In this episode of the Turntable Photogrammetry basic series, I will import the High Poly mesh into Blender and clean it up a bit before creating the Low Poly version.
Video Transcript
Hello everyone! In this episode of the Turntable Photogrammetry basic series, I will import the High Poly mesh into Blender and clean it up a bit before creating the Low Poly version.
I will need to remove unnecessary parts and close any holes, as they can cause issues with the Remesh tool, which I will use to create the Low Poly version.
To import the OBJ file, go to File Import OBJ and select the copy file, named High Poly, which was saved at the end of the previous episode.
To center the mesh in the viewport, I select it and press the period key on the numpad, or choose Frame Selected from the View menu in the 3D Viewport.
The object appears upside down and far from its Origin, which is placed at the center of the virtual world. However, I prefer to avoid moving or rotating it. I also don’t apply Loc Rot Scale transformations. This is necessary because Meshroom requires both versions to be in the same 3D space to correctly Bake the color Texture.
At this stage, what I need to do is switch to Smooth Shading, remove unnecessary geometry, close any holes, and make sure the Normals are correctly set. Before starting, though, I save the project as High Poly 1, just to be safe.
I set Smooth Shading for the object and then switch to Edit Mode. I select the entire main geometry by pressing L while hovering the mouse cursor over one of its vertices. Then, I invert the selection and delete the unwanted elements.
There are several ways to remove unnecessary elements. For example, I can select a part of an element to be removed and expand the selection using CTRL and numpad plus. This is the shortcut for the More operator in the Select menu.
Alternatively, I can use freehand selection by holding CTRL and right-click, which works best in Wireframe Mode, allowing me to select elements that are not in the foreground.
In general, I can use any selection tools and techniques that come to mind. For example, for more difficult areas, I can select a surrounding region and temporarily hide it with H, making it easier to select and delete the part I need. Hidden parts can be made visible again with ALT H.
All these holes need to be closed, preferably with a good amount of geometry, since they will later be adjusted with some sculpting. There are several techniques for this as well. For example, I can create concentric loops by selecting an edge ring and using extrusion, then closing the center with Merge At Center.
Another option is to use the Grid Fill tool, for which I recommend switching to Edge selection mode. This tool works if the perimeter’s vertex count is even, so in some cases, I may need to subdivide an edge to meet this condition.
In this case, Grid Fill didn’t work because I selected not only the perimeter of the hole but also a triangle. I simply need to deselect the extra edge and try again. However, the geometry was too irregular to get a good result, so I first extruded it, then beveled it, and finally closed it.
To check for any remaining holes, the easiest approach is probably to select everything and use the Select Boundary Loops operator. In this case, the operator didn’t return any elements, meaning the object is completely closed.
Now, I can switch to Sculpt Mode and refine the areas I manually closed to make them look more natural.
Holding SHIFT while left clicking in Sculpt Mode activates the Smooth tool, which is useful for eliminating small imperfections, usually caused by overlapping edges or faces.
To examine the Texture generated by Meshroom on this object, I drag the EXR file into a Shader Editor with the object’s default material. Then, I connect the Texture to the Base Color input of the material. In a 3D View, I switch to Rendered Mode to inspect the result.
Some errors are visible, mainly due to closing the holes, but they won’t be difficult to fix in Substance Painter or other software, including Blender itself. There is also a noticeable difference in brightness between the upper and lower halves, caused by the lighting conditions during the photo capture. However, there are ways to correct this as well.
Before wrapping up this episode, I save the project with a progressive number using Save Incremental. In the next episode, I will create a Low Poly version of the object. See you soon!