How to achieve an oblique sectional view?

[TomA]

Hi,

 

Just wondering if it's possible to create an oblique sectional view of a model in 3d max, ideally without physically splicing / cutting the model in half or something similar.

 

I know you can create sectional views easily with camera clipping planes, but they always have to be more or less perpendicular to the camera view don't they?

 

See photo for the kind of view i'm after... (not my model/photo just one taken randomly from the net)

 

Ideas?

 

Cheers

 

P

 

http://i260.photobucket.com/albums/ii31/puttyface_101/O2/2611_0185_1_w.jpg

[BrianKitts]

what about grabbing the model that you want to cut, add a slice modifier onto it and set the cutting plane for rendering. Then when you're done just delete the modifier and all is still intact.

[Peter M. Gruhn]

before - camera with clipping plane looking pretty much straight on at bldg.

 

after - clone of camera, only changes are roll and perspective correction modifier with heavy abuse. The camera was not moved. "Problem solved" at the expense of distortion and not the nicest controls, but I think I win the "it can be done" prize. Note, that this picture had to be rendered vertical and rotated after the fact.

 

Clipping plane solution is good because advanced lighting solutions (it would appear) pay no attention to the fact that some geometry is "missing".

 

So I got to thinking and had an idea.

 

above - solution using a falloff map in Cutout. Distance from object. I used an omni light (casting no light) so that I could use it's attentuation gizmo to show me where I might want the slicing plane (NOT really a plane, is sphere. Bigger attenuation and further light, the more like a plane. You can see some curve here at... 2520 inches distant.) and a very handy readout of exactly how far that is from the object in question. Set the near and far distances in the falloff to the same thing. You can separate them (I suggest making near smaller for GI reasons) for a fuzzy edge, maybe multiply by some noise...

 

cam - same technique from boring unclipped camera

 

wire - same but material switched to Blend and falloff moved from Cutoff to Blend Mask. OK, I moved the camera a little to show the bldg better.

 

Back to advanced lighting. If the physical properties of the building "utterly transparent" then photons are just gonna go busting through. I figured this out as I saw the GI calcs go from "well, that's done" to "eight percent. eight percent. beuller. eight percent". So I made a big plane, gave it a number of segments this way, slapped a bend on it to match the curve of the omni's attenuation (I told you that would be useful). Slapped a matte gray on it the same shade as my base material and turned on cull backface. It's in there, huge thing, but we're looking through from the back and it's bouncing photons back in to the scene. How to treat it re: color may get more complicated as you start using real materials in your scene. It should make things brighter at the slice than they would be otherwise. W/o it things are clearly a bit darker. Consider making the material darker than "room average". Consider using a box gradient brighter on the edges where the walls and floors reflect directly back in and darker in the middle where the reflectors are more distant.

 

The overall overhead isn't THAT bad. Make one falloff map and supporting goo. Slap the falloff map in the Cutout slot of all your Arch/Design materials. You ARE using Arch/Design materials, aren't you? Don't know how to deal with your tree leaves that are allready cutting out. RGB Multiply. A little bit of extra work. Not too bad.

 

You could, of course, just slap a slice modifier on everything and call it a day. The bounceback plane helps here too, I'm finding.

 

OK, that's all I can think of for now.

[Peter M. Gruhn]

Slice modifier image for fair play's sake. By far the easiest one, I thought.

 

Heck, the only reason I went through all the other bother was because I went to Max, looked for the Slice and couldn't find it. I must have misread. Maybe it's something to do with the section compound object or... I thought I'd played with... nah, must be mis-remembering.

 

So I did all that material garbage. Then I try again. One box. Look, Slice modifier. Ah... first time I'd just done a select all and gotten lights and cameras to which you can't apply a slice. Geometry only. Select all. And there we go.

 

Oh yeah, if you end up doing the bounceback plane - shadows off. About a third of my lighting is outside the clip area so the narrow end of the scene got really dark. YOu can see it's still not perfect, but it's not bad. Probably less of an issue with more of the actual model shown.

[Crazy Homeless Guy]

This isn't necessarily a 3dmax solution, but it may serve as an idea for some.

 

...but if you are designing with Revit, you could position section cuts of the BIM model, and then save out FBX files while in a 3d view of the section cuts. The FBX file will be saved as a section model for import into 3dsMax, or whatever software.

 

This may be a feature in other BIM software also.

Edited January 26, 2009 by Crazy Homeless Guy

[Peter M. Gruhn]

> revit

 

Nice touch. Thanks for the info.

[TomA]

what about grabbing the model that you want to cut, add a slice modifier onto it and set the cutting plane for rendering. Then when you're done just delete the modifier and all is still intact.

 

Thanks guys, but the first suggestion worked a treat!

 

Cheers

 

P

[BrianKitts]

This may be a feature in other BIM software also.

 

Brilliant!.... never thought of doing that one. In Archicad you can draw any path for outlining the plan you want to generate for 3D, which allows you to do some great un-aligned section cuts.

 

Typically we marquee off sections of the BIM model to export for rendering, but I've always done in from the vantage point of only including what I need, I've never though of pulling sections that way for rendering and using it as an exclusion method.

 

nice tip travis.

[Winniman]

after - clone of camera, only changes are roll and perspective correction modifier with heavy abuse. The camera was not moved. "Problem solved" at the expense of distortion and not the nicest controls, but I think I win the "it can be done" prize. Note, that this picture had to be rendered vertical and rotated after the fact.

Hi,

May I ask how do I do this process?

Thanks,