3d mask

[leoviale]

Hi, I'm trying create some sort of 3d mask for a rotating model, like i post below, and i can't find a way to do it. I need to create some object that i can use as a mask to occlude the solids that r getting inside overriding with it when the model rotates. I don't know if i need to use some material to do it or if there are ways to do that. Here i leave some examples that may help u see what i'm talking about. (the red solid would be the mask)

 

 

This is the model and the solid that I'm trying to use as a mask so it crop the other solids that r getting inside it. Below i leave u some examples that i get when i render the scene with Matte/Shadow material, and what another one edited erasing the solids that the "solid mask" should occlude.

 

This result is if i use the solid with some matte/shadow material. It doesn't render the solids, but it doesn't render the bottom solids either.

 

 

And this is the result I'm looking for, but don't know how to accomplish it

 

Edited July 16, 2008 by leoviale

[Claudio Branch]

The shape of the object you want to occlude resembles a Max primitive Tube. Have you considered just using a Tube and animating the slice parameter to achieve the occlusion?

[Peter M. Gruhn]

Create your selecting volume.

Manually select the objects involved.

Add modifier Vol Select.

Change settings to Object Mesh and pick the selecting volume mesh previously created.

Change settings to Faces.

Add modifier Delete Mesh.

Animate model. Because of the selecting the animating got boggy for me. But it worked.

[leoviale]

The shape of the object you want to occlude resembles a Max primitive Tube. Have you considered just using a Tube and animating the slice parameter to achieve the occlusion?

 

Yes, that's exactly what i used in the image i used before, but with the remaining objects i can't make them to "slice" or just start to disappear when r clipping the solid I'm trying to use as a mask.

[Dave Buchhofer]

best bet is to either follow Pete's attempt or to go the way of the ProBooleans route.. it should work fine if your part is modeled as a solid (no interpenetrations)

[leoviale]

Create your selecting volume.

Manually select the objects involved.

Add modifier Vol Select.

Change settings to Object Mesh and pick the selecting volume mesh previously created.

Change settings to Faces.

Add modifier Delete Mesh.

Animate model. Because of the selecting the animating got boggy for me. But it worked.

 

Well, this works almost perfect, it cuts the model in a very nice way, occluding faces as they touch the solid mask. I will keep looking up, but this method is a good way to solve my problem. Thanks allot!.

[leoviale]

best bet is to either follow Pete's attempt or to go the way of the ProBooleans route.. it should work fine if your part is modeled as a solid (no interpenetrations)

 

Never tried Pro Booleans. If u could explain how to use it so i can use the solid as a mask, i will appreciate. Thanks anyway.

[Peter M. Gruhn]

Just tried a quickie and the boolean worked well. I keep having them stop working well when the project becomes production level so I keep forgetting about them. The solid face on the cut is nicer than you'd get w/ the mesh select - delete method (Though depending on the mesh, maybe a Cap Holes would help that?).

[Dave Buchhofer]

yea it really depends on how you model the part as to whether booleans will work all the way through for an animated boolean. you can't really cheat corners/welding/snaps very much and still have things work

 

to try it out Leonardi, go to Compound Objects in the create panel. try it out on a copy of your geometry, as there are a few odd things and its possible to get stuck with something thats difficult to turn back into a regular editable poly/mesh.

 

when it works, its awesome.

[Peter M. Gruhn]

Right, now that I'm awake...

 

Prepare main object.

Prepare cutting object. Assign material to object for automatic visible cut surfaces.

Select main object.

Create Geometry

Compound Object

ProBoolean

Operation: Subtraction

Start Picking

pick the cutting object. Apply Operand Material for automatic visible cut surfaces.

 

Modify tab.

Expand ProBoolean (click on +)

Operands

Near bottom is a panel that lists the operands. Select the main object.

Animate it.

 

If I've describe correctly and you've followed correctly, the model should spin but the hole should stay fixed in space.

 

I made a more complex test model and it g o t r e a l s l o w. So rather than hold my finger on the mouse and try to target the correct angle of rotation, I am (even as I type this) trying this : Just rotate the thing and let go the mouse. Wait for it to calculate. Open the Track View. Find the rotation. Type my "360" in to that.

 

... Seems to have worked.

[Peter M. Gruhn]

OK, now it's working with two objects that were animated before the boolean. Experiment.

 

What isn't working is that the boolean is only recalculating DURING RENDERING for the first few frames.

 

I'm continually amazed by people who get professional production work out of this thing.

[leoviale]

Well, it works some times, some others i get a 3dmax error, i guess it's because the model have lots of polys. Anyway, it works the 2 ways, the probooleans way looks nicer, but takes some time to do it and it crashes if the model is too big. Well, I'm very pleased with both results anyway. Thanks to all of u guys, u saved me.

[nelpiper]

sorrys to get a little late to your question. I'm not sure about your question but since you alrady got the answer here is something that maybe can be of some use for you. If It is what I'm thinking I'd use a wireframecolor element (in my case vraywireframecolor). What this does is it takes every poly in your model and give it a different color at render time. so, when you're done rendering, u also got a mask of all the polys in your scene. You can take that to a post-prod program (like After Effects) and select precisely what u want and mask it, use blend modes, etc. I hope it helps. Good luck.

[mdviz]

Have you tried using volume select modifier on the mesh and then applied a mask material to that selection. It does leave open faces if you can live with that but is very simple and a lot more stable then a boolean operation.

 

Here I used a second volume select to give the illusion of the 'red edge' cutaway

[leoviale]

Well, it works just like using delete mesh modifier as I can see.