The isometric grid is made of tile images that are 100*65px.
TileW=100, TileL=50, tileH=15
The map is represented by a three-dimensional array map[z][y][x].
Tile center points (x,y) are calculated like so:
//x, y, z are the position of the tile
if(y%2===0) { x-=-0.5; } //To accommodate the offset found in even rows
this.centerX = (x*tileW) + (tileW/2);
this.centerY = (y*tileL) - y*((tileL)/2) + ((tileL)/2) + (tileH/2) - (z*tileH);
Prototype functions that determine if the mouse is within a given area on the tile:
Tile.prototype.allContainsMouse = function() {
var dx = Math.abs(mouse.mapX-this.centerX),
dy = Math.abs(mouse.mapY-this.centerY);
if(dx>(tileW/2)) {return false;} //Refer to image
return (dx/(tileW*0.5) + (dy/(tileL*0.5)) < (1+tileHLRatio));
}
Tile.prototype.allContainsMouse() returns true if mouse is within green. Red area is cropped out by checking if dx > half the tile's width
Tile.prototype.topContainsMouse = function() {
var topFaceCenterY = this.centerY - (tileH/2);
var dx = Math.abs(mouse.mapX-this.centerX),
dy = Math.abs(mouse.mapY-topFaceCenterY);
return ((dx/(tileW*0.5) + dy/(tileL*0.5) <= 1));
};
Tile.prototype.leftContainsMouse = function() {
var dx = mouse.mapX-this.centerX;
if(dx<0) { return true; } else { return false; }
};
(If mouse is left of the center point)
Tile.prototype.rightContainsMouse = function() {
var dx = mouse.mapX-this.centerX;
if(dx>0) { return true; } else { return false; }
};
(If mouse is right of the center point)
Bringing all the methods together to work as one:
allContainsMouse() returns true, map[z][y][x] is the tile our mouse is on.tilesUnderneathMouse array.Loop through tilesUnderneathMouse array, and choose the tile with the highest y. It is the most upfront tile.
if(allContainsMouse && !topContainsMouse)
if(allContainsMouse && !topContainsMouse && leftContainsMouse)
(Similar concept applies for right)
#1 How would you accomplish this, such that it is more efficient(not looping through all tiles)(pesudo code accepted)
#2 If you are unable to answer #1, what suggestions do you have to improve the efficiency of my click detection (chunk loading has already been considered)
I originally tried to solve this problem by not using tile center points, rather converting the mouse(x,y) position directly to the tile x,y. In my mind this is the hardest to code, yet most efficient solution. On a square grid it's very easy to convert an (x,y) position to a square on the grid. However in a staggered column grid, you deal with offsets. I tried to calculate offsets using the a function that takes an x or y value, and returns the resultant offset y, or x. The Zig-zag graph of arccos(cosx) solved that.
Checking if the mouse was within the tile, using this method was difficult and I couldn't figure it out. I was checking whether the mouse(x,y) was beneath a y=mx+b line that was dependent on the tileX, tileY approximation(a square grid approx).
If you got to here, Thanks!
