Error in remainder of integer? (scaling offset)

Erik · 2018-03-26T16:03:26

Hi! I have a two floats (pan.x and pan.y) which allows the player to move the view in my tile-based 2d-gameworld. I also have a "float scale" for zooming the world in and out. For drawing most stuff it works fine. I just (where pos is the tile-position of something and #define TILE 20 is the size of a gametile at scale = 1): drawStuff(pos.x * scale * TILE, pos.y * scale * TILE); When I change scale it draws to the correct position on screen. But when i draw the lines that shows the grid (all the tiles) they do not offset correctly. It works when scale = 1, but when I lower scale they become off. I tried so many variations but I've got stuck. What am I doing wrong? int tile2 = TILE * scale; int offY = ((int)pan.y) % tile2; // draw horizontal lines for the grid for (int i = 0; i < h; i++) gfx.lineRelative(0, TILE*i*scale + offY, gfx.screenX, 0, col);

For Beginners C++

Started by suliman March 24, 2018 03:13 PM

11 comments, last by suliman 6 years, 8 months ago

FordPerfect

115

March 25, 2018 03:23 PM

Note, that the above "fix" can still disagree with drawStuff by 1 pixel due to the roundoff (though in rather small percentage of cases). So


for (int i = startY; i < startY + h; i++) // hori
	gfx.lineRelative(0, i * TILE*scale + pan.y, gfx.screenX, 0, col);

is probably preferred, as it should agree with drawStuff completely (assuming compiler optimizations didn't break it).

suliman

Author

1,720

March 26, 2018 04:03 PM

Yes I do the last one now, its easier.

Thanks for your help!

Error in remainder of integer? (scaling offset)

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Error in remainder of integer? (scaling offset)

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