How I created a festive animation with iClone BuildingGen, Character Creator and Houdini

Project Henshin! (変身!) is my artistic and metaphorical transformation, representing my exciting leap from Cinema 4D to the captivating world of Houdini. 'Henshin', a beloved term in Japanese anime for initiating electrifying transformation scenes, fittingly translates to 'transformation'.

In this project, I blend the pulse of modern dance with the grandeur of Gothic fashion and architecture together with Reallusion’s iClone BuildingGen Plugin. Inspired by the vibrant and whimsical dance scenes in anime, I sought to capture that same energy and playfulness in Henshin!. In this article, I will outline my workflow, highlighting the key takeaways and challenges I faced during this project. I will also share valuable resources, including articles and tutorial links that helped me troubleshoot and ultimately achieve my desired outcome.

Festive Character Animation with iClone BuildingGen, Character Creator and Houdini - YouTube

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Environment modelling

Throughout the project, I typically adopt a hybrid procedural setup for efficiency. For instance, the altar arch-shaped screen begins with curves drawn in Rhino by tracing a reference image. Since Houdini's curve drawing utilities are relatively primitive compared to Rhino, I prefer to do any line or curve drawings in Rhino first. This included the backbone curves of the altar screens as well as the profile/section curves. Later, I bring them into Houdini either as FBX (planar mesh) or IGES (NURBs curves).

In Houdini, I utilised a Sweep node with imported backbone curves and profile curves to create the main arch. Subsequently, I added more intricacies by manipulating the same backbone curves with Soft Transform and Transform’nodes. Then, I used Copy to Points to duplicate them geometrically, using the arch shape as the foundation. (Adrien Lambert has a great tutorial on Gumroad that covers all the basics of procedural modelling.)

Assembly, look-dev and shot-framing

When working on materials or shaders, I always prefer to work in context – viewing through the final animation’s camera, with appropriate lighting and environment settings – rather than isolating different objects. This approach ensures that I focus my efforts on objects and materials most visible on camera.

To maintain a relatively mysterious atmosphere throughout the animation, I emphasise bottom-up artificial lighting. A major part of the look-dev process involved testing the placement of bottom-up light sources to enrich the scene. Here, Reallusion’s French Style BuildingGen Content Pack proved invaluable. This pack includes nine variations of detailed houses, optimised with minimal point counts and baked textures.

Adoption of BuildingGen & French Style House content pack

Using iClone’s BuildingGen plugin, I exported all the French Style BuildingGen presets into FBX format. I then imported them into Houdini using a simple drag-and-drop method, facilitated by the Houdini plugin ODTools. ODTools automatically created a Material network with all the materials exported from BuildingGen, allowing me to easily drag and drop the building textures into the network.

I separated randomly selected windows as Redshift Mesh Lights and scaled the buildings down to knee-size models, effectively turning them into miniature floor lanterns. I scattered points on the ground and placed the nine variations of the French Style buildings onto these points using an ‘Instance’ object. This method added significant visual detail and provided fantastical direct light to the scene without overwhelming global illumination.

Character

Character Animation in iClone

My character workflow began in Character Creator, where I primarily used the body morph sliders and Skingen to create my two characters. I then brought the characters into iClone and explored the Actorcore library for mocap animations. I chose five sets of Actorcore Motions and blended them into three sets of character animations.

The Edit Motion Layer and Motion Correction functions in iClone were the ones I used most frequently. Edit Motion Layer allows me to manually keyframe character movements with IK joints, while Motion Correction helps me fix foot sliding.

I always set the first frame as a T-pose or A-pose, with at least 15 frames of buffer before the character animation starts.

Once I was happy with the character animation, I exported it from iClone as both Alembic and FBX files for use in Houdini and Marvelous Designer.

Cloth Preparation

The character clothes are prepared separately in Marvelous Designer using the first frame of the exported Alembic file from iClone. Once I have the garments fitted to the character’s A-pose, I re-topologized them as quad mesh and then export them as OBJ files into Houdini.

Vellum Simulation in Houdini

With both the character animation and garment A-pose imported into Houdini, I first performed a Vellum simulation solely on the main character's body, with the armpits masked out to solve intersecting frames. This simulation resolves skin intersections and prevents future issues down the line.

This workflow is also outlined in detail on SideFX’s site: Vellum Cloth: Tips & Tricks.

I manually painted masks on the cloth to define which parts of the clothing should 'stick' to the animated character at all times. I then used a 'Point Deform' to deform the static clothing to the animated character.

For simulating multilayered clothes, I always do test simulations separately before bringing them together either through a 'Vellum pack-unpack' workflow or by combining them into a single stream. I personally prefer setting up multilayered cloth simulations within a single stream, as I find it much clearer to read and easier to attach different cloth parts together when necessary. For instance, I attached the jacket sleeves to the shirt sleeves to ensure that the jacket does not slide down the character's arm when her arm is lifted.

With all the simulations cached, I use a Point Deform node to transfer the simulation from a low-res/triangular mesh to a renderable/quad mesh.

Cloth Transformation

The cloth transformation is primarily a disintegration effect, which can be easily achieved with a SOP solver.

Applied Houdini - Particle IV covers the fundamentals of Sop Solver in great detail, which I highly recommend everyone learning Houdini to go through:

I then perform a Pyro simulation on the disintegrating clothing. The resulting pyro simulation is then fed into a Pop simulation to generate swarming particles onto which I instanced butterflies. The butterfly swarm consists of nine time-shifted variations of the same butterfly animation.

Rendering

Coming from Cinema 4D, what tripped me up rendering in Houdini was object organisation and motion blur. Managing objects in the OBJ context can quickly get messy – unlike LOPs where everything is node-based and has to be interconnected, everything in OBJ is loosely positioned. I used Bundles to manage my OBJ render sets in Houdini OBJ Redshift; this allows me to render and debug objects separately whenever necessary.

To render characters with correct motion blur, I enabled the Deformation Blur option under Redshift ROP. Using a Trail SOP, I calculated the characters’ velocity and transferred this velocity to all the clothing using Attribute Transfer. Without this step, I noticed that at higher Deformation Blur settings, the characters’ skin would pierce through the clothing.

Afterthoughts

Transitioning to Houdini has opened up numerous possibilities for both my personal and professional work. The number of iterations this project required to reach the final result would have been impossible without a procedural setup. Houdini's fully procedural nature enables me to very quickly update files exported from iClone, Marvelous Designer or Rhino. In my early days of using Houdini, its procedural nature could quickly turn a fun artistic project into a technical nightmare, diverting my focus from achieving the render to getting lost in optimisation rabbit holes. If you are also exploring the abilities of Houdini and the other animation tools I used, here’s a more detailed behind-the-scenes.

Despite all the technical hurdles, Henshin! represents a significant personal milestone, a thematic and technical transformation that has profoundly shaped my approach to future projects.