Volume select only on already selected polygons?

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  12 December 2012
Volume select only on already selected polygons?

I am not sure if this is even possible. But here is what I want to do.

I have an object, and I want animate a hole in it. This is a rather simple process of course. I created an animated b/w map in After Effects, loaded the image sequence in the material editor in 3DSMax, but it in an opacity slot of some material and applied it to my object. And because I only wanted this animated opacity on a specific area of the object, I selected those polygons, gave them another material ID, applied a multisup object map to the object and used an UVW map modifier to place the animated texture correctly.

So no problems there.

But, I like to know if this is also possible using a volume select modifier.
If I apply a volume select modifier to my object, and set it to use a texture for the selection with a delete modifier on top of that, it applies it to the whole object, not to the polygons I have selected.

I guess this is normal behavior, and I am not sure of what I am trying to do is possible. But the reason I ask is that with the second method (using a vol. select) I can put a shell modifier on top to give the object some thickness. A texture with an opacity map doesn't give me that.

So any thought on this one would be welcome. Tx.
3D In Your Hands | 3D Visualisatie Bureau
http://www.3dinyourhands.nl (Yes, its dutch)
  12 December 2012
You must be doing something wrong in the Vol.Select, it works as expected.

*Create a Plane with 100x100 segments
*Add a Vol.Select
*Set it to Face mode
*Set it to Texture Map, pick a Checker map
RESULT: You get a checkered selection, 2 quarters selected and 2 not.
*Add a DeleteMesh modifier - the selected faces are deleted
*Add a Shell modifier - the rest is extruded.
*Open the Checker map in Material Editor, keyframe the U offset parameter from 0 to 1 over 100 frames and you get two animated holes moving over the object...

Even better, use a Gradient map set to white, white, black and Radial mode. Invert the face selection in the Vol.Select to select where the black is and you get a round hole!

Last edited by Bobo : 12 December 2012 at 07:58 AM.
  12 December 2012
I wonder if the OP is having a mapping issue.

At what phase does it fail? What parts succeed? Does the selection work but the delete fails? What settings do you have in the Vol. Select? IIRC it defaults to "object" and not "face" or "vert"...
  12 December 2012
Tx for the reply guys.

I guess I wasn't completely clear about what I want.
There is no problem with the vol. select modifier, as I said the results I have work as expected.

This is what happens now:
- I apply a vol. select to my object
- I set it to "texture map", pick an (animated) texture
- The vol. select selects faces from all over the object according to the b/w texture applied to it.
- Adding a delete and shell modifier do what they suppose to do.

What I am trying to do is the following:
- Select a specific portion of the object
- Apply a vol. select modifier.
- Do the rest of what I wrote above, but I want the vol. select to operate ONLY on the portion of the mesh that I have selected. And not on the whole mesh as it is doing now.

As I said before, I guess this is normal behavior of the modifier, and I am not sure if it is possible what I am trying to do. I can do it with just a texture applied to the selected polygons, but this doesn't give me any thickness on the model.
3D In Your Hands | 3D Visualisatie Bureau
http://www.3dinyourhands.nl (Yes, its dutch)
  12 December 2012
I tested this with my simple Plane setup and Radial Gradient and it worked:

*I added a manual selection above the Plane and before the Vol.Select using MeshSelect. I selected 1/4 of the faces.
*I changed the Vol.Select to Subtract Mode and disabled the Invert option I had before.
*So I had White background in the map and a Black hole in the middle. The result is that the white areas of the map REMOVE the existing selection coming up the stack, while the Black does not remove anything, and the faces I had selected in MeshSelect that happen to be under the black texels remain selected.

In the above image, the top mesh is the original plane with Vol.Select set to Replace selection and Invert checked so that white does NOT select, while black does. This produces a hole in the middle where the non-white pixels are.

The middle mesh is the Plane with the manual MeshSelect face selection.

The third mesh at the bottom shows the same Plane with the Vol.Select set to Subtract and Invert unchecked, thus producing selection only where the black hole does not subtract from the existing face selection. The rest of the mesh remains unselected and thus not affected by the DeleteMesh.

Last edited by Bobo : 12 December 2012 at 05:39 PM.
  12 December 2012
Tx bobo for your help.

I can reproduce your example, but it still isn't exactly what I am trying to do.

Using your example, what I like to do, is that the whole operation takes place on the selected part of the mesh. As with a texture, you can asign it to a specific part of the mesh where it would appear.

I included an image on this post:
Here I assigned a texture to demonstrate, but I like the white part to be just green here (so using the normal texture) and the hole to appear on the black spot of the texture.

Hope this clarifies some things.

Reproducing your example, however, it seems I have to create a lot of polygons on the object to make it appear smooth. If that is the case I might be better of using a texture with opacity map after all.

Sometimes... *sigh*
Attached Images
File Type: jpg SelectedPart-01.jpg (63.2 KB, 4 views)
3D In Your Hands | 3D Visualisatie Bureau
http://www.3dinyourhands.nl (Yes, its dutch)
  12 December 2012
Why don't you convert your bitmap to splines (e.g. trace the bitmap in another application to turn it to curves, or draw it in Adobe Illustrator or even in Max itself), then just use the ShapeMerge compound object in Cookie Cutter mode to create the effect you are after?

What does the REAL bitmap look like?
  12 December 2012
The real bitmap is an in AE animated b/w texture, growing from nothing to some sort of ink spot and than to a normal circle. I'am creating an animation where the camera zooms onto an object, and while zooming cuts away a part of that object (using the texture map) to reveal whats inside the object.

But I have done some tests the past few days, and at first I thought the best approach was to use some sort of cutaway of the mesh with a shell modifier to create some depth. But after doing some tests I think the best approach is to use the texture as an opacity map anyway. I though it wouldn't look good at a high rendered resolution (1080p), but it didn't look that bad after all. Also I have to take time into account, so I shouldn't spent more time on the project then needed.

I am still wondering though if something like what I asked is possible, so I will try your solution later on. Its interesting to see in what other way's such effects could be achieved.

Thanks for your help anyway. But terrible sorry for wasting your time on trying to give me a solution I am not going to use after all. At least, not for this project.
3D In Your Hands | 3D Visualisatie Bureau
http://www.3dinyourhands.nl (Yes, its dutch)
  12 December 2012
Don't worry, nobody's time is wasted when discussing these things. We are all learning in the process
  12 December 2012
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