328
This answer is based on:
So here it goes:
conversion between grid and screen
As I mentioned in comment you should make functions that convert between screen and cell grid positions. something like (in C++):
//---------------------------------------------------------------------------
// tile sizes
const int cxs=100;
const int cys= 50;
const int czs= 15;
const int cxs2=cxs>>1;
const int cys2=cys>>1;
// view pan (no zoom)
int pan_x=0,pan_y=0;
//---------------------------------------------------------------------------
void isometric::cell2scr(int &sx,int &sy,int cx,int cy,int cz) // grid -> screen
{
sx=pan_x+(cxs*cx)+((cy&1)*cxs2);
sy=pan_y+(cys*cy/2)-(czs*cz);
}
//---------------------------------------------------------------------------
void isometric::scr2cell(int &cx,int &cy,int &cz,int sx,int sy) // screen -> grid
{
// rough cell ground estimation (no z value yet)
cy=(2*(sy-pan_y))/cys;
cx= (sx-pan_x-((cy&1)*cxs2))/cxs;
cz=0;
// isometric tile shape crossing correction
int xx,yy;
cell2scr(xx,yy,cx,cy,cz);
xx=sx-xx; mx0=cx;
yy=sy-yy; my0=cy;
if (xx<=cxs2) { if (yy> xx *cys/cxs) { cy++; if (int(cy&1)!=0) cx--; } }
else { if (yy>(cxs-xx)*cys/cxs) { cy++; if (int(cy&1)==0) cx++; } }
}
//---------------------------------------------------------------------------
I used your layout (took mi while to convert mine to it hopefully I do not made some silly mistake somewhere):
cell2scr(x,y,0,0,0)
Beware if you are using integer arithmetics you need to take in mind if you dividing/multiplying by half sizes you can lose precision. Use full size and divide the result by 2 for such cases (spend a lot of time figuring that one out in the past).
The cell2scr is pretty straightforward. The screen position is pan offset + cell position multiplied by its size (step). The x axis need a correction for even/odd rows (that is what ((cy&1)*cxs2) is for) and y axis is shifted by the z axis (((cy&1)*cxs2)). Mine screen has point (0,0) in upper left corner, +x axis is pointing right and +y is pointing down.
The scr2cell is done by algebraically solved screen position from the equations of cell2scr while assuming z=0 so selects only the grid ground. On top of that is just the even/odd correction added if mouse position is outside found cell area.
scan neighbors
the scr2cell(x,y,z,mouse_x,mouse_y) returns just cell where your mouse is on the ground. so if you want to add your current selection functionality you need to scan the top cell on that position and few neighboring cells and select the one with least distance.
No need to scan the whole grid/map just few cells around returned position. That should speed up thing considerably.
I do it like this:
The number of lines depends on the cell z axis size (czs), max number of z layers (gzs) and the cell size (cys). The C++ code of mine with scan looks like this:
// grid size
const int gxs=15;
const int gys=30;
const int gzs=8;
// my map (all the cells)
int map[gzs][gys][gxs];
void isometric::scr2cell(int &cx,int &cy,int &cz,int sx,int sy)
{
