GMS 2 [solved] Draw border around specific grid cells

trentallain

Member
Code:
// Look for attack positions
for (var u = _begin_x; u < _end_x+1; u ++) {
    for (var v = _begin_y; v < _end_y+1; v ++) {
        // If the location is within range
        if global.grid_potential_range[# u, v] != -1 {
            // If the enemy is at that location
            if global.grid_potential_range[# u, v] == 0 {
                draw_sprite(spr_grid_hover,2,19+19*u,19+19*v);
            }
            // If there are no more spaces in range right
            if global.grid_potential_range[# u + 1, v] != -1 {
                draw_sprite_ext(spr_grid_range_border,0,19+19*u+10,19+19*v+10,1,1,0,c_white,1);
            }
            // Up
            if global.grid_potential_range[# u, v - 1] != -1 {
                draw_sprite_ext(spr_grid_range_border,0,19+19*u+10,19+19*v+10,1,1,90,c_white,1);
            }
            // Left
            if global.grid_potential_range[# u - 1, v] != -1 {
                draw_sprite_ext(spr_grid_range_border,0,19+19*u+10,19+19*v+10,1,1,180,c_white,1);
            }
            // Down
            if global.grid_potential_range[# u, v + 1] != -1 {
                draw_sprite_ext(spr_grid_range_border,0,19+19*u+10,19+19*v+10,1,1,270,c_white,1);
            }
        }
    }
}
Can someone find what is wrong with this please? What I'm trying to do is draw a sprite to create a border around grid cells that you can attack to. All works fine and looks like they are in the correct positions, however the sprite doesn't rotate as expected. The sprite is the same with as 1 grid cell, with a centered origin and the border is on the right of the sprite.

This is what it looks like (the red):
Untitledw.png
 

Simon Gust

Member
Do you want to mark all cells that are in attack range or do you want to create a border on the most-outward cells?
What result are you expecting, can you make an image that shows how you want it?

EDIT:
Also, you seem to be having a lot of magic numbers in your code.
like
Code:
19 + 19 * u + 10
and
19 + 19 * v + 10
these are oddly specific.
Why start with 19, why add 10.
Why are your cells 19x19 pixels?
 
Last edited:

trentallain

Member
278060245.png
So it should create a border like this, with the purple being the starting grid X and Y, and the yellow being an enemy in the picture.
 

trentallain

Member
Do you want to mark all cells that are in attack range or do you want to create a border on the most-outward cells?
What result are you expecting, can you make an image that shows how you want it?

EDIT:
Also, you seem to be having a lot of magic numbers in your code.
like
Code:
19 + 19 * u + 10
and
19 + 19 * v + 10
these are oddly specific.
Why start with 19, why add 10.
Why are your cells 19x19 pixels?
That's a 19 grid offset, 10 to put the origin in the centre of the cell. They are 19x19 so that it can have a 1px border.
 

Simon Gust

Member
I see.
In your code, you compare these cells against -1.
What is -1? Is it a cell that's unreachable? or a free cell?

Try reversing the logic and checking the cells equal to -1 to then draw a border.

What you can do to avoid this coordinate mess is using sub-images instead of rotation, then you can keep your sprite origin at x0 and y0.
 

trentallain

Member
I see.
In your code, you compare these cells against -1.
What is -1? Is it a cell that's unreachable? or a free cell?

Try reversing the logic and checking the cells equal to -1 to then draw a border.

What you can do to avoid this coordinate mess is using sub-images instead of rotation, then you can keep your sprite origin at x0 and y0.
-1 are the cells that aren't in range. 0 is if there is an enemy, and it is in range. 1 is if it is in range but no enemy.
 

Simon Gust

Member
Can you try this code
Code:
/*
-1 = not in range
 0 = enemy at cell
 1 = in range
*/

for (var u = _begin_x; u < _end_x+1; u++) {
for (var v = _begin_y; v < _end_y+1; v++) {
   
    // If the location is within range
    if global.grid_potential_range[# u, v] != -1 {
        // get base positions
        var xx = 19 + 19 * u;
        var yy = 19 + 19 * v;
       
        // If the enemy is at that location
        if global.grid_potential_range[# u, v] == 0 {
            draw_sprite(spr_grid_hover, 2, xx, yy);
        }
       
        // check neighbour cells
        for (n = 0; n < 4; n++) {
           
            // get cell coordinates around base cell
            var dir = n * 90;
            var uu = u + lengthdir_x(1, dir);
            var vv = v + lengthdir_y(1, dir);
           
            // check if unreachable (or enemy there) and draw border
            /*
            version with sub-images
            if (global.grid_potential_range[# uu, vv] != 1) {
                draw_sprite(spr_grid_range_border, n, xx, yy);
            }
            */
           
            // version with rotation
            if (global.grid_potential_range[# uu, vv] != 1) {
                draw_sprite_ext(spr_grid_range_border, 0, xx+10, yy+10, 1, 1, dir, c_white, 1);
            }
        }
    }
}}
 

trentallain

Member
Can you try this code
Code:
/*
-1 = not in range
 0 = enemy at cell
 1 = in range
*/

for (var u = _begin_x; u < _end_x+1; u++) {
for (var v = _begin_y; v < _end_y+1; v++) {
  
    // If the location is within range
    if global.grid_potential_range[# u, v] != -1 {
        // get base positions
        var xx = 19 + 19 * u;
        var yy = 19 + 19 * v;
      
        // If the enemy is at that location
        if global.grid_potential_range[# u, v] == 0 {
            draw_sprite(spr_grid_hover, 2, xx, yy);
        }
      
        // check neighbour cells
        for (n = 0; n < 4; n++) {
          
            // get cell coordinates around base cell
            var dir = n * 90;
            var uu = u + lengthdir_x(1, dir);
            var vv = v + lengthdir_y(1, dir);
          
            // check if unreachable (or enemy there) and draw border
            /*
            version with sub-images
            if (global.grid_potential_range[# uu, vv] != 1) {
                draw_sprite(spr_grid_range_border, n, xx, yy);
            }
            */
          
            // version with rotation
            if (global.grid_potential_range[# uu, vv] != 1) {
                draw_sprite_ext(spr_grid_range_border, 0, xx+10, yy+10, 1, 1, dir, c_white, 1);
            }
        }
    }
}}
Thanks it worked perfectly!
 

trentallain

Member
PS: To stop the out of bounds error add this line:
Code:
// Stop out of bounds error
if uu == -1 || vv == -1 || uu == _grid_w || vv == _grid_h {
    draw_sprite_ext(spr_grid_range_border, 0, xx+10, yy+10, 1, 1, dir, c_white, 1);
}
else if global.grid_potential_range[# uu, vv] != 1 {
    draw_sprite_ext(spr_grid_range_border, 0, xx+10, yy+10, 1, 1, dir, c_white, 1);
}
 
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