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#version 330
#if defined VERTEX_SHADER
layout (location = 0) in vec2 in_position;
layout (location = 1) in vec2 in_velocity;
out vec2 out_position;
out vec2 out_velocity;
uniform float timedelta;
uniform sampler2D data;
uniform int num_boids;
uniform int tex_width;
const float MAX_SPEED = 0.1;
ivec2 texelPos(int i) {
return ivec2(i % tex_width, i / num_boids);
}
void read_boid(out vec2 pos, out vec2 vel, int i) {
pos = texelFetch(data, texelPos(i), 0).rg;
vel = texelFetch(data, texelPos(i + 1), 0).rg;
}
void main() {
vec2 tmp_pos = vec2(0.0);
vec2 tmp_vel = vec2(0.0);
vec2 boid_co = vec2(0.0);
vec2 boid_se = vec2(0.0);
vec2 boid_vel = vec2(0.0);
int count = 0;
for (int i = 0; i < num_boids; i++) {
if (i == gl_VertexID) {
continue;
}
read_boid(tmp_pos, tmp_vel, i);
float dist = distance(in_position, tmp_pos);
if (dist < 0.1) {
// alignment
boid_vel += tmp_vel;
// separation
boid_se += tmp_pos;
// cohesion
boid_co += tmp_pos;
count++;
}
}
if (count > 0) {
boid_vel /= count;
boid_co /= count;
boid_se /= count;
boid_vel += in_position - boid_co;
// boid_vel += in_position + boid_se;
float speed = length(boid_vel);
if (speed > MAX_SPEED) {
boid_vel *= MAX_SPEED / speed;
}
}
// handle framebuffer bounds
vec2 pos = in_position + (boid_vel * timedelta);
vec2 vel = in_velocity + boid_vel;
// float len = 1.0; // max(length(boid_vel), 0.1);
float dist_x_pos = 2.5 - pos.x;
float dist_x_neg = abs(-2.5 - pos.x);
float dist_y_pos = 1.0 - pos.y;
float dist_y_neg = abs(-1.0 - pos.y);
if (dist_x_pos < 0.1) {
vel += vec2(-1.0, 0.0);
}
if (dist_x_neg < 0.1) {
vel += vec2(1.0, 0.0);
}
if (dist_y_pos < 0.1) {
vel += vec2(0.0, -1.0);
}
if (dist_y_neg < 0.1) {
vel += vec2(0.0, 1.0);
}
out_position = pos;
out_velocity = vel;
}
#endif
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