Vellum Workflow Tips

Blog Entry #4. December 30th, 2019

Hi there. In a previous article, I talked about how to improve your workflow in Houdini. I gave an example of a rendering, lighting, and modeling workflow, but what about a vellum oriented one? Vellum is one of the more challenging elements in Houdini, and everyone has a different approach for every project they make with it. However, trying to start out and build an individual project, especially when you are a beginner can be difficult. So I thought it might be fun to try and create a blueprint for where to start for vellum.

Let use the modeling approach I mentioned in my first article to start. This will be a good stepping stone for our process going forward.

The Modeling Approach:

#1 Define

#2 Analyze

#3 Generalize

#4 Dependencies

#5 Abstraction

#6 Parameterization

#7 Randomization

#8 Technical

#9 Maintenance

#10 Style

So let's take this and make it Vellum Themed!

The Vellum Approach 

#1 Define

  • What do we want to create? Clothing? Sand? Balloons popping? We need to decide this here. For example, let's say we are making a cape on animated character.

#2 Analyze

  • Is there any easy ways to approach this? We know we'll be using Vellum Cloth. But will Vellum Drape work better? Will the cape tear off our character and float away? Can we use Edge Fracture to tear the cape, or will we need to draw a curve on the cape to fracture? There is a lot of questions we need to answer here. Go digging for some tutorials. Also, take some time to memorize some hotkeys.

#3 Generalize

  • What is the easiest way to build a cape? Can we just start with a grid and some point groups, or can we find a model online? Instead of creating attributes such as weld for our solver to handle, or writing some VEX in a wrangle, can we just activate that from Vellum Constraints, or solvers instead? Plus, consider which routes will get you the best results.

#4 Dependencies

  • Look for reference. What does an actual cape look like in real life? Also, take some time to consider how different fabrics react to different forces. Whether that be wind, the character interacting with the cape, or external collisions.

#5 Abstraction

  • Is there any forces we don't need or will interfere with the look of our cape simulation? As a VFX artist we need to aim for realism, but sometimes real world forces don't translate into 3D space so well. Same goes vice versa. Can we add more wind, or trail our velocity more? 

#6 Parameterization

  • Now double check that our vellum simulation hasn't gone too far. Double check to make sure the forces are believable, and that the forces aren't causing the cloth to intersect and overlap. Find the best settings for your cloth now.

#7 Randomization

  • Can we randomize the fractures of our cloth by using using an attribute noise SOP, or start to create and layer attributes to create more diverse appearances of the cloth? Is there any parameters we can animate for a smoother look?

#8 Technical

  • Do you need VEX to solve your problems? Instead of using the default Vellum Solver, do do you need to create a DOP net with forces that you can apply after your post processing? Will we need a Vellum Post Process Node to smooth out our cloth?

#9 Maintenance

  • Label your changes, and keep track of them. The last thing we need is a messy and disorganized Vellum simulation. Adding notes in your file can help if you need someone else to look at it. Or if you need to put it away for a period of time. Keep your file organized.

#10 Style

  • Finally, after working with Vellum for a long period of time you'll start to develop your style of how you'll approach projects. You'll create a greater understanding of how Vellum works, and you'll need to use tutorials less. Your projects will look better, and your own workflow will develop.

Have Fun!

Useful Vellum Hotkeys/Useful Hotkeys in General

  • O: Orthographic/ perspective

  • N: Select

  • Shift + Click : distributes connecting wires from different nodes together. Useful if you are operating with nodes that have multiple outputs.

  • Shift + Enter: Wires nodes with multiple outputs together.

  • L: Lays out and organizes nodes in the network view.

  • Space + G: Orients your viewing back to the center of the view-port.

  • B + Cursor: Turn on bypass flag

  • E: Drop on wire

  • F: Focus - pans and zooms

  • A: Select all

  • U: Jump up out of network

  • W: Open spreadsheet

  • S: Suspend all render jobs

  • Shift + K: Kill all  render jobs

Tip: Switching to the Technical Build can help you decrease your time flipping back and forth from the geometry spreadsheet.