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backface culling using mesh to create tight corridors and hallways


Vierge Fatale
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My idea is to create a hallway or corridor/small room and use the backface culling of a mesh object... --say a cube that is turned inside out so that only the inside surfaces are visible. 

Example:

backfaceculling.jpeg.8c18f85598439e308bd3feef9b248efb.jpeg

This is a full cube, but the outer surfaces of the cube are not rendered, allowing the viewer to see whats inside.  Another good example would be the Sims series where the walls are culled (or at least translucent) when they would otherwise block the avatar from the cameras point of view.

My question:  is this possible in SL?  I'm learning blender and would like to know how to essentially turn my cube inside out to try this (on blender).  I have searched and I cannot find anything that really explains this... it seems it would be something so simple but I'm not able to find anything. 

The goal here is to create a tight hallway that constrains movement of the avatar without obstructing their view.

 

 

Thanks

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Ran into my next problem:

While the backface culling of the mesh structure/corridor that I'm walking through allows me to see the path ahead clearly, the camera is still constrained by the mesh (ie. I can't keep it zoomed out, it wants to follow me inside very closely over my shoulder).

I have tried using no physics (have to do that to be able to walk inside of a mesh anyways) and using invisible prims for collision, but I get the same result.  Phantom mode doesn't constrain the camera, but also allows me to walk through the mesh itself.

What I'd like is for the user to be able to walk through the mesh corridor, constrained by its walls, but with the camera zoomed out... otherwise the backface culling is totally moot.

Any suggestions?

 

Thanks

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11 minutes ago, Vierge Fatale said:

Any suggestions?

In Preferences -> Advanced Check "Show Advanced Menu"

Then in the Advanced menu, select "Disable Camera Constraints".

Btw, what you did with the normals isn't strictly speaking backface culling, there are no backfaces to cull in Second Life. What you did was reverse the direction the mesh faces were facing.

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33 minutes ago, Vierge Fatale said:

Ran into my next problem:

the camera is still constrained by the mesh (ie. I can't keep it zoomed out, it wants to follow me inside very closely over my shoulder).

Yep, the SL official viewer doesn't have the capability to ignore the walls.

TPVs do, it's not disable camera constraints though. Whirly did a post yesterday on it here:

where she mentions "On Firestorm the option is "Allow the camera to move without constraints through prims". But again, SOL on the Lab's viewer and in TPVs you have to find and turn that option on.

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8 hours ago, ChinRey said:

Btw, what you did with the normals isn't strictly speaking backface culling, there are no backfaces to cull in Second Life. What you did was reverse the direction the mesh faces were facing.

Could you explain the difference?  The check box option for blender to render the mesh in the same manner as SL is even called "backface culling".

 

8 hours ago, Callum Meriman said:

Yep, the SL official viewer doesn't have the capability to ignore the walls.

TPVs do, it's not disable camera constraints though. Whirly did a post yesterday on it here:

where she mentions "On Firestorm the option is "Allow the camera to move without constraints through prims". But again, SOL on the Lab's viewer and in TPVs you have to find and turn that option on.

I was afraid of this, but I guess you can't have everything.  I would imagine that most people have the camera following pretty close by default anyways so I guess it's not that big of a deal.  At least now when you zoom out you will be able to see whats going on.  Not giving up, but I need to throw together more content to see how it will look.  My idea is like a space-station setting:

corridor.thumb.png.d09805b1861ebd3e03b654b3056f454f.png

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37 minutes ago, Vierge Fatale said:

Could you explain the difference?  The check box option for blender to render the mesh in the same manner as SL is even called "backface culling".

In Blender you can usually see both sides of a mesh surface. The "front face" is the one pointing in (roughly) the same direction as the normals, the backface is the one pointing in the opposite direction and it si usually rendered in a slightly darker shade. When you flip the normals, you essentially turn the surface inside out so the "front face" become the backface and vice versa, but they're still both there.

In Second Life and in Belnder with backface culling enabled, the backface is removed completely so you only see one side of the surface.

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5 minutes ago, ChinRey said:

In Blender you can usually see both sides of a mesh surface. The "front face" is the one pointing in (roughly) the same direction as the normals, the backface is the one pointing in the opposite direction and it si usually rendered in a slightly darker shade. When you flip the normals, you essentially turn the surface inside out so the "front face" become the backface and vice versa, but they're still both there.

In Second Life and in Belnder with backface culling enabled, the backface is removed completely so you only see one side of the surface.

Right.  Which is what I did, but you said "what you did isn't strictly backface culling".  What did you mean?  If blender says it's backface culling, and SL is culling the back face, and they both look the same when you enable the backface culling option in blender, how is it not backface culling?

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1 minute ago, Vierge Fatale said:

Right.  Which is what I did, but you said "what you did isn't strictly backface culling".  What did you mean?  If blender says it's backface culling, and SL is culling the back face, and they both look the same when you enable the backface culling option in blender, how is it not backface culling?

Oh, we may have a misunderstanding here. I was responding to this one:

14 hours ago, Vierge Fatale said:

I actually figured it out... it was simple: reverse the normals.

 

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11 hours ago, Vierge Fatale said:

Could you explain the difference?  The check box option for blender to render the mesh in the same manner as SL is even called "backface culling".

Some 3d modeling and rendering apps have a 'backface culling' option, to allow you to choose if 'backfaces' are rendered or not, with the uv mapping and shader applied to the 'frontface', that is what backface culling is, "dear 3d rendering app, do not paint and render the backside of the polygons'.

SL cannot be told to 'paint and render' the backface of poly's as far as I am aware, so there is no 'backface culling' option to 'turn off' a feature it doesn't have.

Simply inverting the direction of normals isn't 'backface' anything its just altered normals.

As for using 'inside out meshes' for tight spaces, yeah it's possible, check the marketplace for a full perm kit called 'building blocks 2.0' if i recall correctly, which has a selection of full and partial cubes both right side out and inside out. The pieces are pretty much free useage, and low land impact, you need an L shaped wall to stick outside the windows of a skybox, theres an inside out 2 sides of a cube item in the kit, ready made, just slap your cityscape textures on it and scale, or corridors, 4 sides of a cube inside out, each side a different face for floors walls and ceilings.
 

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