// rough cell ground estimation (no z value yet)
cy=(2*(sy-pan_y))/cys;
cx= (sx-pan_x-((cy&1)*cxs2))/cxs;
cz=0;
// isometric tile shape crossing correction
int xx,yy;
cell2scr(xx,yy,cx,cy,cz);
xx=sx-xx;
yy=sy-yy;
if (xx<=cxs2) { if (yy> xx *cys/cxs) { cy++; if (int(cy&1)!=0) cx--; } }
else { if (yy>(cxs-xx)*cys/cxs) { cy++; if (int(cy&1)==0) cx++; } }
// scan closest neighbors
int x0=-1,y0=-1,z0=-1,a,b,i;
#define _scann \
if ((cx>=0)&&(cx<gxs)) \
if ((cy>=0)&&(cy<gys)) \
{ \
for (cz=0;(map[cz+1][cy][cx]!=_cell_type_empty)&&(cz<czs-1);cz++); \
cell2scr(xx,yy,cx,cy,cz); \
if (map[cz][cy][cx]==_cell_type_full) yy-=czs; \
xx=(sx-xx); yy=((sy-yy)*cxs)/cys; \
a=(xx+yy); b=(xx-yy); \
if ((a>=0)&&(a<=cxs)&&(b>=0)&&(b<=cxs)) \
if (cz>=z0) { x0=cx; y0=cy; z0=cz; } \
}
_scann; // scan actual cell
for (i=gzs*czs;i>=0;i-=cys) // scan as many lines bellow actual cell as needed
{
cy++; if (int(cy&1)!=0) cx--; _scann;
cx++; _scann;
cy++; if (int(cy&1)!=0) cx--; _scann;
}
cx=x0; cy=y0; cz=z0; // return remembered cell coordinate
#undef _scann
}
This selects always the top cell (highest from all the possible) when playing with mouse it feels correctly (at least to me):
Here complete VCL/C++ source for mine isometric engine I busted for this today:
//---------------------------------------------------------------------------
//--- Isometric ver: 1.01 ---------------------------------------------------
//---------------------------------------------------------------------------
#ifndef _isometric_h
#define _isometric_h
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// colors 0x00BBGGRR
DWORD col_back =0x00000000;
DWORD col_grid =0x00202020;
DWORD col_xside=0x00606060;
DWORD col_yside=0x00808080;
DWORD col_zside=0x00A0A0A0;
DWORD col_sel =0x00FFFF00;
//---------------------------------------------------------------------------
//--- configuration defines -------------------------------------------------
//---------------------------------------------------------------------------
// #define isometric_layout_1 // x axis: righ+down, y axis: left+down
// #define isometric_layout_2 // x axis: righ , y axis: left+down
//---------------------------------------------------------------------------
#define isometric_layout_2
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
/*
// grid size
const int gxs=4;
const int gys=16;
const int gzs=8;
// cell size
const int cxs=100;
const int cys= 50;
const int czs= 15;
*/
// grid size
const int gxs=15;
const int gys=30;
const int gzs=8;
// cell size
const int cxs=40;
const int cys=20;
const int czs=10;
const int cxs2=cxs>>1;
const int cys2=cys>>1;
// cell types
enum _cell_type_enum
{
_cell_type_empty=0,
_cell_type_ground,
_cell_type_full,
_cell_types
};
//---------------------------------------------------------------------------
class isometric
{
public:
// screen buffer
Graphics::TBitmap *bmp;
DWORD **pyx;
int xs,ys;
// isometric map
int map[gzs][gys][gxs];
// mouse
int mx,my,mx0,my0; // [pixel]
TShiftState sh,sh0;
int sel_x,sel_y,sel_z; // [grid]
// view
int pan_x,pan_y;
