In this episode of the basic turntable photogrammetry series, we will look at some useful tools for correcting errors in the Textures imported into the Substance project.
Video Transcript
Hello everyone! In this episode of the basic turntable photogrammetry series, we will look at some useful tools for correcting errors in the Textures imported into the Substance project.
I will also discuss the use of some layers that, with different intensities and application modes, can help adjust the lighting or tone of various parts of the Base Color Texture.
This phase of the workflow is the one that allows for the most customization or, so to speak, personal interpretation of the work to be done. So, don’t focus on the final result I achieve, but rather on the tools and techniques that may be useful to you.
I'm starting by trying to correct the brightness differences between the upper and lower parts of the model. As mentioned in the first episode of this series, these differences are due to lighting errors in the real scene when the photos were taken. To view the Base Color without shading effects, I'm switching to Base Color view in a 2D workspace. You can also try correcting these errors directly in the Base Color Texture using other programs before importing it into Substance.
One method to lighten or darken specific areas is to add a Fill Layer for the Base Color channel only, assigning it a uniform color and using a blending mode such as Hard Light, Overlay, Value, or others.
You will then need to apply a black layer mask to this Fill Layer and start painting on the mask to define the areas where the Fill Layer should be applied. After the first brushstrokes, you can adjust the color or the intensity of the Fill Layer application until you achieve the desired result.
In these cases, it is advisable to use a brush with very soft edges to avoid creating sharp differences between areas. Ideally, a graphics tablet should be used to control the intensity of the strokes, but alternatively, you can adjust the brush opacity in its settings panel.
Remember to occasionally switch to Material view mode, because the Base Color view mode only displays the pure color map, which does not take into account ambient lighting, Roughness, or the Normal Map.
When switching to Material view mode in the 3D View, I noticed that I had not disabled all channels except Color in the Fill Layer set to Hard Light. The new Fill Color was also affecting the Roughness and Glossiness channels. I quickly fix this mistake by leaving only the Color channel enabled.
You can also add additional layers for the Base Color only and adjust their color to use different blending modes. For example, you can use Saturation or Tint modes to adjust the saturation and hue of the Base Color, or Multiply mode with a dark color to darken the Base Color. Of course, everything depends on your project and the final result you want to achieve.
Two other tools that can be used in this phase are Smudge and Clone, which allow you to blend or clone parts of the Materials, respectively. I said they can modify the Materials, not just the colors, because these brushes actually affect all the channels they are enabled for, not just the Color channel. This means they also allow us to modify the Roughness and Normals of the affected areas.
In both cases, to use them, you need to create a new empty Layer, changing its blending mode to Passthrough. Be careful to create a paint Layer, not a Fill Layer! In the Layer panel, you can choose which channels to affect and which to exclude.
However, be extra careful at this stage because the selection of channels to influence does not take place inside the Properties panel of the paint Layer, as one might expect. Instead, it is done in the dropdown menu located at the top left of the Layers panel. This menu is set to Base Color by default, and the Layer mode will be Passthrough only for the Base Color channel!
Therefore, you must select the other channels you want to influence and change the Layer mode to Passthrough each time. In our case, we are particularly interested in the Base Color, Normal, Roughness, Glossiness, and Ambient Occlusion channels, but in other situations, you might also want to perform this operation for additional channels such as Metallic, Height, or Specular.
The Passthrough mode ensures that this Layer affects all the underlying Layers. So, I select the Smudge tool from the program’s toolbar and start applying a few strokes here and there on the paint Layer to show you the effects.
A walnut shell is not the best choice for using Smudge, because I want to preserve the details on this object, not blur them! However, I wanted to show you how to use this tool, as it might come in handy in other situations. Now, I will delete this paint Layer to demonstrate how to use Clone.
To use the Clone brush, you also need to create a new paint Layer in Passthrough mode, and once again, you must set this mode for the channels you want to affect, just as we did earlier with the Smudge tool.
The Clone tool must also be selected from the Substance toolbar, but in this case, we have two available modes. I will show their differences shortly.
To use the Clone tool, the first step is to define the starting point of the portion to be cloned. This is done by clicking the left mouse button while holding down the V key.
Once done, you can release the V key and the left mouse button. Move the mouse cursor to the area you want to fix, then click and drag to clone the source to the new destination. This way, I can easily correct the material in areas where, for example, the support toothpicks were incorrectly mapped onto the Texture of the High Poly object. More generally, you can remove or add details or features on the object.
The difference between Relative and Absolute mode is simply that, in Relative mode, the source point of the cloning follows the mouse cursor after performing the operation. In Absolute mode, on the other hand, the source point remains in its original position relative to the 3D view, even if we move the mouse cursor or change the viewpoint in the scene.
Anyway, I will stop making changes here. The goal was not to achieve a perfect object but rather to go through useful tools and techniques for correcting lighting issues or other errors in the original Base Color, and beyond.
To wrap up this episode, I check that all channels have a Texture or at least a base color, then I export the Textures to disk to apply them to the model in Blender, as we will see in the next episode. See you soon!