Example - Logo rezzing up
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Introduction
For this simple example, we are going to convert a blob of polygonal material into the LightWave logo. We'll start by adding a LightWave logo to our scene. If you don't have one to hand, here you go - New_LW_Logo_v001.7z
download - it only needs to be in the scene for this effect, so you can move it out of sight, scale it, just hide it from rendering and make it invisible in OpenGL. Our result will not be affected.
Steps
Add a null to the scene. We'll call ours "Volume_Logo." In the Object Properties window, go to Primitive > Geometry > Object Replacement and choose OpenVDB Evaluator.
Click Properties in the Object Properties window to open the Node Editor. In the Node Editor window we see that the destination is OpenVDB and that its input is Grid. If you can, try to keep the Object Properties window open throughout this Example and visible because it will be interesting to see how it changes.
Moving the Node Editor window so you can still see OpenGL and the Object Properties window, go to the OpenVDB group and add the Mesh To Volume node. Double-click the node and in the window that appears, choose your New_LW_Logo_v001 object as the Target Mesh and change the Type to Level Set. Pipe the Grid output to the Destination node. You should see a blobby object that looks something like our LightWave logo, but we need to increase the resolution to see it properly.
To change the value over time, we will add a Constant > Scalar node and hook it to the Voxel Size input on our Mesh to Volume node. The Scalar node's default value is 1.0, so your blob becomes a small block with six polygons (a parallelepiped). You can change the Scalar's value down to what it was initially - 0.05 - or you can go a bit smaller to see the logo really develop.
If you set the Size to 0.45, you will still get a six-sided block, but it will be bigger. Create a key at the other end of the timeline and make it 0.002 and you should see your logo take shape and improve its resolution over the course of the scene.
Result
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You can use an OpenVDB object made like this as a dummy object to stand-in for a high-resolution model that slows down your scene. Save out the Volume_logo on the frame you like to get a lower resolution version to be switched out for the full-resolution object at render time.
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Contributed by Richard Feeney