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I have some prims that I need to drive through a Clip SOP. Each prim has got its own clipping plane origin and direction, previously computed and stored in prim vector attributes, eg v@clipOrigin and v@clipDirection I would like to connect these attribute values to the inputs of a Clip SOP: Origin & Direction parameters but cannot figure out how to do it. I tried (just showing the Origin.x parameter of the Clip here, but the y/z and the Direction.x/y/z would be analogous: @clipOrigin.x no error, but wrong result (alway zero) v@clipOrigin.x error: unable to evaluate expression - extra tokens detected in expression ch("../nodeJustAboveClip/clipOrigin/x") error (bad parameter reference) hou.ch("../nodeJustAboveClip/clipOrigin/x") error (unknown function in expression) also tried with a spare parameter I realize the clipOrigin is not a parameter on my nodeJustAboveClip SOP, but rather an attribute on its prim output. So 3-5 are likely just plain wrong. Just in case Clip assumes it is running over points rather than prims, I also inserted a Attribute Promote SOP to copy the prim v@clipOrigin to each point. With version 1 above, the result is the same - no error but always zero. If you know how to do this, thank you in advance ! This is in Houdini 16.5 Indie -------- SOLVED: I was using the wrong syntax in the parameter expressions. You can pick up prim or detail attributes in SOP (not just Clip SOP) parameters like this: prim(surface_node, prim_num, attrib_name, attrib_index) detail(surface_node, attrib_name, attrib_index) details(surface_node, attribute) point(surface_node, point_number, attribute, index) Note these are VEX expression functions used in parameter expression one-liners, not regular VEX functions used in wrangles. The signatures of the functions are slightly different.
Hi everyone! I'm currently working on a fairly "illuminated" scene, where I use loads of dim instanced point lights. Normal lights provide the option of setting an attenuation radius, which usually speeds up rendertime a lot, but the "light template" does not provide that option. As shaders I use the asadlight and rayshadow. Asadlight has something similar, which is an attenuation ramp that gets multiplied with the attenuation, so you can set it to black after a certain distance. I know this should visually have the same effect, but is it as efficient as the radius option in the normal point light? Is there any other way to "clip" light? The reason I'm asking about this is because I set the attenuation radius to black after a certain distance. I set up a render and it takes ages, despite the fact, that its only in range of about 4 lights. Once I deactivate the other lights, the render goes super fast. Any advice, experience, wisdom or other info is much appreciated! Thanks a lot Sustaxata