Fix T30941: Add cloth air pressure simulation

This adds some basic simulation of internal air pressure inside of
closed cloth mesh objects.

Reviewed By: Jacques Lucke

Differential Revision: http://developer.blender.org/D5473

1 files changed, 24 insertions, 0 deletions

diff --git a/source/blender/physics/intern/implicit_blender.c b/source/blender/physics/intern/implicit_blender.c
index d8b3f647591..fa093f482f7 100644
--- a/source/blender/physics/intern/implicit_blender.c
+++ b/source/blender/physics/intern/implicit_blender.c
@@ -1469,6 +1469,7 @@ void BPH_mass_spring_force_face_wind(
 
   /* calculate face normal and area */
   area = calc_nor_area_tri(nor, data->X[v1], data->X[v2], data->X[v3]);
+  /* The force is calculated and split up evenly for each of the three face verts */
   factor = effector_scale * area / 3.0f;
 
   world_to_root_v3(data, v1, win, winvec[v1]);
@@ -1481,6 +1482,29 @@ void BPH_mass_spring_force_face_wind(
   madd_v3_v3fl(data->F[v3], nor, factor * dot_v3v3(win, nor));
 }
 
+float BPH_tri_tetra_volume_signed_6x(Implicit_Data *data, int v1, int v2, int v3)
+{
+  /* The result will be 6x the volume */
+  return volume_tri_tetrahedron_signed_v3_6x(data->X[v1], data->X[v2], data->X[v3]);
+}
+
+void BPH_mass_spring_force_pressure(
+    Implicit_Data *data, int v1, int v2, int v3, float pressure_difference)
+{
+  float nor[3], area;
+  float factor;
+
+  /* calculate face normal and area */
+  area = calc_nor_area_tri(nor, data->X[v1], data->X[v2], data->X[v3]);
+  /* The force is calculated and split up evenly for each of the three face verts */
+  factor = pressure_difference * area / 3.0f;
+
+  /* add pressure to each of the face verts */
+  madd_v3_v3fl(data->F[v1], nor, factor);
+  madd_v3_v3fl(data->F[v2], nor, factor);
+  madd_v3_v3fl(data->F[v3], nor, factor);
+}
+
 static void edge_wind_vertex(const float dir[3],
                              float length,
                              float radius,