Introduction: Understanding virtual materials in simulation
In this article we want to briefly introduce fundamental principles of what virtual materials are made of. Materials management involves several complex methods, and the glossary can sometimes lead to confusion. After presenting some of the principles and methods, we will introduce some simple examples of materials management using the Ocean™ software and its virtual measurement tools.
To see objects in a 3D world, every surface of each object has to interact with light. Sensor models (cameras) are required for capturing all these interactions and outputting them as a commonly used rendered image.
The importance of accurate material representation in 3D simulation
For several reasons (memory consumption, artistic approach, simple use), some methods are physically wrong as they are only based on the final appearance of the object. On the other hand, some methods define models with measured data, allowing physically-true predictive behavior of the surface. To achieve accurate digital materials visualization, Ocean™ base its methodology on precise material spectral measurements, exact solution of geometry optics and advanced ray tracing technologies.
Ocean™'s science-based approach to material simulations
Ocean™ uses a tree structure to represent material properties, allowing for both simple and detailed models when rendering. Models can go as far as requiring measured data produced by dedicated devices. This rigorous approach enables:
- Accurate optical characterization of industrial materials such as glass, coatings, and plastics.
- Physically true rendering techniques to ensure precise light interactions.
- A balance between real-world visualization and engineering accuracy.
Following presentations aim at exploring how the complex world of materials is managed by modern softwares with common categories and to see how Ocean™ handles them.
Figure 1 - Various light/surface interactions (see further in "Materials Properties") captured by a camera.
Key components of virtual material simulation
“Material” is a global name which defines more complex concepts with a combination of several data values : shader or texture or both at the same time.
Consideration of all of the following components is necessary to ensure that material appearance predictions are physically accurate and reliable for use in R&D development or advanced prototyping.
Figure 2 - Example of a material in Ocean™ : Medium properties (bulk), Altered surface properties (bump), Emissive properties, Main surface properties (BSDF)
Shaders: Defining Optical Behavior of Materials
A “shader” is a program/algorithm—a mathematical operation for managing optical properties of a surface such as reflection, glossiness, roughness, metalness, absorption, refraction, transparency, or light emittance.
BSDF: Achieving Physically Accurate Light Scattering
“BSDF” (Bidirectional Scattering Distribution Function) is a mathematical function that describes the optical properties of a surface. It is necessary to understand how materials interact with light.
Ocean™ incorporates BRDF and BSDF data to provide highly accurate material visualization. This capability is essential for industries where precise appearance prediction is a requirement to avoid costly physical prototyping and ensure product consistency.
Figure 3 - BSDF representation.
Textures: Enhancing surface realism with high-quality maps
“Textures” are made of pixels in a two dimensional (2D) representation. Textures are commonly pictures with pattern or photo representations. They can be generated procedurally. In computer language, a graphic image file is called “bitmap”, by extension texture file is called “map”. Common file types are JPG, PNG. They can be in full color but also as greyscale image in 8 or 16bits also with alpha channel (transparency).
See how it is possible to combine texture capture and spectral data to generate even more accurate material simulation with Ocean™.
Figure 4 - Examples of several texture maps : concrete, gradient, tiles, damage, noise.
Figure 5 - Example of a grid texture map applied on 3d models. (move mouse over the image to zoom in)
UV Mapping: Efficient Projection of Textures onto 3D Models
Applying a 2D texture map onto a 3D surface is called “mapping”. The coordinate system of 3D objects is based on 3 axis X Y Z, therefore its coordinate system in 2D for textures is based on U (X axis) and V (Y axis).
Texture UV mapping is the process of wrapping/projecting a two-dimensional (2D) texture/image/map to a 3D surface. For example, it is like applying a sticker onto a piece of Lego !
Figure 6 - Representation of the UV mapping of a cube. (Author: Zephyris from Wikipedia under CC-BT-SA-3.0).
Figure 7 - UV coordinates represent 2D positions on an object’s 3D surface. Selected red face on 3D model is represented as a red selection in UV coordinates. Values vary from 0 to 1.
Figure 8 - Example of bad UV unwrap and good one.
Advanced material properties in Ocean™ for industrial applications
Ocean™ provides advanced capabilities for defining how surfaces look and react with light or their environment. It is an essential tool for industrial materials simulation and applications in sectors such as architectural glass, automotive coatings, and high-performance plastics. The software supports following data:
(All rendered images are made with Ocean™)
Surface appearance
Diffuse map / Base color / Albedo map for realistic color representation.
It gives the first main appearance using color or pictures.
Figure 9 - Examples of pictures used as diffuse map for photo-realistic appearance on a sphere model.
Surface reaction to light and environment:
Adjustments to fine-tune surface reflection properties:
- IOR : index of reflection, how much the surface is reflective
- Specular : intensity of light reflection
- Glossy : amount/repartition of light reflection
- Rough : precision/blurriness of light reflection
Figure 10 - Examples of roughness and IOR variations.
