Printing amazing full-color, real to the touch textures using the Stratasys J735 or J750 printer and Agilus30 White simulated rubberlike material is truly amazing. Previously, we discussed some ways to create colored 3D texture files for printing through the use of wood and stone 2D image files. In this article, I’m going to show you some tips and tricks when creating your full-color 3D models in Adobe Photoshop to create a leather texture. Additionally, I’ll share some things to look out for when you are creating your models to avoid not-so-appealing final models, and what you can do to fix these issues.
Creating and Scaling Your Image
Let’s refresh some concepts before creating our leather texture. To create a 3D textured model in Photoshop, you’ll need to either have a bump map that matches a full-color 2D image or create a bump map image using a normal 2D full-color file. Ideally, you would have access to a matching set of images, but if you don’t you would only need to desaturate your full-color image to adjust the levels, contrast and brightness. This will contain all the data that you need to go from 2D to 3D to print. From there, you can use the 3D Textures feature in SOLIDWORKS to apply this bump map to a surface and extrude the textures from the surface. If you prefer using Photoshop you can use a similar function to convert the image from 2D to 3D.
With our leather texture, we’re first going to look at how scaling an image can affect the file’s outcome and how sometimes we need to scale our images in the design phase to prevent issues from occurring when printing. In these images, you’ll see four different scales of the same leather texture, each with the same x/y boundary or 4 in. x 4 in. On the left is the 100% image scale, followed by 200%, 300% and 400%. As you can see, the grain of the leather texture gets larger and more pronounced with each scale and the resolution decreases as we’re expanding the size of each pixel to accommodate this change in the image dimension.
The next set of images show our parts' look after they were printed on the Stratasys J750. As shown on these images, the highest resolution variant doesn’t always end up being the best quality variant. The 200% and 300% scale images, to my eyes, best represent the end “leather” look that we’re going for, compared to traditional leather look and feel. After inspecting the final prints, I also noticed the 100% scale has grain is so small that it resembles tiny hairs and the 400% scale model has comically oversized grain that just doesn't look real. If your model is going to use a complicated texture like leather, it's important to experiment with image scale before running a large print job of parts, since you may not see issues until after their printed. Depending on the size of the part you are making it will save time and material in having to reprint the entire assembly a second time.
Changing the Scale of Your Image
Now, how do we make this kind of change? It’s easy! To adjust the scale of both the image and the texture, double-click on the diffuse layer, hold Control (CTRL) and T to open the transform menu and then change the scale on the top menu bar to whatever you feel would work best. Don’t forget to make the same adjustment to the bump layer, because otherwise they won’t line up and your color won’t fill the grain perfectly as you intend it to when doing this type of work.
Controlling Model Thickness
While the scale is an important factor in adjusting models in order to get a good final result, understanding how your model’s thickness works is another key in getting a good-looking textures that feel right.
Knowing the correct model thickness for this process is all about understanding how the Stratasys J735 and J750 print process works when using full color VRML or OBJ files. Adjusting the model thickness will need to be done when designing your model in either 3D CAD or Photoshop. When creating an extrusion that will be utilizing color, regardless of whether it is Agilus or Vero (flexible or rigid), the colors will only print 1 mm deep into the surface of the model and you want a minimum of 2 mm of additional total thickness to ensure a solid white core. This will help optimize the colors on the exterior of the model. So, you’re going to want to extrude the model to at least 3 mm, which is a good rule of thumb to remember for most texture work in general. If you are going to scale the model in the printer’s software, you should keep this in mind along with extruding the 2D model in Photoshop to compensate for this correctly. Other things to note here with Agilus30 White are that the lighter the color is on the outside, the more flexible the model will be as any lighter colors will have more Agilus30 content, and as a result will have a lower ShoreA durometer value. The total core thickness can improve flexibility to a point, but past 1 cm of thickness, the interior of the white core will be rigid black, which will make thicker models actually less flexible than you would expect.
Bump Map Surface Detail Settings
Understanding the depth surface detail settings used for the final bump map generation is one of the most important important parameters that can be changed to affect the look of your final printed model. To really understand how this works, it helps to look at an example of good surface detail settings versus bad surface details settings.
In the next set of images, the one to the left shows our 200% scale model with the correct surface detail settings for the smooth leather with a slightly bumpy finish that you’re looking for. The image to the right shows the same 200% scale model with a much deeper range of surface detail settings. The model on the left is a perfect blend of physical detail and subtle smoothness, while the model on the right has very deep valleys and high peaks which look bad and don’t feel smooth at all. A good way to describe it is that the shallower depth setting on the left actually does feel smooth like leather, while the part on the right feels rough like sandpaper. The printer will need to create supports around certain areas (circled in red) which cause discoloration in that region of the print which causes the part to look even less like leather. Furthermore, very thin peaks on the x/y plane are also discolored and as we have learned, the features need to be at least 1 mm in thickness to obtain proper coloring, which is of most concern in the z dimension but is also applicable to the x/y too! Basically, thin features won’t have great coloring is the rule of thumb, regardless of the dimension it is thin on.
It may seem like this is going to take quite a bit of work to get just right, but that’s incorrect. The setting in Photoshop which adjusts the overall depth at which your bump mapping extrudes from and cuts into the surface of the model, (aka the parameters which control the surface detail) can be found under the 3D menu in the 3D print settings prompter menu. As you can see in the next Photoshop screenshot, all we need to control is the minimum and maximum values for the surface detail. This field is in inches, so keep in mind that a deviation of -.25 for the minimum will cut in a quarter of an inch into your model, while a maximum of .25 will extrude a quarter of an inch out of your model. For this project, I found that the best settings were + and – 0.01”, but depending on the texture that you’re working with, this may not be the same. As an example, our stone model from our previous blog had a minimum of -.015, and a maximum of .025, which resulted in a far more dramatic rocky texture in our model.
Over the past few articles, we’ve explained how to take a CAD model in SOLIDWORKS and apply texture and color to it, build a full-color 3D texture model from scratch in Adobe Photoshop CC and discovered some easy tricks that can help perfect your model before you ever print it. Image scaling can lead to major quality improvements depending on the size of the final part and the starting resolution of the image, as sometimes your image features are going to be just too small to print using the original image scaling. Making sure that your model is the right thickness is both important for minimizing part cost and print time, while also ensuring that you are getting the right level of flexibility and color out of the Agilus30 White material. Finally, surface detail settings play a major roll in how the final texture comes out, and adjustment of these settings are a breeze!
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