In this episode of the basic series on turntable photogrammetry, I will show you how to transfer the Color information from the original High Poly reconstruction to the Low Poly object obtained in Blender.
Video Transcript
Hello everyone! In this episode of the basic series on turntable photogrammetry, I will show you how to transfer the Color information from the original High Poly reconstruction to the Low Poly object obtained in Blender.
This process is called Baking, and in this episode, we will use it to remap the Base Color Texture from the High Poly geometry so that we can apply this Texture to the Low Poly object, which has its own UV unwrapping, different from that of the High Poly geometry.
In Meshroom, to perform Baking on an external object, I first need to create a new Texturing node to insert into the processing pipeline. This can be done by duplicating the original node, selecting it, and pressing SHIFT D.
In the new node, I will need to remove the connection to the Mesh input because I will be using the Low Poly object, exported at the end of the previous tutorial, as an external geometry onto which the Textures generated here in Meshroom for the original High Poly version will be mapped. The removal can be done by right clicking on the connection and then selecting Remove from the menu that appears on the screen.
Now I need to configure some parameters in the settings of the new Texturing node, starting with the Mesh field, where I have to copy the path of the Low Poly file I exported from Blender.
I set the desired texture resolution freely. I recommend keeping the default value, 8192, to maintain good quality, as this Texture will still be processed further later.
It is possible to choose a different format for both the geometry and the Textures to be generated. For example, I am selecting FBX as the mesh format and PNG for the images. Finally, I am disabling UDIM mode for Texture creation.
To bake the details from the High Poly mesh, I need to specify the path of the High Poly object in the Ref Mesh field of the node.
After entering this path, options will appear for generating the Normal Map and Displacement Map, which will store the details of the High Poly geometry. I am setting PNG as the format for the Normal Map, in the Bump Mapping section. The only available format for the Displacement Map is EXR, because the data for this type of map is stored with a higher bit depth.
Now, I just need to save the project and click Start. Since I haven’t modified any other nodes from the last execution, only the new Texturing node will be processed, so this computation won’t take much time.
Once the process is complete, the generated Texture images will be located in a new subfolder inside the Texturing folder within the project's Cache directory on disk. As you can see, the Normal Map obtained this way appears faceted, even though the Low Poly geometry exported from Blender had Smooth Shading enabled.
I haven’t found any valid solutions to fix this issue in Meshroom, not even by trying other processing nodes or exporting with Smoothing Groups from Blender. No luck. However, I didn’t lose sleep over this problem because baking the Normal Map from the High Poly version to the Low Poly one can easily be done in Blender or Substance Painter.
What really matters to me at the end of this process is the new Base Color Texture, which has been reconstructed based on the UV unwrapping I created for the Low Poly object. This Texture will be easier to edit compared to the one initially generated by Meshroom, which you may have briefly seen in a previous episode.
Additionally, Meshroom sometimes doesn’t generate a single EXR map for the Base Color, but rather multiple Textures, associating them with multiple sub materials. This can make it difficult to bake them into a single color Texture in external programs. In such cases, baking the Base Color onto the Low Poly version, which has only one Material here in Meshroom, can save a lot of trouble.
To wrap up, from this phase, we will keep only the new Base Color Texture in PNG format. In the next episode, I will show you how to bake Normal Maps in Substance Painter and how to set up the basic PBR material. See you next time!