Making a Witch Cauldron in Blender and ZBrush

Alex García talked about the production of the Halloween-themed project Spooky Witch's Cauldron: modeling and texturing stages, UVs, boiling liquid, and rendering in Eevee.

Introduction

My name is Alex García and I live in Málaga, a city in the south of Spain.

I am currently creating good pieces for my portfolio so that I could have an internship opportunity or an entry-level position. I have not had the opportunity to participate in any projects or work at any company yet.

I started my studies at odin3d.com through the mentorship programs. The teachers of this online school are seasoned professionals who worked in the video games industry on titles like Metroid or Spacelords. I also bought someUdemy courses on ZBrush, Substance Painter and Blender. At first, I wanted to be a programmer but over time I realized that what I really loved was the art branch.

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Spooky Witch's Cauldron: Start of the Project

I started this scene in the middle of August simultaneously with another project that I will publish soon. I wanted to create some Halloween themed scenes because that's one of my favorite times of the year.

I created my own concept – I'm not an expert in concept art but I have some fundamentals skills in drawing. I created some silhouettes with the references that I found and then drew over them and discarded the ideas I didn't like. I painted the cauldron in greyscale, then looked for a color palette adding cooler and warmer tones to avoid making the model look boring in the same color tone. I used this palette later in Substance Painter, too.

Reference

I used a lot of references to make this personal design. I searched for references that caught my attention even if they were not exactly what I was looking for. You need to look at the colors or maybe some small details that draw your attention. You also need to remember that you should leave some areas without detail so that the eye can rest. The idea is not to add all the things that caught your eye in the references but to filter them until only the ones you like the most remain.

I looked for some references of crows and human skulls, too. One of my best inspirations for making the candles and other additions was looking at references of the Santa Muerte (Holy Death) rituals in Mexico. They have a lot of cool candles + skulls combo references.

Modeling

I did the basic modeling in Blender, with the mirror modifier applied to the pieces.

Here's a tutorial of how I make the chains:

After basic modeling, I exported the base mesh model to ZBrush using the GoZ addon, which can instantly export meshes to ZBrush with a simple click. In ZBrush, I made organic props like the skulls and the liquid. I usually use Blender for making all the hard-surface pieces, then I export them to ZBrush and add some more details like cracks, damage, wear and tear, as well as trim the borders. I broke the symmetry of the model with accessories such as skulls, candles, and branches. I used some Orb brushes to give cracks to the skulls and the wood.

UVs

I always do the retopology and the unwrap in Blender. I imported a really decimated piece so I could build on top of it the low-resolution version. First, I created a simple Checker Material and gave it to all objects so I could keep track of the texel density and UVs distortions. Then, I placed the seams and unwrapped the model until it had no deformations in the Checker Texture. Once I went through all the meshes in the scene using the same process, I activated the Visualice Stretching tool in the UVs tab to check that everything is in order. Then, I select all the islands and use the button Average Islands scale, it normalizes the size. Finally, I made the islands of the non-visible areas smaller in the UVs to save space. An extra step that I like to take is packing everything using the UVPACKMASTER addon, it organizes your UV islands really well.

Texturing

When I have my retopology and UVs ready, it is time to do the baking and begin the texturing phase. My favorite program to do the bakes in is Marmoset Toolbag, it has really nice features, for example, you can correct the errors in the normal map projection in real-time with a brushstroke. It would be great if Substance Painter could implement this feature, too.

For the color ID map, I used ZBrush's plugin "Zcolor". Decimate your object and then use the plugin to make the color ID map easily.

For the textures, I used a low opacity base from SoMuchRoughnes for all the props as I wanted to give them a little stylized look. I then used my warm and cold color palette that I mentioned earlier. I like to apply it with the texture "Camo Woodland" and blur it to blend the tones. Then I added other layers for roughness, rust, dirt, and even a bit of dry green liquid on top of the rope and the central skull.

A quick tip for doing things like leaves is to import a plane and opaquely paint a silhouette. From there, I work on the edges and the leaf veins so that they have a little bit of height and are not so flat.

Liquid

For the liquid, I made a base with different spots in dark and light tones.

I also put some emissive spots with a bit of blur and a small radial height map for the effect of the waves. I used Eevee as the engine. There, I increased the subsurface scattering of the liquid so that it seemed viscous. For the shader of the liquid, I merged 3 node textures that give me radial waves, then I animated the value and fed this texture to a bump node. I also animated the candles with a simple Noise modifier in the Timeline Bar.

For the bubbles, I used a simple shader in which you can control the base and fresnel color. Also, I added emissive to the edge. The bubbles are animated metaballs; when scattered with a particle system they merge and give a cool effect.

Lighting

I used an HDRI that gave me the maximum shadow from the model. The Sun is the main light source in the scene and creates the shadows. I used 2 blue area lights to illuminate the back of the cauldron (to give a lot of volume to the model) and a third area light with a warm tone in front of the model as a fill light. I used 4 animated point lights to increase or decrease the intensity of the candle lights as needed. I also used two extra point lights to illuminate the liquid so that it looked like an emissive material. If you add fog to your scene, be aware of your lights because they can be revealed. In post-production, I added some animated particles to add a magic touch.