Dear Houdini Guru's,

i have many lights in my scene and an heavy shader, to test the light, i would like to somehow replace the shaders to a “standard” one, so that i only can see were the light hits.

Is there a clever way to do that?

thank you very much!

• 1. Easy one: takes.
  
  2. Less easy one: script.
  
  3. The least convenient at first and most robust at last. Make python script: filter.py:
  
  import mantra
  def filterInstance():
  mantra.setproperty('object:surface', ‘opdefShop/v_plastic’)
  mantra.setproperty('overridedetail', ‘1’)
  
  and call mantra with it:

  mantra -P filter.py

  (you can place it in Mantra ROP on Main tab. It will replace any shader assigned in Houdini just before rendering.

another easy way to change shaders is to start using different rops and use the object parameters in each rop to describe your scene. you can make a new geometry object and then object merge all of your other objects into it. then merge all of them together and use a material sop and point to your simple shader. the material sop will override the shader path attrib where the parameter on the geometry object wont, so make sure to apply the material inside.

then make a different mantra rop and under objects, delete the * from renderable objects and select that new geometry object under force objects.

i highly recommend working like this. ive used takes before and they can quickly grow to be a nightmare. using different rops for everything is really intuitive and very powerful.

a good idea when doing this is to make one master rop, then right click on it and select make a reference copy. this essentially makes a new rop with channel references to every paramater on the master rop, so any time you want to change your sampling or any other setting in the render, it gets pushed down through the other rops.