// constructors for compiler safety
isometric();
isometric(isometric& a) { *this=a; }
~isometric();
isometric* operator = (const isometric *a) { *this=*a; return this; }
isometric* operator = (const isometric &a);
// Window API
void resize(int _xs,int _ys); // [pixels]
void mouse(int x,int y,TShiftState sh); // [mouse]
void draw();
// auxiliary API
void cell2scr(int &sx,int &sy,int cx,int cy,int cz);
void scr2cell(int &cx,int &cy,int &cz,int sx,int sy);
void cell_draw(int x,int y,int tp,bool _sel=false); // [screen]
void map_random();
};
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
isometric::isometric()
{
// init screen buffers
bmp=new Graphics::TBitmap;
bmp->HandleType=bmDIB;
bmp->PixelFormat=pf32bit;
pyx=NULL; xs=0; ys=0;
resize(1,1);
// init map
int x,y,z,t;
t=_cell_type_empty;
// t=_cell_type_ground;
// t=_cell_type_full;
for (z=0;z<gzs;z++,t=_cell_type_empty)
for (y=0;y<gys;y++)
for (x=0;x<gxs;x++)
map[z][y][x]=t;
// init mouse
mx =0; my =0; sh =TShiftState();
mx0=0; my0=0; sh0=TShiftState();
sel_x=-1; sel_y=-1; sel_z=-1;
// init view
pan_x=0; pan_y=0;
}
//---------------------------------------------------------------------------
isometric::~isometric()
{
if (pyx) delete[] pyx; pyx=NULL;
if (bmp) delete bmp; bmp=NULL;
}
//---------------------------------------------------------------------------
isometric* isometric::operator = (const isometric &a)
{
resize(a.xs,a.ys);
bmp->Canvas->Draw(0,0,a.bmp);
int x,y,z;
for (z=0;z<gzs;z++)
for (y=0;y<gys;y++)
for (x=0;x<gxs;x++)
map[z][y][x]=a.map[z][y][x];
mx=a.mx; mx0=a.mx0; sel_x=a.sel_x;
my=a.my; my0=a.my0; sel_y=a.sel_y;
sh=a.sh; sh0=a.sh0; sel_z=a.sel_z;
pan_x=a.pan_x;
pan_y=a.pan_y;
return this;
}
//---------------------------------------------------------------------------
void isometric::resize(int _xs,int _ys)
{
if (_xs<1) _xs=1;
if (_ys<1) _ys=1;
if ((xs==_xs)&&(ys==_ys)) return;
bmp->SetSize(_xs,_ys);
xs=bmp->Width;
ys=bmp->Height;
if (pyx) delete pyx;
pyx=new DWORD*[ys];
for (int y=0;y<ys;y++) pyx[y]=(DWORD*) bmp->ScanLine[y];
// center view
cell2scr(pan_x,pan_y,gxs>>1,gys>>1,0);
pan_x=(xs>>1)-pan_x;
pan_y=(ys>>1)-pan_y;
}
//---------------------------------------------------------------------------
void isometric::mouse(int x,int y,TShiftState shift)
{
mx0=mx; mx=x;
my0=my; my=y;
sh0=sh; sh=shift;
scr2cell(sel_x,sel_y,sel_z,mx,my);
if ((sel_x<0)||(sel_y<0)||(sel_z<0)||(sel_x>=gxs)||(sel_y>=gys)||(sel_z>=gzs)) { sel_x=-1; sel_y=-1; sel_z=-1; }
}
//---------------------------------------------------------------------------
void isometric::draw()
{
int x,y,z,xx,yy;
// clear space
bmp->Canvas->Brush->Color=col_back;
bmp->Canvas->FillRect(TRect(0,0,xs,ys));
// grid
DWORD c0=col_zside;
col_zside=col_back;
for (y=0;y<gys;y++)
for (x=0;x<gxs;x++)
{
cell2scr(xx,yy,x,y,0);
cell_draw(xx,yy,_cell_type_ground,false);
}
col_zside=c0;
// cells
for (z=0;z<gzs;z++)
for (y=0;y<gys;y++)
for (x=0;x<gxs;x++)
{
cell2scr(xx,yy,x,y,z);
cell_draw(xx,yy,map[z][y][x],(x==sel_x)&&(y==sel_y)&&(z==sel_z));
}
// mouse0 cross
bmp->Canvas->Pen->Color=clBlue;
