how to make a clipper similar to this

[6ril]

Hey,

 

I have a pretty simple scene (rooms made of polygonal walls (extruded curves and boxes)), and I need to expose the interior by "cutting" portions of the walls.

I tried with the cookie node, but it generate many many unwanted polys.

The clip node is too limited (clips from a plane only, and does not reconstruct the holes it create).

 

This clipping would need to be driven by a custom object/volume, and will be animated (to reveal the interior).

 

I guess it's all doable in houdini, but since I'm a beginner... I'd love to have your input on this.

 

latest version of Vray renderer is doing exactly that :

 

https://youtu.be/0XB5nAxQnzs?t=3m

 

[konstantin magnus]

i would stay with the cookie SOP. a few triangles wont hurt as long as you shade them well.

 

p.s.: if anyone comes up with a shader thats using object space instead of UVs I´d be very interested in seeing that!

 

 

 

 

cake.hipnc

[mestela]

Other options are vdb booleans, which will give you clean geo but get a little heavy if you have to convert all your surfaces to VDB SDFs, or you could try eetu's render time booleans:

 

https://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=31575&highlight=

[6ril]

Thanks guys... looking into it.

 

Matt, I'll try to learn about vdb and then try that out, as my geo is mainly boxes (simple rooms). Thanks also for the render time boolean info, I tried it, with a simple hollow box, and the inner faces aren't rendered... I guess I need to look more into it, as I can't even find where the trick is done in the hip file provided by eetu.

 

 

Konstantin, as I mentioned, the cookie sop is just too crazy. of course in some cases it can just do the trick nicely (like in your hip exemple), but for my case (hollow boxes) ("shell" object) it's just very buggy.

And when I said: "I tried with the cookie node, but it generate many many unwanted polys."

I don't mean it add poly but the topology is correct, I mean there's extra polygons at unwanted places, in your cake exemple it would mean that some poly of the noisy sphere would be visible outside of the cake.

 

I'll make a exemple file + render.

 

 

Thanks anyway.

[6ril]

ok,

here is an exemple of what I'm constantly encountering with the cookie SOP :

Pic and Hip

 

As you can see, there's a switch to compare the result of cutting a Box or a Box-made-with-polyextrude.

 

I've read that the cookie node is 10 years old and hasn't been retouched since... So is there any hope with the current state of it, to get usable results with cutting "modelled" objects ?

 

cookie-bug.hipnc

[konstantin magnus]

thanks for providing an actual file. in the example it would suffice to activate "output back" in extrude sop but maybe you left that out for demonstration purposes. may i ask what keeps you from modeling solids?

Edited February 19, 2016 by konstantin magnus

[6ril]

Stupid me !

 

The cookie SOP may have some weakness (as I've read in many forum threads), but those weaknesses aren't what caused my troubles !! 

 

You just saved me, Konstantin.

 

Thank you thank you !

 

Totally missed that uncheck "outputback".. And I knew about it!!! Stupid me...

 

Thanks again !

 

 

PROBLEM SOLVED !