float terrain_height(terrain* ter, vec2 position) {
vec2 amount = vec2_fmod(position, 1.0);
vec2 top_left = vec2_new(floor(position.x), floor(position.y));
vec2 top_right = vec2_new(ceil(position.x), floor(position.y));
vec2 bot_left = vec2_new(floor(position.x), ceil(position.y));
vec2 bot_right = vec2_new(ceil(position.x), ceil(position.y));
top_left.x = clamp(top_left.x, 0, ter->width-1);
top_left.y = clamp(top_left.y, 0, ter->height-1);
top_right.x = clamp(top_right.x, 0, ter->width-1);
top_right.y = clamp(top_right.y, 0, ter->height-1);
bot_left.x = clamp(bot_left.x, 0, ter->width-1);
bot_left.y = clamp(bot_left.y, 0, ter->height-1);
bot_right.x = clamp(bot_right.x, 0, ter->width-1);
bot_right.y = clamp(bot_right.y, 0, ter->height-1);
float s0 = ter->heightmap[(int)top_left.x + (int)top_left.y * ter->width];
float s1 = ter->heightmap[(int)top_right.x + (int)top_right.y * ter->width];
float s2 = ter->heightmap[(int)bot_left.x + (int)bot_left.y * ter->width];
float s3 = ter->heightmap[(int)bot_right.x + (int)bot_right.y * ter->width];
return bilinear_interp(s1, s0, s3, s2, amount.x, amount.y);
}
static float perlin_noise2D(vec2 v) {
vec2 amount = vec2_fmod(v,1.0);
vec2 p1 = vec2_floor(v);
vec2 p2 = vec2_add(p1, vec2_new(1,0) );
vec2 p3 = vec2_add(p1, vec2_new(0,1) );
vec2 p4 = vec2_add(p1, vec2_new(1,1) );
int h1 = vec2_mix_hash(p1);
int h2 = vec2_mix_hash(p2);
int h3 = vec2_mix_hash(p3);
int h4 = vec2_mix_hash(p4);
double result = bismootherstep_interp(h2, h1, h4, h3, amount.x, amount.y);
return result / INT_MAX;
}
static void collision_detection() {
/*
Collision is fairly simplistic and looks something like this.
@-----@ We check for collision in those points here which
@ @ are @ signs. If any are colliding with a solid tile
| | then we shift the player so that they are no longer
@ @ colliding with it. Also invert the velocity.
@-----@
*/
character* main_char = entity_get("main_char");
const float buffer = 4;
const float bounce = 0.5;
vec2 diff;
/* Bottom Collision */
diff = vec2_fmod(main_char->position, TILE_SIZE);
vec2 bottom1 = vec2_add(main_char->position, vec2_new(buffer, TILE_SIZE));
vec2 bottom2 = vec2_add(main_char->position, vec2_new(TILE_SIZE - buffer, TILE_SIZE));
bool bottom1_col = tile_has_collision(level_tile_at(current_level, bottom1));
bool bottom2_col = tile_has_collision(level_tile_at(current_level, bottom2));
if (bottom1_col || bottom2_col) {
main_char->position = vec2_add(main_char->position, vec2_new(0,-diff.y));
main_char->velocity.y *= -bounce;
}
/* Top Collision */
diff = vec2_fmod(main_char->position, TILE_SIZE);
vec2 top1 = vec2_add(main_char->position, vec2_new(buffer, 0));
vec2 top2 = vec2_add(main_char->position, vec2_new(TILE_SIZE - buffer, 0));
bool top1_col = tile_has_collision(level_tile_at(current_level, top1));
bool top2_col = tile_has_collision(level_tile_at(current_level, top2));
if (top1_col || top2_col) {
main_char->position = vec2_add(main_char->position, vec2_new(0, TILE_SIZE - diff.y));
main_char->velocity.y *= -bounce;
}
/* Left Collision */
diff = vec2_fmod(main_char->position, TILE_SIZE);
vec2 left1 = vec2_add(main_char->position, vec2_new(0, buffer));
vec2 left2 = vec2_add(main_char->position, vec2_new(0, TILE_SIZE - buffer));
bool left1_col = tile_has_collision(level_tile_at(current_level, left1));
bool left2_col = tile_has_collision(level_tile_at(current_level, left2));
if (left1_col || left2_col) {
main_char->position = vec2_add(main_char->position, vec2_new(TILE_SIZE - diff.x,0));
main_char->velocity.x *= -bounce;
}
/* Right Collision */
diff = vec2_fmod(main_char->position, TILE_SIZE);
vec2 right1 = vec2_add(main_char->position, vec2_new(TILE_SIZE, buffer));
vec2 right2 = vec2_add(main_char->position, vec2_new(TILE_SIZE, TILE_SIZE - buffer));
bool right1_col = tile_has_collision(level_tile_at(current_level, right1));
bool right2_col = tile_has_collision(level_tile_at(current_level, right2));
if (right1_col || right2_col) {
main_char->position = vec2_add(main_char->position, vec2_new(-diff.x,0));
main_char->velocity.x *= -bounce;
}
}
