![]() ![]() Create a new PrmanShadingNode and set the node type to PxrDirt. PxrDirt is an occlusion shader which allows us shading effects affected by the local topology in the geometry (i.e. We could accomplish this using textures but instead we make use of the PxrDirt node to control where the patina and metal are seen. This layer will completely cover the Base layer until we add an input to Layer 1 Mask. The previous bump pattern is used again in this layer to be consistent but you could actually use a different one here to really improve the realism. We've added a PxrFractal and a bump pattern to increase the realism. The patina shading is a diffuse color is sampled from a real image with some diffuse roughness to help bring out the "powdery" look from the patina crust. Note that you may have to re-enable Layer 1 if you had disabled it while working on the base layer. Create another PxrLayer node and connect its pxrMaterialOut output port to the Layer 1 input port of your PxrLayerMixer. The Patina will be our "Layer 1", sitting on top of the base layer. The settings are somewhat arbitrary since they are art directed, but we're looking for an older dull copper or bronze look: To approximate a copper material we set the diffuse and specular then add some procedural bump so the copper has a nice texture to it. Create a PxrLayer and connect its pxrMaterialOut port to the Base Layer input port of the PxrLayerMixer. The Copper/Bronze will be our "base" layer. For this example we're just using two layers, the Base and Layer 1. This is great if you want to reuse networks somewhere else. Note you can connect other PxrLayerMixers into the layers for using collections of looks and masking them together. We will focus on building our base layer first so let's disable Layer 1 until we wire our patina layer in. If a layer is enabled but not connected the entire render will go black. Note that Layer 1 is enabled by default with the assumption being that there will usually be at least two layers coming in to the PxrLayerMixer. There is a BaseLayer plus four other layers, numbered 1-4. Let's take a look at the default state of a PxrLayerMixer shading node: This sets up the node where we will be connecting all the layers. A patina, a diffuse layer that's a bit crusty and blue-green in colorĬreate a PxrLayerMixerand connect its out port to the inputMaterial port of the PxrLayerSurface.Two basic layers of materials are needed: Another method for creating a patina is to use vinegar and salt to create a crust on the metal, which is the look we'll experiment with here. ![]() For example, heating a metal to produce different colors could be replicated using the iridescence attributes in PxrLayerSurface. Depending on the look you are aiming for the layout of the materials will vary. In researching the creation of a patina on copper or other metal you will find it is a multi-stage project which can involve a variety of methods. Layer-specific attributes such as color and texture come from upstream materlal(s) connected into the inputMaterial attribute.įrom here planning is very important to avoid duplicating work and making your material network as simple and useful as possible. PxrLayerSurface contains only global attributes which would apply to all layers. The reason for this is that PxrLayerSurface is designed as the Bxdf on top of which layers of patterns are combined. This is the framework that will inform RenderMan which materials will be rendered for the assigned object (new nodes are colored with red):Īt this point you could render with our new shading network but there's not much you can do with this material on its own this node has a limited set of attributes. Step 1: PxrLayerSurfaceĬreate a shading network and assign a PxrLayerSurface Bxdf to your object. The scene is renderable at this point, however we have no materials assigned to the statue so it will render with RenderMan's default Bxdf shader: PxrDiffuse. Load the layeredMaterial_prep.katana tutorial scene which contains the framework for loading the statue geometry, a ground plane and spot lights. At the bottom of this tutorial you can find a Katana scene to download with the parts necessary to reproduce this image. This means effects like car paint, labels on bottles, dirt or mud, can all be layered efficiently for rendering.īelow you can find a step by step example of creating a patina on a bronze statue. RenderMan allows for creating complex looks through layering materials.
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