+
+static void ui_handler(goatkit::Widget *w, const goatkit::Event &ev, void *cls)
+{
+ if(w == bn_emitter) {
+ if(placing_emitter) {
+ placing_emitter = false;
+ slider_mass->hide();
+ } else {
+ if(mass_left > 0.0f) {
+ placing_emitter = true;
+ slider_mass->set_range(0, mass_left);
+ slider_mass->set_value(mass_left >= EM_MASS_DEFAULT ? EM_MASS_DEFAULT : mass_left);
+ slider_mass->show();
+ }
+ }
+ return;
+ }
+
+ if(w == slider_mass) {
+ printf("foo: %f\n", slider_mass->get_value());
+ }
+}
+
+static int pos_to_grid_x_noclamp(float x)
+{
+ return ((x / (float)FIELD_SIZE) + 0.5f) * (float)GRID_SIZE;
+}
+
+static int pos_to_grid_y_noclamp(float y)
+{
+ return ((y / (float)FIELD_SIZE) + 0.5f) * (float)GRID_SIZE;
+}
+
+static int pos_to_grid(float x, float y)
+{
+ int gx = pos_to_grid_x_noclamp(x);
+ int gy = pos_to_grid_y_noclamp(y);
+
+ if(gx < 0) gx = 0;
+ if(gx >= GRID_SIZE) gx = GRID_SIZE - 1;
+ if(gy < 0) gy = 0;
+ if(gy >= GRID_SIZE) gy = GRID_SIZE - 1;
+
+ return (gx << GRID_BITS) | gy;
+}
+
+static Vec2 grid_to_pos(int gx, int gy)
+{
+ float x = (((float)gx / (float)GRID_SIZE) - 0.5f) * (float)FIELD_SIZE;
+ float y = (((float)gy / (float)GRID_SIZE) - 0.5f) * (float)FIELD_SIZE;
+
+ return Vec2(x, y);
+}
+
+static void calc_contrib_bounds(const Vec2 &pos, float mass, Rect *rect)
+{
+ int gidx = pos_to_grid(pos.x, pos.y);
+ int gx = GRID_X(gidx);
+ int gy = GRID_Y(gidx);
+ int maxrange = (int)ceil(CONTRIB_RANGE(mass));
+
+ int sx = gx - maxrange;
+ int sy = gy - maxrange;
+ int ex = gx + maxrange;
+ int ey = gy + maxrange;
+
+ if(ex > GRID_SIZE) ex = GRID_SIZE;
+ if(ey > GRID_SIZE) ey = GRID_SIZE;
+
+ rect->x = sx < 0 ? 0 : sx;
+ rect->y = sy < 0 ? 0 : sy;
+ rect->width = ex - sx;
+ rect->height = ey - sy;
+}
+
+static void add_influence(const Vec2 &pos, float mass, float radius, const Rect &cbox)
+{
+ float *gptr = grid + cbox.y * GRID_SIZE + cbox.x;
+ Vec2 startpos = grid_to_pos(cbox.x, cbox.y);
+
+ for(int y=0; y<cbox.height; y++) {
+ for(int x=0; x<cbox.width; x++) {
+ Vec2 cellpos = Vec2(startpos.x + (float)x * GRID_DELTA, startpos.y);
+
+ Vec2 dir = cellpos - pos;
+ float dsq = dot(dir, dir);
+ float radsq = radius * radius;
+ if(dsq < radsq) {
+ dsq = radsq;
+ }
+
+ gptr[x] += mass / dsq;
+ }
+
+ startpos.y += GRID_DELTA;
+ gptr += GRID_SIZE;
+ }
+}
+
+static Vec2 calc_field_grad(int gidx)
+{
+ int gx = GRID_X(gidx);
+ int gy = GRID_Y(gidx);
+
+ int nidx = ((gx + 1 >= GRID_SIZE ? gx : gx + 1) << GRID_BITS) | gy;
+ int pidx = ((gx > 0 ? gx - 1 : gx) << GRID_BITS) | gy;
+ float dfdx = grid[nidx] - grid[pidx];
+
+ nidx = (gx << GRID_BITS) | (gy + 1 >= GRID_SIZE ? gy : gy + 1);
+ pidx = (gx << GRID_BITS) | (gy > 0 ? gy - 1 : gy);
+ float dfdy = grid[nidx] - grid[pidx];
+
+ return Vec2(dfdx, dfdy);
+}
+
+
+// ---- quad mesh operations ----
+
+static void destroy_quadmesh(QuadMesh *m)
+{
+ glDeleteBuffers(1, &m->vbo_v);
+ glDeleteBuffers(1, &m->vbo_uv);
+ glDeleteBuffers(1, &m->ibo);
+
+ delete [] m->v;
+ delete [] m->uv;
+ delete [] m->idx;
+}
+
+static void draw_quadmesh(const QuadMesh *m, unsigned int prim)
+{
+ glEnableClientState(GL_VERTEX_ARRAY);
+ glEnableClientState(GL_TEXTURE_COORD_ARRAY);
+
+ glBindBuffer(GL_ARRAY_BUFFER, m->vbo_v);
+ glVertexPointer(3, GL_FLOAT, 0, 0);
+
+ glBindBuffer(GL_ARRAY_BUFFER, m->vbo_uv);
