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Recreating A Large-Scale 2D Environment In 3D With Houdini and Nuke

CG Artist Julien Rollin walked us through the Countryside project featuring the Maya to Houdini to Guerilla Render pipeline, talked about the importance of having a slap comp, explained in detail the assembling and rendering workflows, and shared a lot of learning resources for other environment artists.

Julien Rollin is an Environment Artist currently studying at a small French CG school called Creative Seeds as a third-year student. Seven months ago, we had the opportunity to ask him to share a breakdown of his very first environment practice using Houdini and Arnold in a project called Afternoon Fishing. To learn about his second project Countryside, we spoke to Julien again, who gladly shared a ton of new techniques and workflows he learned along the way and shared some tips to avoid making some of the mistakes he's made.

When asked about the inspiration and reference-gathering stage, Julien explained he had to find a good concept art, ideally large scale, since he wanted to tackle a bigger challenge than his first environment. Luckily, one of his favorite artists, Grady Frederick, posted a very cool concept just a few days prior:

"My first environment was simple workflow-wise, as I knew almost nothing about the environment, which means as little software as possible: blocking in Maya, scattering & rendering with Houdini/Arnold, composing in Nuke, and voilà.  

As this project was a school assignment as part of a module practice to discover Maya to Houdini to Guerilla Render workflow with instancing, which I'll detail later, it was quite different to work with scattering. This workflow is much lighter and more flexible, and you can render millions of instances easily."

Speaking about planning the composition, Julien revealed, that he did a basic modeling of the main mountains, foreground hill, house, and rocks to find the right scale for his scene. A lot of time was spent on refining the mountain distance since it was crucial to get the right sense of scale. He also shared some useful advice and resources on reference-gathering for beginners:

"Like every project I do, a good main reference is really important. The key to getting a good result, especially coming from a 2D concept is to gather as many references as possible. It helps with the composition, lighting, and mood. The other references are real-life photos to help achieve the realism where you need to match reality. If you want to learn more about reference usefulness, I highly recommend you visit this blog."

Julien said, that he already knew that he would have some challenges with scattering to create the right sense of scale and had to make some changes to the concept:

"For example, the trees in the concept are way off, they are 100-200 meters of distance from the house, but their scale is still huge, which doesn't make sense. So I had to make some changes to make the scene plausible. The top part of the concept was a challenge too. I've tried to interpret as best I could, so I made my mountain shapes based on various references and my own interpretation."

The texturing for the ground was done using texture projection based on Google Maps satellite and Textures.com photos. For the foreground, Julien tried to optimize the texel density and details, so he separated the FG terrain into 2 parts and then started projecting and stitching the textures. As for the background part, he localized a few areas in Scotland and did the same thing by hand to follow some guides he painted. It added a nice realism touch that was difficult to achieve otherwise.

The plants used in the scene were made with a tool called YL Atlas Cutter by Julien's friend, Yoann Leong, which is available on Gumroad. It allows you to cut out the Opacity Maps on the low LOD models to get full geometry, without the pain of Opacity Maps for offline rendering.

For the technical aspect of the scattering, the foreground has been done with standard scattering, using attributes from the maps to use the road as a density mask. As for the background part, it was done with curve-based scattering. Julien explained that it was easy to add rows of trees and bushes by simply drawing curves onto the terrain, and this way, he was able to control exactly how he wanted the rows to look. The rest was done using basic scattering like the FG with Attribute Paint to create the forest.

"During quite some time on this project, my overall scene scale felt off, not only because of my actual vegetation scale but also because I was missing all the volumes and darkness to match my reference. What helped me a lot, and I wish I would have started it sooner, was 'slap comp'. If you don't know what this is, this is basically creating a very rough initial composite that is used to test and visualize the final output. In a way, you can also secure your actual progress with a final look and see if you're on the right track! 

In my case, this means: adding a sky, volume, basic color grading, and lens effect. My perception drastically changed, and I knew what to focus on first (in other words, the things that were the most shocking to the eye at first look). I was messing around with a bit of everything in the scene changing mountain shape, tree rows, etc., but it was more details than important changesWith this slap comp, I've focused on the most important parts, so I've been drastically faster.

