From the course: 3ds Max 2019: Advanced Materials

Setting a custom reflectance function - 3ds Max Tutorial

From the course: 3ds Max 2019: Advanced Materials

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Setting a custom reflectance function

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- There are a couple other ways that we can adjust the balance of specular reflections. We can adjust the Metalness parameter. Remember that if it's a value of one, then we're using the Pure Metal shader, and if it's a value of zero we're using the Pure Diffuse shader, which includes things like Transparency and Sub-Surface Scattering. But we can adjust the value fractionally, to achieve a balance between those two shaders. And this is a recommended technique for adding a little bit of life or realism to a metal. Just give it a little bit of diffuse component, set the Metalness to point nine. And then immediately we see that we're getting a bit more shading on that surface. That's a good technique that doesn't deviate too much from physical realism. If we bring it down to point five we'll get a 50-50 split between those two shaders, and that will be a more dramatic example. We're seeing now a lot of diffuse shading on that surface. The other way that we can adjust reflections is by directly changing the function curve. And that is going to be a nonphysical effect, and in order to access it we need to be in Material Mode, Advanced. I'll set Metalness back to one, and start playing around with Advanced Reflectance Parameters down here. When a Physical Material is in Standard mode, we won't see this Advanced Reflectance Parameters and the bidirectional reflectance distribution function, or B-R-D-F, will be determined by the index of refraction. And B-R-D-F is just a fancy word for this relationship between the Facing and the Edge polygons. Remember, facing is the flat surfaces and edge are the surfaces pointed 90 degrees away from the camera. So if you're in Standard mode, then you're always locked to the I-O-R, but if you're in Advanced mode you have the ability to go into Custom Curve. And now we've left the strict confines of the physical simulation and we can have a more art-directed look. We can give it an impressionistic look, making the highlights pop, for example. And that can be done simply by increasing the Facing amount, let's give it a little bit, let's say point two. And immediately we see much stronger highlights because now the facing surfaces are returning more of this reflection color. And again, if we want it to be a gold material, we probably want a colored reflection. I'm just going to drag and drop from the Base Color onto the Reflections Color and choose Copy. And now we've got nice strong gold highlights almost everywhere on the model. If we want a purely linear response here, set the Facing value to zero, the Edge value to one, and the Slope to zero point five five. And now we've got a straight line curve, in which the relationship between the facing angle is purely linear. And that's how to achieve a custom reflectance function in the Physical Material.

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