This tutorial was written by the amazing Rainer Duda and appeared in issue 111 of 3D Artist. Subscribe today and never miss an issue!
In this tutorial we’ll take a closer look at the physical plausible material system of Clarisse with the integrated physical standard material, which is identical to Arnold’s standard shaders. As an example we will shade a bowl filled with raspberries; to make our work easier we’ll start by shading a single raspberry and apply the final material to a large amount of raspberries for the final shot. We’ll start by creating a nice diffuse colour and end up with a system that randomly shades the raspberries based on a colour gradient.
A combiner, one of Clarisse’s powerful tools, will help us create a single object out of a bunch of raspberries. By using a combiner we are able to call the vertex IDs and use them as an input for random colour application. An ambient occlusion node helps us to darken the areas of the raspberry where the small cells are merged together to add thickness and dirt to the borders. The same principle will be used to drive specular colour and roughness attributes for better-looking reflection behaviour. Furthermore we will investigate how we can add more detail and detail variations into the corresponding roughness layer for the first and second specular reflection layer to create a natural look. At this point we are starting to use heavily fractal noises to create interesting-looking patterns. An important thing to remember is that raspberries do not have a perfect shape, so you can achieve a lot more detail and realism by using a proper displacement material.
Last but by no means least we will need some detail under the hood – subsurface scattering. A raspberry is filled with water and therefore if the light source is emitting enough light, it will travel through the surface and be scattered below. Subsurface scattering enables us to add the final touches to the raspberry and with some distance changes, tuning the global scale and the addition of a lighter red SSS colour, we can get a tasty-looking raspberry. The last step covers the setup of major rendering attributes as well as some nice compositing features within Clarisse. We’ll learn how to create a final image with fake lens diffuse, a small halo effect and a self-made and artistically controllable vignette effect. Let’s get started!
Step 01 – Prepare your scene
Working on a material applied to the final geometry can be hugely time consuming. Usually when you want to create a material you start with a small piece, like a shader ball, but in this case we have a single berry. Enable the object called single_berry in the folder Main_Scene. Create a new physical standard material and name it M_Berry. Put the material in the same folder and create a new displacement object from the tool menu. Just call it Disp_Berry.
Step 02 – Add some deformations
To give the berry a more natural look just apply the newly created deformer object via drag and drop to the single berry. Increase the displacement height of the object by 5cm as the front value. To the left press the checker texture icon and in the new window create a fractal noise object and apply it. For the fractal noise set the projection to spherical in 3D space with Y as the up-axis. Make sure the projection scale fits the berry and remove the hook at Normalize. Use the colours and UV scale to create a decent-looking deformation pattern.
Step 03 – Set up colour information
At first, enable all of the lights in the project: one distant and one environment light. Select the M_Berry material and open the material editor. Let’s create an occlusion node and append it at the Diffuse Color slot. Use a dark red as the occlusion colour. This will be the colour for the connection bit between the individual small cells of the berry. The colour will be a lighter red, something like 0.42. Use a value around 2dm as the Radius and create a new group for the occluders. Call it berries and add the rule *Berry*, then under Inclusion Items select all alembic berries.
Step 04 – Work on the SSS
One characteristic of a berry is that it has a soft appearance paired with a bit of translucency and subsurface scattering. Select the M_Berry material and jump to the SSS section. Increase the Mix up to 100%. Use Empirical as the diffusion method and increase the overall density to 14. We’ll only stick with the first SSS layer, so increase Weight 1 to 100% and choose a light-red colour with a Distance of 30m. The Density Scale is a more global scale value for all layers; for fine-tuning take the Distance 1 value.
Step 05 – Add plausible reflections
For Specular 1 and 2 we take an occlusion node, just like with the diffuse colour. We leave the Color at one and Occlusion Color at zero. Under Geometry add the same geometry group as in the diffuse colour, called berries, but increase Radius up to 3dm or bigger, depending on your taste. This will guarantee that we don’t have any specular reflection where the berry cells are connected. Connect the occlusion node with the Spec Color 1 and 2.
Step 06 – Adjust roughness for realism
The reflection value isn’t enough in terms of details. We need to adjust the roughness with another fractal noise node. Set the projection scale to spherical in 3D space with Y as the up-axis. Also make sure that the projection scale fits the bounding box of the berry. Shrink the UV Scale value down to 0.005 for XYZ and remove the Normalize flag. Now take the colour values to create a noisy effect on the surface of the berry. Afterwards create a blur node, append it to the noise node with a Radius of 5cm and connect it to the Roughness of Spec 1 and 2.
Step 07 – Colour variation for all berries
Let’s disable the single berry and enable the table and the bowl. Right now the berries are simply single berries in the folder Berries4Bowl. Select all of them and combine. Unhide all single berries and make them unpickable. Move the combiner to the folder MainScene. To give every berry a unique colour, open the material editor, create a utility node and set the output to vertex ID. Connect it to a new gradient node. Set up the gradient with all the colours you’d like for the berries, plug it into a texture instance colour node and use this node as an input for Colour 1 at the occlusion node.
Step 08 – Choose the right perspective
The image also needs an effective camera perspective. Create a new camera and choose a perspective. Afterwards, make use of the depth of field functionality to add a bit more realism to your image. Select the camera, jump to depth of field, activate it and set F Stop to a really small value. Do not use the berries as a focus object but rather a Locater (Null) object in order to be more flexible with the visual output in the image view.
Step 09 – Set up the renderer
Under the Scene folder there is the PathTracer object, which enables us to change attributes regarding the rendering process. It is important that under the Rendering tab the PathTracer is set as the render engine. For the Anti Aliasing Filter it is the best to use Blackman-Harris with 3px filter size. To get a clean image we must increase the Shading Oversampling to a value of 50% or more, depending on the quality output and/or the underlying CPU power of the workstation. In the Material Sampling tab bump up the SSS Multiplier by a value of four.
Step 10 – Lens diffusion and halo effects
Clarisse enables us to make some nice visual enhancements to our render picture within the layer editor. The most common effect we see is lens diffusion followed by some small halo effects. Both can be faked with a simple trick. Jump to the layer editor and create a new reference layer based on the underlying 3D layer. Decrease its visibility to 0.1 and move to the tab called Filters. By pressing the add button insert a Gaussian blur filter and increase the filter size to 10px. You can repeat this step a second time with a filter size of 3px and a layer visibility of 0.25.
Step 11 – Dust, scratches and noise
Imagine you have taken an image with a DSLR camera. What you see after you zoom into your image-editing software is noise at a certain level of the zoom. To create some good-looking dust and noise select the base 3D layer and jump to the Filters tab. There is a specially designed noise filter which you can use. Set the amount to a value of 1%, use zero as the min value and for max stick to the default value of one. In addition make sure you hit the flag at Monochromatic for a good-looking image effect.
Step 12 – Final vignette effect
At first we must create a new colour layer in the layer editor. In the attributes scroll down and switch the colour from white to black, afterwards add a new filter called Add. Now we’ll go to the Add filter and add a new cellular noise node to it. Set Dot as the Pattern, decrease the Jitter to 0 for XYZ and set Frequency to 1 for XYZ. For the Border Mode select Smooth with a 50% Border Amount and 35% Border Size. Flip the colours so that the cell colour is white and border colour black. For the colour layer’s blending mode, select Multiply.