I've started the compositing part a bit late, I'm pretty sure if I had started it earlier, I could have figured out the scale problem before."

We also asked Julien about the workflow behind the stone building setup and requested to describe this process for beginners:

"The stone building was a combination of hard surface modeling and procedural setup inside Houdini. It was my first time making a procedural build like this, the cgside YouTube channel helped me a lot to understand the basics and get a nice result. 

The process is simple, I've selected each wall, created a bounding box of the actual volume, taken each edge of the box, added jitter on the curves, fractured it, and added a bunch of little randomizations for rotation, scale, and damage. You can grab the scene file for free on my Gumroad.

Once the modeling was done, I unwrapped everything in Maya using Unwrella 4 plug-in, did texturing in Substance 3D Painter, and was done! Since the distance is far from the camera, I was able to not put too much work into the texturing part, even though I've remade it a few times to get it to match the original concept color values."

Moving on to the process of assembling the scene, Julien revealed that overall it was a bit back and forth over the progress of the project. The fun part was to add extra detail to the scene that wasn't on the original concept art, however, he wasn't able to add as many sheep as he wanted since those in the FG needed too much extra work with the groom and sculpt. The sheep in the right part are stock footage.

"To add these extra props, I've used some on Megascan and a lot from Polycam. The Polycam public library is absolutely insane and covers everything you need for BG elements. The caste is from here as well as the sheep, a few trunks, props around houses, and more. I highly recommend you check it out, it's a huge time saver.

For the final compositing and final touches, everything has been done in Nuke. My Node Graph is a bit overkill ahah but I've learned a lot of techniques this way.

My main concern was to add the right saturation/color on the grass to get the same look as the concept, as well as add color variations on top. I achieved that using the handy Nuke Gizmo called PointPositionMask. By exporting a world position pass, you can select a zone as a mask, which is quite handy. This way I was able to control different zones very easily. The rest was done with 3D tools inside Nuke to add sky, volume, and birds. 

The volume part was fully made in comp, which means that I have 100% control over it. It has been made with the Tx_Fog Gizmo by Thomas Lefebvre. With a simple deep expression, I could limit the atmosphere distance as I like."

As for the final scene rendering, it was done inside Guerilla Render. In Julien's opinion, the UI of this software seems a bit outdated compared to others, but it's really powerful and the logic behind it is wonderful, it has also a robust and impressively fast renderer with the best interactivity he's ever seen.

"To get into more details about the assembly of this scene, I've imported my geometry as a set, linked all the textures, and imported my scatter using instancing.

Basically what I do is that I export my point cloud as Alembic with all the necessary attributes, I link it inside Guerilla with a Scatter node, with all my actual plant geometry, and done. The lighting setup is pretty simple, I've used a light blocker and a spot light to create this intense sunlight coming onto the houses. I've used an HDRI to create a few lighting bounces in the background and this is it."

In conclusion, Julien disclosed that this project took him about 2 and a half months of work and talked a bit about the making of Countryside in retrospect:

"While I think my biggest challenge was remaking over and over some parts, like the rocks on the FG, and distance/scale issue, most of them could have been avoided if I had done a slap comp earlier, in a way to secure the 'final' output of the project. Lesson learned! 

Something else I could tell anyone studying CGI is that it's difficult to have artistic and technical skills at the same time when you're learning, that's why you must free yourself from one or the other. So, grab as many high-quality references as you can!"

If you want to learn more about environment workflows with Houdini, he highly recommends checking out these YouTube channels which were a huge help to him: Nine Between, cgside, Adrien Lambert, and Inside The Mind. As for lighting/colors, you can visit these fantastic blogs: CG Cinematography and SKIENTIA.

Julien also encourages other artists to reach out to him for questions or feedback via Instagram or other social media.

Julien Rollin, CG Artist

Interview conducted by Theodore McKenzie

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Comments 1

  • Anonymous user

    Cool work!


    Anonymous user

    ·a month ago·

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