davpe

i looked into your file and this is gotcha everybody bums into at some point if you're assigning materials like you did, you have to indicate that there are materials embedded in packed prims (normally, mantra doesnt look into it to save resources - this can make a difference for large scenes). so all you have to do is to set Declare Materials option to Save All Materials. It's in Mantra ROP>Rendering>Render tab all the way at the bottom. anyways, more up to date way to handle materials on instances is Material stylesheet which i suggest you to explore. there are several pretty good tutorials covering this on sidefx website.

not sure, it works fine for me. might be the way you assign materials... hard to say. can you post a scene file?

there is no limitation in modeling, VOPs, animation or L-systems. really just DOP nodes aren't there.

Houdini Core doesn't include DOP nodes so you can't do any simulations. other than that there are no restrictions. Solver SOP is there too.

i think this is the community. i don't know any better dedicated to houdini. finding houdini lighters is harder than maya ones for sure as houdini up until recent years wasn't really focused on lighting tasks (and most lighters knowing houdini well enough have got a ton of work). but the situation is changing lately and people are starting to use houdini more as a general purpose 3d package so it should be easier to find all kinds or houdini artists in the future.

i'm afraid you can't use stamping like this. you can't stamp from different contexts (shader in your case). use print VOP to read and manipulate image file names stored in shader or you can use vex arrays to do that. here you go a suggestion how i'd handle it in it's very basic form: https://vfxbrain.wordpress.com/2018/06/14/using-arrays-with-vex/ look for an example with butterfly textures. cheers

well you can make your "beauty pass" whatever you want. you can make depth your "beauty pass" if you wish. in the example i posted, just the mask was the beauty pass because real "beauty pass" shaders were overriden in a style sheet and never evaluated in that particular render. it all depends how you design your materials. if you have some complex shading with aovs as a part of the same shader tree, then you have to execute the entire shader to get the aovs, but you get all that in one go. if you forgot about some passes before rendering your main pass, nothing stops you from building those additional shader bits and pieces aside in a separate shader, use style sheets to build overrides and render just that very quickly. then you can easily merge those new shaders with the original one so you don't have to keep rendering those little forgotten bits as a separate sequence for future versions. hope this explanation makes sense edit: maybe you will understand better if i say that you can't get just aovs without rendering the main pass, but you can make your main pass empty (or put anything else you want there with use of style sheets), but still get you aovs. so you don't ever have to waste time on rendering something you don't need.

yeah style sheets are really great for building passes and working with many objects/instances. not sure what do you mean by "switch off beauty pass"...

here you go the hip file refl_mask_pass.hiplc

you can use style sheets to make material overrides for that standalone pass. all objects visible for reflection mask will have white constant material and the receiving object will keep the "beauty" material but with everything except reflections disabled. lights would be off. for convenience you can merge those two rops and render them in sequence so you don't have to run them separately. this works best if you want to isolate ground reflections or so. not if objects are reflecting each other, obviously. if i have some time later i can post you an example file if you care. cheers.

yeah that loop and copy method won't work with arnold as it doesn't support packed primitives.you can still use the method but you won't get instances, only copies :/ mantra is so much better in this respect.

oh you mean that... well that's unfortunately not built into mantra by default. you would have to do some shader writing to get that. agree it'd come handy sometimes. i just render separate pass if i need that. not a huge hassle.

don't see how that topic is similar but masking works just fine.

any particular reason why you're using instance object? that's sort of old school approach to instancing that only makes sense if you use 3rd party renderer. randomizing things this way is quite limited. it's just instancing whatever is there in the source object. use loop and copy to points instead. take a look at this video

what if you plug your mask into a reflection color parameter? that should do the job, right?