Collision detection between sprites is a common need that is currently hand-written with byte-distance checks. The climber sample has ~15 lines of collision code:
// Today: manual collision in climber
byte dx = (byte)(actor_x[0] - actor_x[ci]);
if (dx >= 248) dx = (byte)(0 - dx);
byte dyl = (byte)(actor_yy_lo[0] - actor_yy_lo[ci]);
if (dyl >= 248) dyl = (byte)(0 - dyl);
if (dx < 8 && dyl < 8)
{
// collision!
}Similar patterns appear in pong (ball vs paddle) and other game samples.
Proposed API:
// Returns true if two axis-aligned rectangles overlap
bool hit = rect_overlap(x1, y1, w1, h1, x2, y2, w2, h2);
// Simpler variant for same-size sprites:
bool hit = sprite_overlap(x1, y1, x2, y2, threshold);
This maps to a small 6502 subroutine that does unsigned subtraction + comparison on both axes. A pure neslib addition with a corresponding built-in subroutine.
Once implemented, the climber sample collision check and gap-fall detection should be updated to use this helper, along with pong's paddle/ball collision.
Related to #30
Collision detection between sprites is a common need that is currently hand-written with byte-distance checks. The climber sample has ~15 lines of collision code:
Similar patterns appear in pong (ball vs paddle) and other game samples.
Proposed API:
This maps to a small 6502 subroutine that does unsigned subtraction + comparison on both axes. A pure neslib addition with a corresponding built-in subroutine.
Once implemented, the climber sample collision check and gap-fall detection should be updated to use this helper, along with pong's paddle/ball collision.
Related to #30