bmp->Canvas->MoveTo(mx0-10,my0); bmp->Canvas->LineTo(mx0+10,my0);
bmp->Canvas->MoveTo(mx0,my0-10); bmp->Canvas->LineTo(mx0,my0+10);
// mouse cross
bmp->Canvas->Pen->Color=clGreen;
bmp->Canvas->MoveTo(mx-10,my); bmp->Canvas->LineTo(mx+10,my);
bmp->Canvas->MoveTo(mx,my-10); bmp->Canvas->LineTo(mx,my+10);
// grid origin cross
bmp->Canvas->Pen->Color=clRed;
bmp->Canvas->MoveTo(pan_x-10,pan_y); bmp->Canvas->LineTo(pan_x+10,pan_y);
bmp->Canvas->MoveTo(pan_x,pan_y-10); bmp->Canvas->LineTo(pan_x,pan_y+10);
bmp->Canvas->Font->Charset=OEM_CHARSET;
bmp->Canvas->Font->Name="System";
bmp->Canvas->Font->Pitch=fpFixed;
bmp->Canvas->Font->Color=clAqua;
bmp->Canvas->Brush->Style=bsClear;
bmp->Canvas->TextOutA(5, 5,AnsiString().sprintf("Mouse: %i x %i",mx,my));
bmp->Canvas->TextOutA(5,20,AnsiString().sprintf("Select: %i x %i x %i",sel_x,sel_y,sel_z));
bmp->Canvas->Brush->Style=bsSolid;
}
//---------------------------------------------------------------------------
void isometric::cell2scr(int &sx,int &sy,int cx,int cy,int cz)
{
#ifdef isometric_layout_1
sx=pan_x+((cxs*(cx-cy))/2);
sy=pan_y+((cys*(cx+cy))/2)-(czs*cz);
#endif
#ifdef isometric_layout_2
sx=pan_x+(cxs*cx)+((cy&1)*cxs2);
sy=pan_y+(cys*cy/2)-(czs*cz);
#endif
}
//---------------------------------------------------------------------------
void isometric::scr2cell(int &cx,int &cy,int &cz,int sx,int sy)
{
int x0=-1,y0=-1,z0=-1,a,b,i,xx,yy;
#ifdef isometric_layout_1
// rough cell ground estimation (no z value yet)
// translate to (0,0,0) top left corner of the grid
xx=sx-pan_x-cxs2;
yy=sy-pan_y+cys2;
// change aspect to square cells cxs x cxs
yy=(yy*cxs)/cys;
// use the dot product with axis vectors to compute grid cell coordinates
cx=(+xx+yy)/cxs;
cy=(-xx+yy)/cxs;
cz=0;
// scan closest neighbors
#define _scann \
if ((cx>=0)&&(cx<gxs)) \
if ((cy>=0)&&(cy<gys)) \
{ \
for (cz=0;(map[cz+1][cy][cx]!=_cell_type_empty)&&(cz<czs-1);cz++); \
cell2scr(xx,yy,cx,cy,cz); \
if (map[cz][cy][cx]==_cell_type_full) yy-=czs; \
xx=(sx-xx); yy=((sy-yy)*cxs)/cys; \
a=(xx+yy); b=(xx-yy); \
if ((a>=0)&&(a<=cxs)&&(b>=0)&&(b<=cxs)) \
if (cz>=z0) { x0=cx; y0=cy; z0=cz; } \
}
_scann; // scan actual cell
for (i=gzs*czs;i>=0;i-=cys) // scan as many lines bellow actual cell as needed
{
cy++; _scann;
cx++; cy--; _scann;
cy++; _scann;
}
cx=x0; cy=y0; cz=z0; // return remembered cell coordinate
#undef _scann
#endif
#ifdef isometric_layout_2
// rough cell ground estimation (no z value yet)
cy=(2*(sy-pan_y))/cys;
cx= (sx-pan_x-((cy&1)*cxs2))/cxs;
cz=0;
// isometric tile shape crossing correction
cell2scr(xx,yy,cx,cy,cz);
xx=sx-xx;
yy=sy-yy;
if (xx<=cxs2) { if (yy> xx *cys/cxs) { cy++; if (int(cy&1)!=0) cx--; } }
else { if (yy>(cxs-xx)*cys/cxs) { cy++; if (int(cy&1)==0) cx++; } }
// scan closest neighbors
#define _scann \
if ((cx>=0)&&(cx<gxs)) \
if ((cy>=0)&&(cy<gys)) \
{ \
for (cz=0;(map[cz+1][cy][cx]!=_cell_type_empty)&&(cz<czs-1);cz++); \
cell2scr(xx,yy,cx,cy,cz); \
if (map[cz][cy][cx]==_cell_type_full) yy-=czs; \
xx=(sx-xx); yy=((sy-yy)*cxs)/cys; \
a=(xx+yy); b=(xx-yy); \