+ glTexCoordPointer(2, GL_FLOAT, 0, 0);
+
+ glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+ glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m->ibo);
+ glDrawElements(prim, m->num_idx, GL_UNSIGNED_SHORT, 0);
+ glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+
+ glDisableClientState(GL_VERTEX_ARRAY);
+ glDisableClientState(GL_TEXTURE_COORD_ARRAY);
+}
+
+static void gen_quad_plane(QuadMesh *m, float width, float height, int usub, int vsub)
+{
+ Vec3 *vptr;
+ Vec2 *uvptr;
+ uint16_t *iptr;
+
+ if(usub < 1) usub = 1;
+ if(vsub < 1) vsub = 1;
+
+ int uverts = usub + 1;
+ int vverts = vsub + 1;
+ m->num_verts = uverts * vverts;
+ m->num_quads = usub * vsub;
+ m->num_idx = m->num_quads * 4;
+
+ vptr = m->v = new Vec3[m->num_verts];
+ uvptr = m->uv = new Vec2[m->num_verts];
+ iptr = m->idx = new uint16_t[m->num_idx];
+
+ float du = 1.0f / (float)usub;
+ float dv = 1.0f / (float)vsub;
+
+ float u = 0.0f;
+ for(int i=0; i<uverts; i++) {
+ float x = (u - 0.5f) * width;
+ float v = 0.0f;
+ for(int j=0; j<vverts; j++) {
+ float y = (v - 0.5f) * height;
+
+ *vptr++ = Vec3(x, 0, y);
+ *uvptr++ = Vec2(u, v);
+
+ if(i < usub && j < vsub) {
+ int idx = i * vverts + j;
+
+ *iptr++ = idx;
+ *iptr++ = idx + 1;
+ *iptr++ = idx + vverts + 1;
+ *iptr++ = idx + vverts;
+ }
+
+ v += dv;
+ }
+ u += du;
+ }
+
+ glGenBuffers(1, &m->vbo_v);
+ glBindBuffer(GL_ARRAY_BUFFER, m->vbo_v);
+ glBufferData(GL_ARRAY_BUFFER, m->num_verts * 3 * sizeof(float), m->v, GL_STATIC_DRAW);
+
+ glGenBuffers(1, &m->vbo_uv);
+ glBindBuffer(GL_ARRAY_BUFFER, m->vbo_uv);
+ glBufferData(GL_ARRAY_BUFFER, m->num_verts * 2 * sizeof(float), m->uv, GL_STATIC_DRAW);
+
+ glGenBuffers(1, &m->ibo);
+ glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m->ibo);
+ glBufferData(GL_ELEMENT_ARRAY_BUFFER, m->num_idx * sizeof(uint16_t), m->idx, GL_STATIC_DRAW);
+
+ glBindBuffer(GL_ARRAY_BUFFER, 0);
+ glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+}
+
+static void spawn_particle(const Vec2 &pos, const Vec2 &vel, float mass)
+{
+ int gidx = pos_to_grid(pos.x, pos.y);
+
+ if(grid_part[gidx]) {
+ // merge with existing
+ Particle *p = grid_part[gidx];
+ p->vel += vel;
+ p->mass += mass;
+ p->radius = MASS_TO_RADIUS(p->mass);
+
+ } else {
+ Particle *p = alloc_particle();
+ p->pos = pos;
+ p->vel = vel;
+ p->mass = mass;
+ p->radius = MASS_TO_RADIUS(mass);
+ grid_part[gidx] = p;
+
+ add_particle(p);
+ }
+}
+
+static void add_particle(Particle *p)
+{
+ if(plist) plist->prev = p;
+
+ p->next = plist;
+ p->prev = 0;
+ plist = p;
+}
+
+static void remove_particle(Particle *p)
+{
+ assert(plist->prev == 0);
+
+ if(plist == p) {
+ assert(p->prev == 0);
+ plist = p->next;
+ }
+ if(p->prev) {
+ p->prev->next = p->next;
+ }
+ if(p->next) {
+ p->next->prev = p->prev;
+ }
+ p->prev = p->next = 0;
+}
+
+// particle allocator
+#define MAX_PFREE_SIZE 256
+static Particle *pfree_list;
+static int pfree_size;
+
+static Particle *alloc_particle()
+{
+ if(pfree_list) {
+ Particle *p = pfree_list;
+ pfree_list = pfree_list->next;
+ pfree_size--;
+ return p;
+ }
+
+ return new Particle;
+}
+
+void free_particle(Particle *p)
+{
+ if(pfree_size < MAX_PFREE_SIZE) {
+ p->next = pfree_list;
+ p->prev = 0;
+ pfree_list = p;
+ pfree_size++;
+ } else {
+ delete p;
+ }
+}