RENDERMAN WATER SHADER HOW TO

But very few materials in real life is truly that uniform as our material, even one colored things has variations in them. So far our example have produced a single colored material that respond to light roughly like plastic.

RENDERMAN WATER SHADER HOW TO

How to create surface shaders that correctly layer structures of different illumination models using the Kubelka-Munk model.

Then we extend our basic constant shader by using the plastic illumination model. In the example above we begin with making a copy of the surface normal and use the viewing angle to ensure the normal oints towards the camera.

Surface illumination_example( float Ka=1, Kd=0.8, Ks=0.5, roughness=0.1 )Ĭi = Os * PlasticBRDF(Nf, Cs, Ka, Kd, Ks, roughness) The name of the models is just descriptive and the 'plastic' illumination model can be used to render many non-plastic materials that just share the same characteristics. The most common model is some form of BRDF (Bidirectional Reflection Distribution Function), like 'plastic' or 'shiny metal'. And to make life a little bit easier there are a whole lot of illumination models available to choose from that can be reused in your shaders. This light repsonse is usually refered to as illumination model. it has to respond to light just like that material. So to make your shder look like plastic, metal, mud, etc. For example, a simple painted surface respond to light by reflecting a part of the lights spectrum (a red painted surface reflect the red chunk of the spectrum) while a shiny object reflect nearly all light. How materials respond to light that hit it is actually very important for their appearance. Which makes it pretty dull in the long run. So far the examples above have just been rendered flat, it didn't matter if there was any light present in the scene, and if there was it didn't affect the material. Note: This page a work in progress! The following examples will use header files not yet checked into CVS or currently shipped with K-3D. K-3D also come with a set of convenient shading language header files. The tag pair is to help separate your data from the other data that may be in the log.Īn example of using such data can be seen here. If you have a string var debug you can set it to 'y' in k3d when you want data output into engine.log. You can use output to engine.log to help debug your shader. One very good reason to avoid having to rerun k3d-sl2xml is that it will overwrite your customisations of the. And this way you can keep the test_shader we created above around as a playground for shader development.Īnother approach is to add all the instance variables you may need at the start, that way you do not need to keep running k3d-sl2xml. It may seem counterproductive to run sl2xml another time, but this is just a workaround since you may not always know exactly what instance variables you want or need. However, while developing a shader you can just declare them as local variables and set their values at the top of the shader, changing them to instance variables when the shader is finished and running sl2xml again. Just note that you can't add any instance variables to the above shader without first running k3d-sl2xml and restarting K-3D for them to turn up as properties in the Object Properties panel. Just edit the test_shader.sl file in your favourite text editor and saving your changes, then hit render in K-3D and it will compile the shader and render the preview. Then create some kind of geometry, maybe a sphere or a Newell primitive, and apply the material on it.Īt last we're ready to start write our shader code. Then fire up K-3D, select the MaterialShader object and choose our new test_shader to be used. Geometry of Shading Surface Normal (*) test_shader.sl.slmeta

How the surface position P is changing per unit time, as described by motion blur in the scene. The amount of time covered by this shading sample. The following table lists the set of global variables that can be used by Surface shaders.ĭirection of a ray stricking a surface point Jump to: navigation, search Global Variables

Renderman water shader