Tutorials
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Creating Sorindar, the Gray Rock...
December 05, 2024
Created and written by Johnny Fehr. Modeling by Clément Béziers.
Edited by Leif Pedersen
After finding Clément Béziers' wonderful work, I decided to reach out to take his model for a personal creative spin in Mari and RenderMan for Houdini … and the 3D community never disappoints … as Clément Béziers didn't hesitate for a second to get excited about the creative collaboration!
Let's break down some of the key look development processes with Mari and Industrial Light & Magic's awesome material layering system, MaterialX Lama.
Clement gave me a high and low poly model, from which I adjusted the UVs a bit and split them into UDIMs to get more texture resolution. This allows me to use several 4K maps, instead of a single 16K or 32K texture map. The former is easier to parallelize and makes creative workflows much more efficient.
More UV tiles equals more efficient resolution
In zbrush I subdivided the low poly model, and then projected the high poly details onto it, which allowed me to export high quality displacement maps rich in fine detail without having to deal with the expensive high polygonal model in my 3D app.
TIPS
1. When projecting high poly details in zbrush, always do one subdivision step at a time and not all at once.
2. When mirroring the UVs, you can copy > paste UV patches in Mari.
For secondary displacement details, I used texturing.xyz textures and added tileable textures for the dragons’s hard surface sections. After this step, my first course of action was to test the setup in RenderMan for Houdini to make sure my choices were successful so far.
Levels of displacement refinement
I really love starting a displacement network with a pxrDisplacementLayer node, as it makes the layering of displacement maps super efficient and straightforward.
After that I went back to Mari and started with large swaths of colors, as things developed, I added finer details and breakups with the help of geometry bakes. I finished things off with high resolution tileable textures and some hand painting.
Layering in texturing from base colors to fine detail
Another round of RenderMan testing was useful at this stage and allowed me to build the material networks in manageable steps. Once I felt happy with my progress, I made supporting material texture maps, such as Roughness and SSS scale, plus arbitrary masks for control later on in the look development process.
TIPS
1. Start simple and layer in detail as you take a look at the references to see how your asset is colored.
2. With geometry bakes you can quickly bring many parts into your textures and thus support the shape and remain procedural at the same time.
I am an absolute fan of MaterialX LAMA, because it allows me to create flexible shading networks with efficiency. I’m always looking to be as resourceful as possible and only adding material lobes when necessary, really helps keep shading costs down.
A good place to start your material is with a clay render of Subsurface Scattering, which makes dialing in this subtle effect much more effective without texture details.
Clay renders are a great way to see fine detail clearly
With the help of our arbitrary texture masks, I made color corrections for different parts with pxrLayeredBlend nodes. I also graded the Roughness map to have full control over the different values and areas, as animals in nature tend to use harder surfaces in their body for defense, thus wear and tear needs to be expressed with that in mind.
MaterialX Lama allows for extensive and non-destructive layered shading
Another important texture detail is dirt … especially with a dragon! I was able to accomplish this effect with a new set of textures which are then layered over the base dragon material with a LAMA layer or LAMA mix. I then use masks in these material layers to isolate the location of the dirt textures, giving me a lot of non-destructive editing capabilities during the look development process.
Layering dirt textures is crucial for added realism
This layer is very important because it often “glues” the asset together, creating textural areas of common value and design language. Even though the effect might be subtle with a creature such as this dragon, dirt textures might be much more pronounced with hard surfaces.
TIPS
1. Make the displacement first and use a gray shader to judge displacement details and SSS, so as not to be distracted by color details.
2. Think about how the different materials lie on top of each other in reality and try to recreate this digitally and non-destructively.
The lighting rig is rather simple. My main focus was to shape and outline the features of the dragon nicely. I opted for a slightly stronger rim light that accentuates the teeth and head plates, to give it a more cinematic look. The key light is placed at a slight angle from the front with a directional fall of light to create hard shadows. I then used an HDRI for fill light, which helps avoid completely black areas.
Lighting breakdown
TIPS
1. For a nicely balanced starting point, use a mid gray material with a roughness of 0.65.
2. Analyzing real life studio photography can give you a good idea of light placement and settings.
Houdini allows the user to have different ROP nodes which is very helpful to use different render settings on the fly. In this project, I created a preview ROP node which consisted in a lower resolution, no DOF, a smaller bucket size, as well as a coarser pixel variance. The final rendering ROP consisted in a high resolution, plus DOF, and a finer pixel variance.
TIPS
1. Small image resolution helps reduce the render time, but keep in mind that you will see less displacement details.
2. Pixel variance is the most important sampling tool, as it tells RenderMan where it should focus its rendering power.
Thankfully the render came out of RenderMan very nicely and it didn't need much fixing in compositing. I decided to use photoshop because I have known this tool for a long time and I’m pretty comfortable with it.
The background consists in a simple soft background gradient with adjusted light and shadow contrasts on the dragon. I also increased the brightness in a few areas and did some post-processing. After a very small touch of color grading … voila!
TIPS
1. Keep it simple … less is more.
2. Keep the original image to compare it with your changes.
3. Don't over sharpen your image, as it kills realism. Like saturation, this is an effect that people like to exaggerate to the detriment of their image, as a real lens is not as sharp as a computer generated image.
Final image for Sorindar, the Gray Rock Dragon
This project is available with a Attribution-NonCommercial 4.0 International License. This allows you to share and redistribute for non-commercial purposes, as long as you credit the original authors.
