VRML Files for PolyJet
In our previous tutorial, we defined STLs and explained best practices for using them. In this tutorial, we will explain VRML files and their expanded capabilities beyond basic geometric representation.
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Step 1: Introduction
In our previous tutorial, we defined STLs and explained best practices for using them. In this tutorial, we will explain VRML files and their expanded capabilities beyond basic geometric representation.
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Step 2: VRML Files
Overview
Virtual Reality Modeling Language (VRML) is a standard file format (with the extension .wrl) for representing 3D interactive graphics. It provides the capability to apply colors and texture to a model, enabling it to be 3D printed with those textures.
Many design softwares enable you to design VRML or export VRML files that contain color and texture information.
VRML file wiith realistic woodgrain and display screen simulation
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Step 3: Color Assignments
There are four ways to assign color with VRML. Different software packages enable the export of some or all of these methods.
1. Color per object, mesh, or shell:
The first is color per object, mesh, or shell, in which you assign each component of an assembly with a solid color (usually referred to as diffuse color or material color).
2. Color per face:
Next is color per face, in which you assign a distinct color to each triangle or face of the model. A face can be anything from one triangle in a mesh to as many polygons as you select.
3. Color per vertex:
The third way you can designate a color is by assigning a different color to every vertex of every triangle in the design file. Each color value gets interpolated across the mesh. Note that the quality of the color across the whole part is entirely dependent on the mesh density.
4. Color by texture / UV mapping:
Finally, you may also assign color by texture, or UV mapping. This type of file shows the most detailed color information.
This is the process of adding an image or graphics to a 3D geometry. Color information is stored in a 2D image file, which is related to the coordinates of the mesh. Texture-mapped models are then essentially “wrapped” with the texture in a process called UV mapping.
For example, using UV-mapping, you can apply any image— including logos, text, and barcodes— as a texture to make your part look truly realistic.
Exact product simulation achived through textures
Special textures can even be used by certain design packages to alter the surface geometry of the part through a process called bump mapping, and then converted into a displaced geometry. Read this tutorial to find out more.
The main steps for applying texture are:
a. Design a 3D object, such as the cube shown above.
b. Map and unwrap the 3D object’s geometry, so that it is represented in a 2D plane.
c. Import the 2D image texture.
d. Align the geometry map and texture image.
e. Overlay the texture image onto the part’s geometry map. This process is called UV mapping. (UV are coordinates found on the 2D image plane that are mapped to the 3D XYZ coordinates)
f. Use these mapped UV coordinates to “wrap” the 2D image onto the original 3D geometry.
Textures can also include transparency.
Texture with transparent gradient
NOTE: In GrabCAD Print, you can override these textures with a different color/material assignment.
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Step 4: Anatomy of a VRML file
With texture-mapped models, you will need two files:
· a VRML (.wrl) file
· an image file with the texture or images included
The image file resolution should be at least 600 DPI. Lower resolutions may reduce print quality.
Components of one VRML file: 2 image textures (e.g., PNG), and 1 mesh file (.wrl)
OBJ is another advanced file type with color and transparency capabilities. OBJs also have some additional capabilities, which we will discuss in the next tutorial of this series.
We hope this tutorial encourages you to use VRML files in your PolyJet 3D prints. Reach out if you have any questions or comments, and be sure to read about mesh file considerations for PolyJet AM in tutorial 1 of this series.
