VEX, VOP, SHOP, WTF?

[mark]

Vex is the Houdini shading language, which can be written in a text editor and requires compiling like renderman shader code. This gives you total control over your shaders but it's not simple stuff, even if you have done some programming before.

VEX Builder in Houdini is a visual way to create shaders. For example you create a Lighting Model VOP (Vex OPerator) which is set to Blinn, this is then connected to the output node to create your Blinn shader. VOP's are to shading as SOP's (Surface operator) like Subdivide are to modelling - they are steps in the process towards the final output.

SHOPs in Houdini are comparable to a Matlib in 3dsmax or the hypershade in Maya. It's a collection of shaders. They can't be modified directly but you can explore the underlying VEX network to make changes. You assign the SHOP to your objects to give them a surface shader in this example, but SHOPS are also used for lighting and shadow shaders amongst others.

To create the SHOP from VEX builder: operator menu -> create new SHOP. The shading network is ready to use as soon as you create a SHOP from it, no compilation is necessary by the user.

To assign different shaders to different parts of the one object, use the Shader SOPs when modelling and assign your SHOPs to them. you can have a complex model, with each piece assigned a different SHOP, all piped into a merge SOP which ties together the complete object.

<i>feel free to make corrections or elaborate on these points.</i>