[Bf-blender-cvs] [fd9b3419eac] soc-2021-adaptive-cloth: adaptive_cloth: AdaptiveMesh: dynamic face sizing (for curvature)

[ishbosamiya]

Commit: fd9b3419eac7b2a63a8d835564dc3359b7735291
Author: ishbosamiya
Date:   Sun Sep 5 11:05:24 2021 +0530
Branches: soc-2021-adaptive-cloth
https://developer.blender.org/rBfd9b3419eac7b2a63a8d835564dc3359b7735291

adaptive_cloth: AdaptiveMesh: dynamic face sizing (for curvature)

Compute the dynamic face sizing with respect to curvature and do eigen
decomposition of the final sizing to add constraints with respect to
edge lengths and aspect ratio.

===================================================================

M	source/blender/blenkernel/intern/cloth_remesh.cc

===================================================================

diff --git a/source/blender/blenkernel/intern/cloth_remesh.cc b/source/blender/blenkernel/intern/cloth_remesh.cc
index 5801cc878fa..333c9bd58de 100644
--- a/source/blender/blenkernel/intern/cloth_remesh.cc
+++ b/source/blender/blenkernel/intern/cloth_remesh.cc
@@ -190,7 +190,7 @@ class Sizing {
   float2x2 m; /* in [1], the "sizing" tensor field given as `M` */
 
  public:
-  Sizing(float2x2 &&m) : m(m)
+  Sizing(const float2x2 &m) : m(m)
   {
   }
 
@@ -775,6 +775,45 @@ class AdaptiveMesh : public Mesh<NodeData<END>, VertData, EdgeData, FaceData> {
     return float3x2(f2 - f1, f3 - f1) * dm_inv;
   }
 
+  Sizing compute_dynamic_face_sizing(const AdaptiveFace &face) const
+  {
+    const float edge_length_min = 0.01;
+    const float edge_length_max = 1.0;
+    const float aspect_ratio_min = 0.2;
+    const float change_in_vertex_normal_max = 0.01;
+
+    BLI_assert(face.get_verts().size() == 3);
+    const auto &n1 = this->get_checked_node_of_vert(this->get_checked_vert(face.get_verts()[0]));
+    const auto &n2 = this->get_checked_node_of_vert(this->get_checked_vert(face.get_verts()[1]));
+    const auto &n3 = this->get_checked_node_of_vert(this->get_checked_vert(face.get_verts()[2]));
+
+    const float3x2 jacobian_normal = this->calculate_derivative(
+        face, n1.get_normal(), n2.get_normal(), n3.get_normal());
+    const float2x3 jacobian_normal_transpose = jacobian_normal.transpose();
+
+    const float2x2 m_crv = jacobian_normal_transpose * jacobian_normal;
+
+    const float2x2 m_hat = m_crv *
+                           (1.0 / (change_in_vertex_normal_max * change_in_vertex_normal_max));
+
+    /* Eigen Decomposition for adding the constraints */
+    const auto [q, lambda_hat] = m_hat.eigen_decomposition();
+    const auto lambda_tilda_1 = std::clamp(lambda_hat[0],
+                                           (1.0f / (edge_length_max * edge_length_max)),
+                                           (1.0f / (edge_length_min * edge_length_min)));
+    const auto lambda_tilda_2 = std::clamp(lambda_hat[1],
+                                           (1.0f / (edge_length_max * edge_length_max)),
+                                           (1.0f / (edge_length_min * edge_length_min)));
+    const auto lambda_tilda_max = std::max(lambda_tilda_1, lambda_tilda_2);
+    const auto lambda = float2(
+        std::max(lambda_tilda_1, aspect_ratio_min * aspect_ratio_min * lambda_tilda_max),
+        std::max(lambda_tilda_2, aspect_ratio_min * aspect_ratio_min * lambda_tilda_max));
+
+    const float2x2 m = q * float2x2(lambda[0], 0.0, 0.0, lambda[1]) * q.transpose();
+
+    return Sizing(m);
+  }
+
   /**
    * Computes and the `Sizing` of every `AdaptiveFace` of the mesh
    * based on the current state of the mesh and the scene.
@@ -783,9 +822,15 @@ class AdaptiveMesh : public Mesh<NodeData<END>, VertData, EdgeData, FaceData> {
    */
   blender::Map<FaceIndex, Sizing> compute_dynamic_face_sizing() const
   {
-    /* TODO */
+    blender::Map<FaceIndex, Sizing> face_sizing_map;
+
+    for (const auto &face : this->get_faces()) {
+      const auto sizing = this->compute_dynamic_face_sizing(face);
+
+      face_sizing_map.add_new(face.get_self_index(), sizing);
+    }
 
-    return blender::Map<FaceIndex, Sizing>();
+    return face_sizing_map;
   }
 
   /**