X-Git-Url: https://jasonwoof.com/gitweb/?p=vor.git;a=blobdiff_plain;f=sprite.c;h=447e4827525329005a673f07b098d5115227d902;hp=0a6ab871bf6c9a4baa0a64bc07fa83881d8209a5;hb=148882a3cc520f34616a1175ed157fe258d68dcc;hpb=40a38066c8a4b53017bb5f422e126dd2c6b20fd5 diff --git a/sprite.c b/sprite.c index 0a6ab87..447e482 100644 --- a/sprite.c +++ b/sprite.c @@ -115,11 +115,25 @@ add_sprite(Sprite *s) } void +reset_sprites(void) +{ + int i; + + for(i=0; itype], s); + s->flags = 0; + } +} + +void move_sprite(Sprite *s) { - // move it. - s->x += (s->dx - screendx)*t_frame; - s->y += (s->dy - screendy)*t_frame; + if(s->flags & MOVE) { + s->x += (s->dx - screendx)*t_frame; + s->y += (s->dy - screendy)*t_frame; + } } void @@ -129,7 +143,7 @@ sort_sprite(Sprite *s) if(s->x + s->w < 0 || s->x >= XSIZE || s->y + s->h < 0 || s->y >= YSIZE) { insert_sprite(&free_sprites[s->type], s); - s->type = NONE; + s->flags = 0; } else insert_sprite(square(s->x, s->y, 1-set), s); } @@ -139,7 +153,7 @@ move_sprites(void) int sq; Sprite **head; - // Move all the sprites (position and set) + // Move all the sprites for(sq=0; sqx < a->x) { Sprite *tmp = a; a = b; b = tmp; } dx = b->x - a->x; @@ -212,6 +228,28 @@ collide(Sprite *a, Sprite *b) else return mask_collide(xov, yov, a, b); } +void +collide_with_list(Sprite *s, Sprite *list) +{ + for(; list; list=list->next) + if(collide(s, list)) do_collision(s, list); +} + +void +collisions(void) +{ + int i, end = gw*gh; + Sprite *s; + for(i=0; inext) { + collide_with_list(s, s->next); + if(i+1 < end) collide_with_list(s, sprites[set][i+1]); + if(i+gw < end) collide_with_list(s, sprites[set][i+gw]); + if(i+gw+1 < end) collide_with_list(s, sprites[set][i+gw+1]); + } + } +} + Sprite * hit_in_square(Sprite *r, Sprite *s) { @@ -254,6 +292,8 @@ int pixel_collide(Sprite *s, int x, int y) { uint32_t pmask; + + if(!COLLIDES(s)) return false; if(x < s->x || y < s->y || x >= s->x + s->w || y >= s->y + s->h) return 0; @@ -262,59 +302,147 @@ pixel_collide(Sprite *s, int x, int y) return s->mask[(y*s->mask_w) + (x>>5)] & pmask; } -int +Sprite * pixel_hit_in_square(Sprite *r, float x, float y) { for(; r; r=r->next) { - if(pixel_collide(r, x, y)) return 1; + if(COLLIDES(r) && pixel_collide(r, x, y)) return r; } return 0; } -int +Sprite * pixel_collides(float x, float y) { int l, t; Sprite **sq; + Sprite *ret; l = (x + grid_size) / grid_size; t = (y + grid_size) / grid_size; sq = &sprites[set][l + t*gw]; - if(pixel_hit_in_square(*sq, x, y)) return true; - if(l > 0 && pixel_hit_in_square(*(sq-1), x, y)) return true; - if(t > 0 && pixel_hit_in_square(*(sq-gw), x, y)) return true; - if(l > 0 && t > 0 && pixel_hit_in_square(*(sq-1-gw), x, y)) return true; - return false; + if((ret = pixel_hit_in_square(*sq, x, y))) return ret; + if(l > 0 && (ret = pixel_hit_in_square(*(sq-1), x, y))) return ret; + if(t > 0 && (ret = pixel_hit_in_square(*(sq-gw), x, y))) return ret; + if(l > 0 && t > 0 && (ret = pixel_hit_in_square(*(sq-1-gw), x, y))) return ret; + return 0; } float sprite_mass(Sprite *s) { - if(s->type == SHIP_SPRITE) return s->area; - else if(s->type == ROCK_SPRITE) return 3*s->area; + if(s->type == SHIP) return s->area; + else if(s->type == ROCK) return 3 * s->area; else return 0; } +/* + * BOUNCE THEORY + * + * ****************** In 1 Dimension ***************** + * + * For now we will imagine bouncing A and B off each other in 1 dimension (along + * a line). We can safely save the other dimension for later. + * + * A and B are the same weight, and are both traveling 1m/sec, to collide right + * at the origin. With perfect bounciness, their full momentum is reversed. + * + * If we cut the weight of A down by half, then