Learn about mapping Bifrost channel data to shading attributes.
- [Narrator] In the following exercises, we use bifrost channel data, to mask, two Arnold materials. If you're mental array, you'll use different nodes, which I covered another course, Mara 2016, bifrost fluids. But the concept is the same. We're extracting multiple channels of data, and combining them, to build a mask. To begin, let's visualize the raw channel data, on the meshed voxels of the shape node. I've prepared a scene that has the building blocks ready.
There are two versions of water we'll be using. Clear, and white water. The white water has a lot of sub-surface scattering, to give the effect of foaming bubbles. Any channels that we wish to use, in a shader network, must me manually exported from the shape node. Let's go into that shape node, open up bifrost liquid one, and select liquid one. Which is the bifrost shape node. And in the Arnold attributes, we need to type the channels to export here, in the channels field.
Vorticity is already entered in for us, by default. Click at the end of that word, and tap a space bar to add a space, and type in velocity, then another space, and churn. Press the enter key, and now those channels will be available in the shading network. The liquid has an AI Utility shader applied, for fast testing. Let's check it out in the Arnold render view. Go to the Arnold menu, and choose render. When it's finished rendering, press the stop button, and create a snapshot.
With the liquid one node, still selected, open up the hypershape. I'm going to strip down the interface here, to create more space for my graph. The material viewer, will not be helpful, in visualizing channel data, so I can close that. The property editor is redundant, to the attribute editor. And I prefer to use the attribute editor, so that I can switch back and forth between shape node, and shading note attributes. I'll close the property editor. And I can use the search engine, to create nodes in the graphs, so I don't really need the create panel over here, either.
I'll close that too. All I really need, are the graph and the browser. In the graph toolbar, click on the button, to graph materials, on the selected objects. Test AI Utility, is the current surface shader. Let's create a new node for the bifrost channel. In the graph, press the tab key, and type in A-I-U, and we see a bunch of AI user nodes. We want the aiUserDataFloat.
This is going to be a single floating point number, for churn. In that node's attributes, we have to once again, type in the name of the channel. Click in the attribute field, and type in churn, press enter. Let's also rename the node, to keep things clean. Select that and copy paste it, into name up here, and underscore. Now, we need to make the connections, to the shader. I'll just move these nodes around, to stage them. The data float node, is of course, a floating point number.
But the aiUtility color, is expecting RGB. Open up the color selection, and connect the out value, to color R. Color G, and color B. With those connections made, we can do another test render in Arnold. Close the hypershade. And in the Arnold render view, press the play button. And now we see the churn, applied as a greyscale value, on the surface. Press stop. And make another snapshot.
That's how to use a aiUserdata node, to apply bifrost channel data, in an Arnold shading network.
- Bifröst basics
- Analyzing the node structure
- Emitting from a polygon mesh
- Colliding with a polygon mesh
- Adding velocity, friction, and drag with motion fields
- Optimizing space and time accuracy
- Caching simulations
- Meshing and exporting liquids
- Render-time meshing in Arnold
- Applying channel data to Arnold shaders
- Generating foam from a liquid
- Rendering and shading foam in Arnold