added forces + damping, k factors

[hair] / src / hair.cc

diff --git a/src/hair.cc b/src/hair.cc
index 33bdd0d..0fc026d 100644 (file)
--- a/src/hair.cc
+++ b/src/hair.cc
@@ -8,13 +8,24 @@
 #include "kdtree.h"
 #include "hair.h"
 
+/* spring constant */
+
+#define K_ANC 4.0
+#define DAMPING 1.5
+
 struct Triangle {
        Vec3 v[3];
        Vec3 n[3];
 };
 
-Hair::Hair() {}
-Hair::~Hair() {}
+Hair::Hair()
+{
+       hair_length = 0.5;
+}
+
+Hair::~Hair()
+{
+}
 
 static Vec3 calc_rand_point(const Triangle &tr, Vec3 *bary)
 {
@@ -34,7 +45,6 @@ static Vec3 calc_rand_point(const Triangle &tr, Vec3 *bary)
        bary->y = v;
        bary->z = c;
 
-//     printf("u %f v %f c %f sum: %f\n", u, v, c, u+v+c);
        return rp;
 }
 
@@ -72,7 +82,7 @@ static void get_spawn_triangles(const Mesh *m, float thresh, std::vector<Triangl
                        faces->push_back(t);
                }
        }
-       printf("spawn tri AABB: min y: %f max y: %f\n", min_y, max_y);
+/*     printf("spawn tri AABB: min y: %f max y: %f\n", min_y, max_y);*/
 }
 
 bool Hair::init(const Mesh *m, int max_num_spawns, float thresh)
@@ -104,28 +114,99 @@ bool Hair::init(const Mesh *m, int max_num_spawns, float thresh)
                                continue;
                }
 
+               HairStrand strand;
                /* weighted sum of the triangle's vertex normals */
-               Vec3 spawn_dir = rtriangle.n[0] * bary.x + rtriangle.n[1] * bary.y + rtriangle.n[2] * bary.z;
-               spawn_directions.push_back(normalize(spawn_dir));
-               spawn_points.push_back(rpoint);
+               strand.spawn_dir = normalize(rtriangle.n[0] * bary.x + rtriangle.n[1] * bary.y + rtriangle.n[2] * bary.z);
+               strand.spawn_pt = rpoint;
+               hair.push_back(strand);
+
                kd_insert3f(kd, rpoint.x, rpoint.y, rpoint.z, 0);
        }
 
        kd_free(kd);
+
+       for(size_t i=0; i<hair.size(); i++) {
+               hair[i].pos = hair[i].spawn_pt + hair[i].spawn_dir * hair_length;
+
+               /* orthonormal basis */
+               Vec3 vk = hair[i].spawn_dir;
+               Vec3 vi = Vec3(1, 0, 0);
+               if(fabs(vk.x > 0.99)) {
+                       vi = Vec3(0, -1, 0);
+               }
+               Vec3 vj = normalize(cross(vk, vi));
+               vi = cross(vj, vk);
+
+               /* identity when the hair points to the z axis */
+               Mat4 basis = Mat4(vi, vj, vk);
+
+               for(int j=0; j<3; j++) {
+                       float angle = (float)j / 3.0 * 2 * M_PI;
+                       /* dir of each anchor relative to hair root */
+                       Vec3 dir = Vec3(cos(angle), sin(angle), 0);
+                       dir = basis * dir;
+                       hair[i].anchor_dirs[j] = hair[i].pos + dir - hair[i].spawn_pt;
+               }
+       }
        return true;
 }
 
+static Vec3 dbg_force;
 void Hair::draw() const
 {
        glPushAttrib(GL_ENABLE_BIT);
-       glDisable(GL_DEPTH_TEST);
+//     glDisable(GL_DEPTH_TEST);
        glDisable(GL_LIGHTING);
-       glPointSize(2);
-       glBegin(GL_POINTS);
-       for(size_t i = 0; i < spawn_points.size(); i++) {
+       glPointSize(5);
+       glLineWidth(3);
+
+       glBegin(GL_LINES);
+       for(size_t i=0; i<hair.size(); i++) {
+               glColor3f(1, 0, 1);
+               Vec3 p = xform * hair[i].spawn_pt;
+               glVertex3f(p.x, p.y, p.z);
+               Vec3 dir = normalize(hair[i].pos - p) * hair_length;
+               Vec3 end = p + dir;
+               glVertex3f(end.x, end.y, end.z);
+/*
                glColor3f(1, 1, 0);
-               glVertex3f(spawn_points[i].x, spawn_points[i].y, spawn_points[i].z);
+               glVertex3f(hair[i].pos.x, hair[i].pos.y, hair[i].pos.z);
+               Vec3 end = hair[i].pos + dbg_force * 2.0;
+               glVertex3f(end.x, end.y, end.z);
+               */
        }
        glEnd();
+
+       /*
+       glBegin(GL_POINTS);
+       glColor3f(0.5, 1.0, 0.5);
+       for(size_t i = 0; i < hair.size(); i++) {
+               Vec3 p = xform * (hair[i].spawn_pt + hair[i].spawn_dir * hair_length);
+               glVertex3f(p.x, p.y, p.z);
+       }
+       glEnd();*/
+
        glPopAttrib();
 }
+
+void Hair::set_transform(Mat4 &xform)
+{
+       this->xform = xform;
+}
+
+void Hair::update(float dt)
+{
+       for(size_t i = 0; i < hair.size(); i++) {
+               /* in local space */
+               Vec3 hair_end = hair[i].spawn_pt + hair[i].spawn_dir * hair_length;
+               Vec3 anchor = xform * hair_end;
+
+               Vec3 force = (anchor - hair[i].pos) * K_ANC;
+
+               Vec3 accel = force; /* mass 1 */
+               hair[i].velocity += ((-hair[i].velocity * DAMPING) + accel) * dt;
+               hair[i].pos += hair[i].velocity * dt;
+
+               dbg_force = force;
+       }
+}