ZBRUSH SKIN EFFECTS
This image, King Of The Streets, is a personal project that was born from a meme that I found that said ‘Sit back. Relax’. I decided to transform it into a full-of-attitude small creature to send a positive message about the power of attitude, with a badass frog that might be tiny but rules the forest!
Every project starts from some research but do not get lost, you have to take decisions and I tell you this because it usually gets me trapped. Since this species has approximately 15-30 colour variations, I needed to explore a lot, Substance Painter was key for quick test workflow. After some exploring I chose this poisonous strawberry dart frog that kind of looks like Deadpool. I accentuated the anatomy and added some cool gang style props to get a more powerful character. I wanted to make it look like a rock star portrait so I played with the pose with a very direct look to the spectator and with dramatic lighting.
This tutorial will focus on the creation of the skin of this frog from start to finish. So it will guide you along all processes: sculpting the details, creating all maps and rendering the final piece.
This process also applies to any other software.
Break down the areas First of all, it is very important to differentiate each area and simplify them by breaking down into simplified structures to understand the complex details. On the belly area there are circular form-like cells. For this I used any irregular circle alpha with the Standard brush. You can easily make it in Photoshop deforming and blurring a circle with the Standard brush. For the cell wrinkles, connect the circular bumps (cells) on the belly following a continuous path with the Dam_standard brush in Zsub mode. Imagine a fishing net over all these bumps or water waves around rocks.
Add details I like to start defining the wrinkle by drawing with the Dam_standard brush and then to get the volume of the fold formed by the skin, I use the Standard brush with a bigger stroke.
I sculpted wrinkles for the lower eyelid by following the orbital eye movement. Some larger wrinkles appear behind the knee due to the flexing of the leg. Make sure these wrinkles vanish and smooth out when coming to the front side because this is where the skin is most tensed. Follow the same process for the arms. In this layer I also added some wrinkles around the lip and very small wrinkles everywhere around to add a more skin-like feeling.
Add imperfection The rough skin of the back has a more irregular surface so generate a general noise using the Standard brush with a big draw size set on spray mode and default 07 and 08 alphas. After, I try to use different alphas, bigger and smaller and then apply a general Smoothpeaks brush, this generates a more skin-like effect. I
do this process twice to get a very irregular surface and afterwards I do a final pass of very subtle details. Add some warts here and there, mostly around the rougher skin. Just use an irregular circular shape as the alpha, sparingly, around the skin with different sizes and intensities again with the Standard brush.
Work on the back Skin on the back is thicker and suffers a lot of compression and extension so deeper wrinkles form like an accordion. Remember wrinkles always go in the transversal direction to the movement. Finally, I always add a layer for the asymmetry.
Nature rarely stays symmetrical so it would look unreal if we don’t add some natural differences and it is a good opportunity to accentuate the expression of our hero character. I found it interesting to raise the smile a bit to get a cooler and more humanised gesture.
Bake maps To bake the displacement map I use Zbrush Multi Map Exporter. You need to set your low subdiv level from where you will apply this map later on in the shader. For the resolution I highly recommend 8192 so you get the maximum resolution. Set mid to 0 and 32-bit EXR. For 3ds Max it is important to activate Flipv, otherwise you will get the map upside down and a headache. For the rest of the maps I use the straightforward tool from Substance Painter’s Texture set settings/bake mesh maps, ideally set as 8k maps. It is important to export the curvature/cavity map. Another way to get this map is from Zbrush, by masking by cavity and filling with black colour. Finally, export the resulting texture from the Polypaint feature in Zbrush.
Create diffuse map First of all, I separated the belly and feet from the rest with a mask. For the back, just create a fill layer in red and add another layer named dots pattern with a generator, with 3D simple noise with the Position map as input. Basically, you can control the amount of dots with the scale control.
There is always some need to fix so I manually paint to correct any bad-looking areas. Finally, I add a 3D Worley noise on top for another layer of extra smaller dots on screen mode set at 25. Tip: you can activate/deactivate the mask layer by pressing Shift on the mask.
Finish working on diffuse map It is very important to be clean, so I made two folders: Belly and Back. The belly has a base layer filled in black and another layer with the curvature/cavity map used as a mask in normal mode in 10% of intensity, this enhances the hard work we did sculpting all the details in Zbrush. I will later use it also to mask Reflection roughness. Finally, I add finishing touches in Photoshop, adding a skin layer in soft light mode and painting manually the extra detail on the feet making them look like rock style gloves.
Shade The V-ray alsurface material is a great and easy-to-use shader for skin. Always take scale into account when rendering with SSS shaders. In this case the frog is 18cm high. This is not its real size, but this is okay for helping to control the SSS effect. You can always balance the effect with the scale factor. Next, plug in the diffuse map, normal bump and finally add the curvature map into the roughness and sss1 colour texture. Don’t forget to increase the SSS mix, otherwise you won’t get the SSS effect. Tip: for contrasting maps, the curves of the output mode in each map are really useful. The V-ray displacement modifier has a better control than the displacement map. Deactivate any filter blur on the map that is set as a default option. Plug a Vrayhdri map with the 32-bit EXR displacement map you got from Zbrush. The Texmap min should be -1 and 1 but you can play with values a bit.
Render I recommend to start simple, placing lights with no materials and move progressively step by step to displacement, bumps map, SSS shaders and the more time-consuming stuff. The recent V-ray interactive rendering is handy for playing with light intensities and positions. The scene is composed of three lights and a HDR light to provide interesting reflections. The main light is a big top area light. A back area light illuminates the right of the frog with high intensity, giving a lot of contrast on the back and highlighting the sculpt. A rim area light enhances the silhouette and makes our character look more interesting, and pop out of the background.
Finally, I add finishing touches in Photoshop, adding a skin layer in soft light mode