Add skybox textures and cube model

grk/project/models/cube.obj

@@ -0,0 +1,40 @@
+# Blender v2.90.0 OBJ File: ''
+# www.blender.org
+mtllib cube.mtl
+o Cube
+v -10.000000 -10.000000 10.000000
+v -10.000000 10.000000 10.000000
+v -10.000000 -10.000000 -10.000000
+v -10.000000 10.000000 -10.000000
+v 10.000000 -10.000000 10.000000
+v 10.000000 10.000000 10.000000
+v 10.000000 -10.000000 -10.000000
+v 10.000000 10.000000 -10.000000
+vt 0.375000 0.000000
+vt 0.625000 0.000000
+vt 0.625000 0.250000
+vt 0.375000 0.250000
+vt 0.625000 0.500000
+vt 0.375000 0.500000
+vt 0.625000 0.750000
+vt 0.375000 0.750000
+vt 0.625000 1.000000
+vt 0.375000 1.000000
+vt 0.125000 0.500000
+vt 0.125000 0.750000
+vt 0.875000 0.500000
+vt 0.875000 0.750000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 0.0000 1.0000
+vn 0.0000 -1.0000 0.0000
+vn 0.0000 1.0000 0.0000
+usemtl _PBR
+s 1
+f 1/1/1 2/2/1 4/3/1 3/4/1
+f 3/4/2 4/3/2 8/5/2 7/6/2
+f 7/6/3 8/5/3 6/7/3 5/8/3
+f 5/8/4 6/7/4 2/9/4 1/10/4
+f 3/11/5 7/6/5 5/8/5 1/12/5
+f 8/5/6 4/13/6 2/14/6 6/7/6