if ((a>=0)&&(a<=cxs)&&(b>=0)&&(b<=cxs)) \
if (cz>=z0) { x0=cx; y0=cy; z0=cz; } \
}
_scann; // scan actual cell
for (i=gzs*czs;i>=0;i-=cys) // scan as many lines bellow actual cell as needed
{
cy++; if (int(cy&1)!=0) cx--; _scann;
cx++; _scann;
cy++; if (int(cy&1)!=0) cx--; _scann;
}
cx=x0; cy=y0; cz=z0; // return remembered cell coordinate
#undef _scann
#endif
}
//---------------------------------------------------------------------------
void isometric::cell_draw(int x,int y,int tp,bool _sel)
{
TPoint pnt[5];
bmp->Canvas->Pen->Color=col_grid;
if (tp==_cell_type_empty)
{
if (!_sel) return;
bmp->Canvas->Pen->Color=col_sel;
pnt[0].x=x; pnt[0].y=y ;
pnt[1].x=x+cxs2; pnt[1].y=y+cys2;
pnt[2].x=x+cxs; pnt[2].y=y ;
pnt[3].x=x+cxs2; pnt[3].y=y-cys2;
pnt[4].x=x; pnt[4].y=y ;
bmp->Canvas->Polyline(pnt,4);
}
else if (tp==_cell_type_ground)
{
if (_sel) bmp->Canvas->Brush->Color=col_sel;
else bmp->Canvas->Brush->Color=col_zside;
pnt[0].x=x; pnt[0].y=y ;
pnt[1].x=x+cxs2; pnt[1].y=y+cys2;
pnt[2].x=x+cxs; pnt[2].y=y ;
pnt[3].x=x+cxs2; pnt[3].y=y-cys2;
bmp->Canvas->Polygon(pnt,3);
}
else if (tp==_cell_type_full)
{
if (_sel) bmp->Canvas->Brush->Color=col_sel;
else bmp->Canvas->Brush->Color=col_xside;
pnt[0].x=x+cxs2; pnt[0].y=y+cys2;
pnt[1].x=x+cxs; pnt[1].y=y;
pnt[2].x=x+cxs; pnt[2].y=y -czs;
pnt[3].x=x+cxs2; pnt[3].y=y+cys2-czs;
bmp->Canvas->Polygon(pnt,3);
if (_sel) bmp->Canvas->Brush->Color=col_sel;
else bmp->Canvas->Brush->Color=col_yside;
pnt[0].x=x; pnt[0].y=y;
pnt[1].x=x+cxs2; pnt[1].y=y+cys2;
pnt[2].x=x+cxs2; pnt[2].y=y+cys2-czs;
pnt[3].x=x; pnt[3].y=y -czs;
bmp->Canvas->Polygon(pnt,3);
if (_sel) bmp->Canvas->Brush->Color=col_sel;
else bmp->Canvas->Brush->Color=col_zside;
pnt[0].x=x; pnt[0].y=y -czs;
pnt[1].x=x+cxs2; pnt[1].y=y+cys2-czs;
pnt[2].x=x+cxs; pnt[2].y=y -czs;
pnt[3].x=x+cxs2; pnt[3].y=y-cys2-czs;
bmp->Canvas->Polygon(pnt,3);
}
}
//---------------------------------------------------------------------------
void isometric::map_random()
{
int i,x,y,z,x0,y0,r,h;
// clear
for (z=0;z<gzs;z++)
for (y=0;y<gys;y++)
for (x=0;x<gxs;x++)
map[z][y][x]=_cell_type_empty;
// add pseudo-random bumps
Randomize();
for (i=0;i<10;i++)
{
x0=Random(gxs);
y0=Random(gys);
r=Random((gxs+gys)>>3)+1;
h=Random(gzs);
for (z=0;(z<gzs)&&(r);z++,r--)
for (y=y0-r;y<y0+r;y++)
if ((y>=0)&&(y<gys))
for (x=x0-r;x<x0+r;x++)
if ((x>=0)&&(x<gxs))
map[z][y][x]=_cell_type_full;
}
}
//---------------------------------------------------------------------------
#endif
//---------------------------------------------------------------------------
The layout defines just the coordinate system axises directions (for yours use #define isometric_layout_2). This uses Borlands VCL Graphics::TBitmap so if you do not use Borland change it to any GDI bitmap or overwrite the gfx part to your's gfx API (it is relevant just for draw() and resize()). Also TShiftState is part of VCL it is just state of mouse buttons and special keys like shift, alt, ctrl so you can use bool or whatever else instead (currently not used as I do not have any click functionality yet).
