10 simple steps for rendering in V-Ray 5 for SketchUp. Part 4 of 10

V-Ray-Render-Illustration.-040

Make Materials

🚩 In everyday life, we intuitively read environments and sense the effect lights have on it. But rarely do we sit down to create a material from scratch. Making good render materials takes dedication. It is a complex subject. Here, we will make do with a few quick tips. Fortunately, there are many shortcuts.

👨‍🎓 Note that in this step in particular, instructions are more specific and technical.

⚡ For immediate results, use the renderer’s built-in materials.

💡 Begin with the material closest to what you want, and tweak it subtly as needed. Don’t try turning plastic into gold. 

⚡ Tweak just one material property at a time, and evaluate incessantly. 

💡 This helps understand how materials work. The basic properties are diffuse, reflection, glossiness, and bump. Once you can predict what adjusting a certain parameter will do to the material’s appearance, it is time to explore more advanced parameters. 

⚡ Evaluate your materials applied to objects with varied, curving features. Evaluate your materials in broad sunlight in an environment with distinct features that interact with the material’s surface.

💡 In low lighting, thick fog and other occluding effects, everything looks kind of good, because what you see is your own imagination, not the object. Instead of hiding bad materials with obscure lighting, be frank and sober with your subject. 

 V-Ray’s live preview swatch is too small. To properly assess materials, instead do test renders in the VFB and interactive mode. Raise the frame buffer’s default height resolution to perhaps 1080 pixels, and zoom in aggressively on the object, so it nearly fills the window.

A complex model can easily contain hundreds of materials. The fastest way to find a particular material is to use the paint bucket and sample it from an object in the Sketchup viewport. V-Ray will then automatically select it in the asset editor.

A good material can represent a lot of work. Make it a habit to prefer creating a few good materials, and reuse and refine them throughout your projects. Keep your asset filepaths permanent.

⚡ Use bump to simulate rounded edges without modifying geometry.

A classic tip for materials is to add a new bump layer, set its mode to Bump texture channel, and here plug in the bitmap function Edges. This works best for small-scale effects.

⚡ To control the scale of a material, simply edit its texture width in Sketchup’s Materials panel.

💡 Native Sketchup allows projecting – uv mapping – materials on only one face at a time. For complex shapes, this does not suffice. But V-Ray provides good help. Use V-Ray’s built-in triplanar projection as a quick way to map seamless materials to objects. Just right-click on a Sketchup selection and pick V-Ray UV Tools Triplanar Projection (World). Triplanar mapping will apply assigned materials to all innermost faces and map them by face orientation. This often gives acceptable results.

If you need full custom texture mapping control, use an extension like Wrap-R or a standalone application like Substance Painter.

Materials’ size and position per face are controlled by what in Sketchup is called texture orientation, more generally known as face uv:s. Note that Sketchup’s paint bucket tool not only applies a material, it also resets the target’s existing face uv:s. Typically, this is too destructive. But there are some tricks to bypass it.  

⚡ To replace faces’ materials while keeping their current uv:s intact, first select faces in Sketchup’s viewport, then click Sketchup’s Entity info panel’s material swatch, then from the Choose paint dialogue simply pick another material. 

💡 You can simultaneously replace multiple source face materials to one target face material. 

You can also select all faces with a certain material in a context simply by right-clicking a face with that material, then picking Select → All with same material. Again, use Entity info’s material swatch to swap your selection’s materials while retaining their texture orientation.

⚡ To replace all instances of a material with another, open V-Ray’s asset editor’s materials list, right-click a source material and pick Use as replacement; next find the target material in the same list and right-click it and pick Replace in scene.💡 If you have an artistic vision and know what you want, the few hundred built-in materials most renderers ship with will very soon be too limited. There are many rendering applications

with different workflows and material definitions. This why materials are often exchanged in the form of collections of texture maps. The most used maps are diffuse or albedo, roughness or gloss, and bump or normal. There are many more. While maps alone cannot emulate all subtleties of a material, they still cover many common use cases and have thus become a kind of de facto industry standard. To find maps for recreating materials in V-Ray, use a provider of high-quality material maps. For this render, we have employed materials from Megascans and Poliigon and other sources.

💡 A key to creating realistic materials is making them look worn, heterogenous, grimy, or, more precisely, in a particular state of history. Computer graphics, however, have since their inception been prejudiced to prefer simple, boxy shapes clad in synthetic, repetitive materials. While simpler to program and faster to execute, such output quickly betrays its digital origin. 

With some resolve, it is fully possible to give any material a worn, varied and organic feel. One of the ways to do this in V-Ray is with a blend material. 

For this, you need three materials. First, start with any base material, which will represent the innermost surface to be seen – it may look worn already, or pristine and new.

Second, make a top material which will represent the dirt layer above. This should be based on a texture that shows directional leakage, or irregular splats or abstract grime, typically dark, on a background that is otherwise all transparent.

Here, it is important to use a seamless and high-resolution texture and to make the material size larger than the largest visible surface span it will be applied to, so as to avoid repetition. Fitting textures, or starting points for making them yourself using basic photo editing skills, can be found at quality texture sources and are typically called something like leakage or grunge.

Third, create a new blend material, and assign the base material to the base slot and the dirt material to the coat slot. Use the coat slot’s blend slider to fade between a subtle patina and rich, deep grime. You can then reuse the same dirt material in many different blend materials. 

This technique was applied on hundreds of surfaces in our render, above.

💡 More than anything else, it is materials make or break your render. Take care when creating materials. If starting your material library from scratch, it is not unusual that making materials takes longer than all other rendering tasks combined. Give it your time and pay attention, and you will succeed.

🌤 Next week we’ll shine. Let’s light up our scene!

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