Mantra

In Houdini you can use the so-called VEX Builder to create VEX code. Houdini's VEX language is loosely based on the C language but takes pieces from C++ as well as the RenderMan shading language. Inside Houdini's VEX Builder you can write VEX code with visual programming. You simply create nodes and link them together. The VEX code is automatically created, compiled, and executed.

In figure 3 you see the constant shader in Houdini. On the right side there is a Viewer Pane which shows you the result of the surface shader applied to a sphere. You can select several shapes to test your shader or create a whole scene with other shapes. In the latter case you have to attach the shader explicitly to the geometry. You can select several backgrounds¹⁷ which is quite useful in this case to see the transparency. You have to check the button to the right of the Background button to turn on the alpha display.

Figure 3: The VEX Builder