the center of our colision will + * drift towards A (the speeds of A and B are not simply reversed as in our last + * example.) However, there is always a place between A and B on the line (I'll + * call it x) such that the speeds of A and B relative to x, are simply + * reversed. Thus we can find the new speed for A like so: + * + * new A = x -(A - x) + * + * new B = x -(B - x) + * + * or, simply: + * + * new A = 2x - A + * + * new B = 2x - B + * + * + * this point x is the sort of center of momentum. If, instead of bouncing, A + * and B just globbed together, x would be center of the new glob. + * + * x is the point where there's an equal amount of force coming in from both + * sides. ie the weighted average of the speeds of A and B. + * + * average force = (A force + B force) / total mass + * + * x.speed = (a.speed * a.mass + b.speed * b.mass) / (a.mass + b.mas) + * + * then we apply the formula above for calculating the new A and B. + * + * + * + * + * ****************** In 2 Dimensions ***************** + * + * OK, that's how we do it in 1D. Now we need to deal with 2D. + * + * Imagine (or draw) the two balls just as they are bouncing off each other. + * Imagine drawing a line through the centers of the balls. The balls are + * exerting force on each other only along this axis. So if we rotate + * everything, we can do our earlier 1D math along this line. + * + * It doesn't matter what direction the balls are going in, they only exert + * force on each other along this line. What we will do is to compute the part + * of the balls' momentum that is going along this line, and bounce it according + * to our math above. The other part is unaffected by the bounce, and we can + * just leave it alone. + * + * To get this component of the balls' momentum, we can use the dot product. + * + * dot(U, V) = length(U) * length(V) * cos(angle between U and V) + * + * If U is a length 1 vector, then dot(U, V) is the length of the component of V + * in the direction of U. So the components of V are: + * + * U * dot(U, V) parallel to U + * + * V - U * dot(U, V) perpendicular to U + * + * To do the actual bounce, we compute the unit vector between the center of the + * two balls, compute the components of the balls' speeds along this vector (A + * and B), and then bounce them according to the math above: + * + * new A = 2x - A + * + * new B = 2x - B + * + * But we rewrite it in relative terms: + * + * new A = A + 2(x-A) + * + * new B = B + 2(x-B) + */ + void bounce(Sprite *a, Sprite *b) { - float x, y, n; - float va, vb; - float ma, mb, mr; + float x, y, n; // (x, y) is unit vector from a to b. + float va, vb; // va, vb are balls' speeds along (x, y) + float ma, mb; // ma, mb are the balls' masses. + float vc; // vc is the "center of momentum" // (x, y) is unit vector pointing from A's center to B's center. x = (b->x + b->w / 2) - (a->x + a->w / 2); y = (b->y + b->h / 2) - (a->y + a->h / 2); n = sqrt(x*x + y*y); x /= n; y /= n; - // velocities along (x, y), or 0 if already moving away. - va = max(x*a->dx + y*a->dy, 0); - vb = min(x*b->dx + y*b->dy, 0); + // velocities along (x, y) + va = x*a->dx + y*a->dy; + vb = x*b->dx + y*b->dy; + if(vb-va > 0) return; // don't bounce if we're already moving away. - // mass ratio + // get masses and compute "center" speed ma = sprite_mass(a); mb = sprite_mass(b); - if(ma && mb) mr = mb/ma; else mr = 1; + vc = (va*ma + vb*mb) / (ma+mb); - a->dx += x*(mb*vb - ma*va)/ma; a->dy += y*(mb*vb - ma*va)/ma; - b->dx += x*(ma*va - mb*vb)/mb; b->dy += y*(ma*va - mb*vb)/mb; + // bounce off the center speed. + a->dx += 2*x*(vc-va); a->dy += 2*y*(vc-va); + b->dx += 2*x*(vc-vb); b->dy += 2*y*(vc-vb); }