I am trying to write my own implementation of the dividing axis theorem, but I have some problems in order for it to work as exactly as I want. I can’t say for sure, but it seems that this speaks of a collision when an imaginary box around the figures collides, as in the first form. But the second form works great.
Here are the vertex data for the square (exact coordinates):
vertsx = [ 200, 220, 220, 200 ] vertsy = [ 220, 220, 200, 200 ]
Here is the vertex data for test form 1 (relative to the mouse):
vertsx = [ -10, 0, 10, 10, -10 ] vertsy = [ -10, -50, -10, 10, 10 ]
And finally, the vertex data for test form 2 (relative to the mouse):
vertsx = [ -10, 0, 10, 10, -10 ] vertsy = [ -10, -20, -10, 10, 10 ]
For illustrative purposes only, the translated coordinates are verified, and they have forms that have been verified with the coordinates ordered as shown.
Here is the actual function.
function collisionConvexPolygon ( vertsax, vertsay, vertsbx, vertsby ) { var alen = vertsax.length; var blen = vertsbx.length; // Loop for axes in Shape A for ( var i = 0, j = alen - 1; i < alen; j = i++ ) { // Get the axis var vx = vertsax[ j ] - vertsax[ i ]; var vy = -( vertsay[ j ] - vertsay[ i ] ); var len = Math.sqrt( vx * vx + vy * vy ); vx /= len; vy /= len; // Project shape A var max0 = vertsax[ 0 ] * vx + vertsay[ 0 ] * vy, min0 = max0; for ( k = 1; k < alen; k++ ) { var proja = vertsax[ k ] * vx + vertsay[ k ] * vy; if ( proja > max0 ) { max0 = proja; } else if ( proja < min0 ) { min0 = proja; } } // Project shape B var max1 = vertsbx[ 0 ] * vx + vertsby[ 0 ] * vy, min1 = max1; for ( var k = 1; k < blen; k++ ) { var projb = vertsbx[ k ] * vx + vertsby[ k ] * vy; if ( projb > max1 ) { max1 = projb; } else if ( projb < min1 ) { min1 = projb; } } // Test for gaps if ( !axisOverlap( min0, max0, min1, max1 ) ) { return false; } } // Loop for axes in Shape B (same as above) for ( var i = 0, j = blen - 1; i < blen; j = i++ ) { var vx = vertsbx[ j ] - vertsbx[ i ]; var vy = -( vertsby[ j ] - vertsby[ i ] ); var len = Math.sqrt( vx * vx + vy * vy ); vx /= len; vy /= len; var max0 = vertsax[ 0 ] * vx + vertsay[ 0 ] * vy, min0 = max0; for ( k = 1; k < alen; k++ ) { var proja = vertsax[ k ] * vx + vertsay[ k ] * vy; if ( proja > max0 ) { max0 = proja; } else if ( proja < min0 ) { min0 = proja; } } var max1 = vertsbx[ 0 ] * vx + vertsby[ 0 ] * vy, min1 = max1; for ( var k = 1; k < blen; k++ ) { var projb = vertsbx[ k ] * vx + vertsby[ k ] * vy; if ( projb > max1 ) { max1 = projb; } else if ( projb < min1 ) { min1 = projb; } } if ( !axisOverlap( min0, max0, min1, max1 ) ) { return false; } } return true; }
I will try other forms if you need.
Here is my axisOverlap function.
function axisOverlap ( a0, a1, b0, b1 ) { return !( a0 > b1 || b0 > a1 ); }