Hair simulation in Blender can be pretty diverse, but what’s the best way to create an old, worn-out look using a particle system? 3D Artist contributor Gleb Alexandrov talks you through the process in this exclusive tutorial.
The basic mesh can be either created from scratch or modified from another available mesh. For the sake of the content-sharing principles of the open-source community, let’s download a burlap bear model from www.blendswap.com/blends/view/759. This site is dedicated to Blender content sharing under permissive licenses. Open it in Blender and check what needs to be added into our main scene. Press F1 to add and select any necessary objects and use Proportional Editing (Connected mode) to alter the shape of the model. If you want to rotate body parts around a Pivot Point, set the 3D cursor to the desired location, then press the full stop on the keyboard or select the 3D cursor in the Pivot Point menu.
Let’s go through the stages of the hair simulation. First, we’ll need to create a draft particle system and test the basic shape and properties of the hair. The next step is combing it. We’ll then turn to Child particles, up the render resolution, set the Hair Render mode to Curve and then continue working on the details. After that we’ll use particle textures to make our teddy bear look old. So, start by adding the particle system to the mesh. Set the Number Of Particles to 13,000 and Hair Length to 0.132 (this value obviously depends on the scale of the model). Set Emit From Faces and tick the Even Distribution checkbox to spread the particles over the surface of the model.
Switch viewport to the Particle Edit mode, select the Comb brush and start styling. The brush strokes largely depend on the desired look for the hair. One thing to keep in mind is gravity – under its own weight, the hair will likely stick to the shape of the underlying model in some places. Also, you may want to force the hair to follow the curvature of the model – in the case of our bear, the strokes will form circular patterns. The hair will almost inevitably stick from beneath the surface in some places. It can be removed with the Cut brush. Using the inverse of the Cut brush, the Add brush, hair can be added to cover any bald spots.
Once the basic shape is established, we can set a higher resolution – and then immediately regret it, because what seemed to be a decent-quality fur will suddenly look terribly low-res. This means that we need to add Child particles to push the density up and also play with the Cycles Hair Rendering settings to add resolution to individual hair strands. So, set Children to 30 (Render) and switch mode to Interpolated, as we want the Child particles to retain the shape and direction of the parent particle. Tweak the Clump parameter to imitate the plush. Set the Kink to Curl, the Frequency to 2 and lower the Amplitude to 0.075. This will add twist to the hair and break up the repetition. The last setting to take care of is Roughness, so set Uniform Roughness to 0.1 and Random to 0.2. This parameter controls how chaotic the hair will appear.
The bald spots on the model are controlled by the particle texture – Clouds type, Improved Perlin basis. More precisely, the Density parameter and also the Length are affected by it. Set the Noise mode to Hard, bump the Contrast to something like 3.2 and Brightness to 1.7 to eliminate very gradual transitions between noise values. Tweak the Offset values and Size until you strike an aesthetically pleasing ratio between the bald spots and the long hair. After that, go to Edit mode, select all vertices and assign the Weight of 1.0, then switch to Weight Paint mode and paint some areas with Zero Weight to cut the hair. To see the effect, in the Particle Settings assign an appropriate Vertex group to Density and Length.
Let’s talk a bit about the underlying fabric material. Create two placeholder materials and name them descriptively to make the process that much simpler. In the Edit mode, select the parts that will hold the second material (the nose, the feet and the paws) and assign it. This will be the light fabric; so a Velvet shader, tileable image texture and the Normal map plugged in. The dark fabric will be the same with exception of an RGB Curve node, which controls the Brightness of the texture. The Hair material will be a mix between the Diffuse, Glossy and Translucent shaders. The Fresnel node controls the Mix Factor between Diffuse and Glossy, and the Translucent shader is simply added on top of it with a Mix Factor of 0.074. A Procedural Noise texture (Magic) is passed through the Color Mix node, and then goes into Diffuse Color Input.
This tutorial was first published in issue 69 of 3D Artist. Missed the issue? You can buy back issues quickly and easily from www.imagineshop.co.uk!
Our thanks go to Gleb for producing this tutorial.