Here my Borland window code (single form app with one timer on it) so you see how to use this:
//$$---- Form CPP ----
//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "win_main.h"
#include "isometric.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TMain *Main;
isometric iso;
//---------------------------------------------------------------------------
void TMain::draw()
{
iso.draw();
Canvas->Draw(0,0,iso.bmp);
}
//---------------------------------------------------------------------------
__fastcall TMain::TMain(TComponent* Owner) : TForm(Owner)
{
Cursor=crNone;
iso.map_random();
}
//---------------------------------------------------------------------------
void __fastcall TMain::FormResize(TObject *Sender)
{
iso.resize(ClientWidth,ClientHeight);
draw();
}
//---------------------------------------------------------------------------
void __fastcall TMain::FormPaint(TObject *Sender)
{
draw();
}
//---------------------------------------------------------------------------
void __fastcall TMain::tim_redrawTimer(TObject *Sender)
{
draw();
}
//---------------------------------------------------------------------------
void __fastcall TMain::FormMouseMove(TObject *Sender, TShiftState Shift, int X,int Y) { iso.mouse(X,Y,Shift); draw(); }
void __fastcall TMain::FormMouseDown(TObject *Sender, TMouseButton Button,TShiftState Shift, int X, int Y) { iso.mouse(X,Y,Shift); draw(); }
void __fastcall TMain::FormMouseUp(TObject *Sender, TMouseButton Button,TShiftState Shift, int X, int Y) { iso.mouse(X,Y,Shift); draw(); }
//---------------------------------------------------------------------------
void __fastcall TMain::FormDblClick(TObject *Sender)
{
iso.map_random();
}
//---------------------------------------------------------------------------
[Edit1] graphics approach
Have a look at Simple OpenGL GUI Framework User Interaction Advice?.
The main idea is to create shadow screen buffer where the id of rendered cell is stored. This provides pixel perfect sprite/cell selection in O(1) just with few lines of code.
create shadow screen buffer idx[ys][xs]
It should have the same resolution as your map view And should be capable of storing the (x,y,z) value of render cell inside single pixel (in map grid cell units). I use 32 bit pixel format so I choose 12 bits for x,y and 8 bits for z
DWORD color = (x) | (y<<12) | (z<<24)
before rendering of map clear this buffer
I use 0xFFFFFFFF as empty color so it is not colliding with cell (0,0,0).
on map cell sprite rendering
whenever you render pixel to screen buffer pyx[y][x]=color you also render pixel to shadow screen buffer idx[y][x]=c where c is encoded cell position in map grid units (see #1).
On mouse click (or whatever)
You got screen position of mouse mx,my so if it is in range just read the shadow buffer and obtain selected cell position.
c=idx[my][mx]
if (c!=0xFFFFFFFF)
{
x= c &0x00000FFF;
y=(c>>12)&0x00000FFF;
z=(c>>24)&0x000000FF;
}
else
{
// here use the grid floor cell position formula from above approach if needed
// or have empty cell rendered for z=0 with some special sprite to avoid this case.
}
With above encoding this map (screen):
is rendered also to shadow screen like this:
Selection is pixel perfect does not matter if you click on top, side...
The tiles used are:
Title: Isometric 64x64 Outside Tileset
Author: Yar
URL: http://opengameart.org/content/isometric-64x64-outside-tileset
License(s): * CC-BY 3.0 http://creativecommons.org/licenses/by/3.0/legalcode
And here Win32 Demo:
80
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