mesh: impl uv remapping

docs/source/blender.md

@@ -20,5 +20,6 @@ python -m kiui.cli.blender_render --mesh chest.glb --gpu 0 --depth --normal --al
 Features include:
 * Set which GPU to use with `--gpu 0` for `CYCLES` rendering engine.
 * Render with random built-in HDRI environment texture shading (check `assets/blender_lights`).
-* Optionally render depth (`exr`), normal, and albedo.
-* Empirical cleaning of the scene (remove the annoying plane under the object).
+* Empirical cleaning of the scene (remove the annoying plane under the object).
+* Optionally render depth (`exr`), normal.
+* Optionally render PBR (albedo, metallic, roughness).

kiui/mesh.py

@@ -546,6 +546,35 @@ def auto_uv(self, cache_path=None, vmap=True):
             vmapping = torch.from_numpy(vmapping.astype(np.int64)).long().to(self.device)
             self.align_v_to_vt(vmapping)
 
+    def remap_uv(self, v):
+        """ remap uv texture (vt) to other surface.
+
+        Args:
+            v (torch.Tensor): the target mesh vertices, float [N, 3].
+        """
+
+        assert self.vt is not None
+
+        if self.v.shape[0] != self.vt.shape[0]:
+            self.align_v_to_vt()
+
+        # find the closest face for each vertex
+        import cubvh 
+        BVH = cubvh.cuBVH(self.v, self.f)
+        dist, face_id, uvw = BVH.unsigned_distance(v, return_uvw=True)
+
+        # get original uv
+        faces = self.f[face_id].long()
+        vt0 = self.vt[faces[:, 0]]
+        vt1 = self.vt[faces[:, 1]]
+        vt2 = self.vt[faces[:, 2]]
+
+        # calc new uv
+        vt = vt0 * uvw[:, 0:1] + vt1 * uvw[:, 1:2] + vt2 * uvw[:, 2:3]
+
+        return vt
+
+
     def align_v_to_vt(self, vmapping=None):
         """ remap v/f and vn/fn to vt/ft.
 

tests/test_remap_uv.py

@@ -0,0 +1,31 @@
+import kiui
+from kiui.mesh import Mesh
+from kiui.mesh_utils import clean_mesh
+
+import torch
+import argparse
+
+parser = argparse.ArgumentParser()
+parser.add_argument("--mesh", type=str)
+parser.add_argument("--mesh2", type=str)
+parser.add_argument("--out", type=str, default='out.glb')
+opt = parser.parse_args()
+
+# load input mesh
+mesh = Mesh.load(opt.mesh)
+
+# must have texture to remap uv
+assert mesh.albedo is not None
+
+# load target mesh
+mesh2 = Mesh.load(opt.mesh2)
+
+# no texture for this mesh
+assert mesh2.albedo is None
+
+# remap uv
+mesh2.albedo = mesh.albedo
+mesh2.vt = mesh.remap_uv(mesh2.v)
+
+# write
+mesh2.write(opt.out)