Simple translucent shader

Translucency is a phenomenon quite common in surrounding us world. It should not be mistaken with transparency. Transparent objects pass light - as glass, however translucent objects pass light only partially. In transparency phenomenon light rays' direction after passing transparent layer is unchanged, in translucency rays passing translucent layers are slightly bent.

SimpleTranslucentShader is created based on translucent and PBR diffuse mix model based rendering. This model is modelling translucency by scattering transmission rays upon surface intersection. This shader is suitable for mostly one-sided or double-sided thin geometries for which translucency is required, such as sheet paper or leaf material.

Firstly we need to configure logging, RendererContext and ExampleAssistant.

Then we load a scene.

Then, setup lights and scene background.

Then we can set up materials for our test objects. The scene consists of two leaves. One of leaves is assigned a PBR and a second SimpleTranslucentShader. Behind the leaves there is a point light located, enabling visualization of translucency phenomenon. Now, lets setup leaves. We will start with PBRShader leaf. Each material, as described in 12_materials tutorial, requires the following parameters to be fully defined:

• provider - asset and data source for material (e.g. texture loading interface). In this example we will use FileTextureProvider, which binds ours script with texture directory,
• procedure - pack of programs responsible for shading - for a first leaf we will use default one, for a second SimpleTranslucentShader,
• parameter_provider - parameters required by the procedure to work - these allow further customization, we will present with a second leaf using SimpleTranslucentShader,
• strategy and randomization_group - rules for randomization, not used in this demo script.

We will now define the parameters for SimpleTranslucentShader rendering. These are described in detail in the table below:

Finally, we can set up render chain, post process steps and visualization.

HINT: See 13_render_chain.py for more render chain configuration examples.

Then we can setup, print and render our scene.

Let's change values of some parameters of the shader to get better understanding how they influence render. We will start with base_color by decreasing value of Red channel and increasing Green channel. We will use generate_renders_with_setup wrapper, so we have less lines of code.

Now we will return to the previous values of the leaf color, however we will increase value of translucency roughness expecting a leaf to bend rays more causing a leaf behind to be more blured.

Let's decrease translucency_roughness value to get sharper leaf.

Now we will decrease translucency value what will cause leaf to pass less light.

Now we will increase translucency_roughness to again blur a leaf behind a bit.

In the final render let's add texture provider to the leaf with translucent shader.

Other parameters can be also modified in the SimpleTranslucentShader, however modifications presented in this tutorial should be a good starting point for the further experiments of this shader's capabilities.

The end.