Figure 11 - Example of a metal material : brushed anodized aluminium.
Surface alteration
- Bump : adds more details, gives the illusion (faking) of surface depth but it is still flat.
- Height : a variant of bump, alters the surface normal based on a height field.
- Normal : another method for bump, reacts much better with light and shadow.
- Displacement : affecting the topology of the geometry to deform it. Because it needs a more high mesh subdivision, it is much more realistic but can be heavy to manage.
Figures 12 and 13 are examples of various bump methods and their looking results :
Figure 12 (move mouse over image to zoom in)
Figure 13 (move mouse over image to zoom in)
Emissive properties
Emitters are materials that produce and radiate light, rather than just reflecting or transmitting it. The emissive properties define a material’s ability to generate its own light energy, contributing to the overall illumination of a scene. These properties combined with the global illumination capabilities of Ocean™ allows for simulating realistic lighting effects, such as glowing surfaces, self-illuminated objects, and ambient lighting sources.
A material with “emissive” properties are shown in the figure 14.
Figure 14 - Emissive materials
Volume properties
Also a material can have volume properties such as liquids, glasses …(Figure 15).
Here we add other layers of information such as volume properties into the material. We still can change its surface like previous properties (bump, emitter, bsdf).
Volume properties define how light interacts within a material’s internal structure rather than just its surface. These properties are essential for simulating materials such as liquids, glass, or translucent solids, where light scattering, absorption, and transmission occur throughout the material’s thickness. By utilising these properties, Ocean™’s bidirectional path tracing technology creates realistic depth and internal effects, particularly useful for transparent materials like glass and liquids.
Figure 15 - Demonstration of materials with volume properties
Quick Review: How to manage materials in Ocean™
Figure 16 - This is the default material used by Ocean™. A perfect diffuse Lambertian with a grey color defined by a number between 0 (black) and 1 (white).
Figure 17 - A material which light reflection is controlled by a Glossy shader, with a color driven by a uniform value and a roughness controlled by a Phong shader.
Figure 18 - Same material with a much more precise reflection because of a high Phong value in roughness. High Phong = smooth surface, low Phong = rough.
Figure 19 - Decreasing the IOR, meaning less reflection. Reflection is still precise.
Figure 20 - Adding bump texture map (grid image) to mimic the alteration of the surface. Surface is still flat.
Figure 21 - Perfect diffuse Lambertian material but with a texture map as diffuse instead of a uniform color.
Figure 22 - The volume emits light energy all over its surface. The diffuse is black and because of the energy power and temperature, we see the brightness.
Figure 23 - Metals don’t have diffusion. Their complex IOR defines the reflection color, driven by a “dielectric function”.
Figure 24 - A volume glass material. Here, some volume properties are driven by a Dielectric function.
Figure 25 - A dust, dirt and scratches image is used in a texture map for blending a reflective shader and a rough one. This image is also used as bump map for altering the surface, faking small notches and stripes.
Why Ocean™ is the preferred choice for industrial material simulation
Ocean™ stands out for its:
- Accurate optical performance optimization, reducing the need for physical prototyping.
- Seamless integration into engineering workflows for faster decision-making.
- Extensive material characterization capabilities for precise results.
Conclusion: Elevate your material simulations with Ocean™
In virtual 3D representations, the process of designing materials is very important and requires attention to detail. A simple 3D volume can become truly understandable because of its material properties.
Ocean™ allows the management of many material properties and shines in its use of very detailed physical models along with artistically-driven ones.
Many steps of CAD preparations are required before working in a rendering software such as Ocean™. A good understanding of what has to be represented is necessary. It is also about staging with scene layout, lighting, environment, point of view, a relevant mesh topology with enough detail, no errors, well sized, UV mapping projected efficiently on it. All this stuff is not an automatic process and needs expertise.
To go further
The articles below provide detailed insight of the main notions mentioned above:
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Q&A
What is industrial materials simulation?
Industrial materials simulation refers to the digital representation and analysis of material behavior under various conditions for industrial applications that require accurate prediction of optical and physical properties.
What is accurate optical characterization in material simulation?
Accurate optical characterization involves precise measurement and modeling of a material’s optical properties, such as reflectance, transmittance, absorption, scattering, and emissive behavior. This ensures realistic light interactions and reliable visual representation across various industrial applications.
How does Ocean™ help with material appearance prediction?
Ocean™ scientific rendering software integrates advanced algorithms and physical data to achieve material appearance prediction, allowing engineers to visualize how materials will look under different lighting and environmental conditions.
Why is the precise characterization of materials essential for accurate digital material simulation?
Precise characterization of materials is necessary to ensure accurate digital material simulation by incorporating real-world properties such as reflectance, transmittance, absorption, and scattering, defined among other parameters by the BSDF (Bidirectional Scattering Distribution Function). This allows engineers to achieve accurate optical characterization and material appearance prediction, minimizing discrepancies between virtual models and physical prototypes.
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