Does this lecture imply backfaces are invalid in ALL game engines?

They say in this introduction that when you import a model into a game engine, the back-faces are culled, or told not to be drawn.

This is a huge shame, because backfaces sound like an invaluable feature for games, and i’ve always dreamed of having them!

Is there really no way to render the backfaces in any game engine?

I understand the performance implications of using backfaces irresponsibly, but it seems foolish to simply disallow them without a toggle-able setting for the game asset, such as bShouldDrawBackfaces.

As far as I am aware, they will never show in games by default which is why people can see through a solid object to the other side if they end up with their camera inside said object.

What is your intention to have double-sided faces for models? Interior of buildings? Vegetation?

Usually, when you create let’s say a wall unit, you don’t simply make one plane and say it is done. You would most likely create a thin cube to place around like actual wall pieces. So you’ll have your two sides to see like that.

If you are trying to do plant life or something, there is an option to have your planes/faces double-sided. So you should be able to toggle the setting, but I’d have to look into it to double-check how to do it.

Let me know, and I’ll respond back with a more accurate answer if someone else doesn’t get to it first.

Hope that helps~

Double-sided faces you say? Where would this option be, and/or how exactly would this mechanism work? By literally creating two faces for you or? some other special functionality?

I do realize you could simply add in the faces yourself, as I imagine is a common practice, but for general purpose it would be nice not to have your control limited by a non-configurable mechanism of the game engine.

Doing a simple experiment myself while following the lecture I flipped the surface normals of the wedge model

^Although doing a uniform scale presented some dimensional troubles; possibly more solvable with the dimension properties.

That should do what you want, but I think you should only use it on a few things vs everything. It will cost a lot more in resources to have it all over the place. I think I read using the extra geometry vs using double-sided is more resource friendly, also.

So apply a texture or something to your model, and then test it out and see what happens. Maybe put it into a game engine like Unity or Unreal to see. Use a Cube with one or two missing faces so you can easily see inside of it.

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Double sided normals - very cool. I wonder how this works however, as you’d think it wouldn’t be any more expensive as rendering the surface twice.

I’m going to follow along with the lectures for now but I’ll try this out later. Thanks for the tip.

I wasn’t planning on using this feature immediately but like, for instance, simply having large scale low poly models can actually be a good bit of fun in a game, especially with nice materials to fill the void, So simply allowing backfaces to be drawn could allow you to easily make some cool geometry without worrying about what faces are rendered where - also just a cleaner effect then having everything look invisible from inside or opposite sides of models, in a situation for a model where you think it might be needed later on.

A little detail on how this property works would be nice if you know anything more of it or wouldn’t mind typing.

Btw, xD , bit of a side-problem, but any idea why I dont get the Mesh Display properties like in this lecture?

(blender on left, lecture video on right)
^I cant edit any Mesh Display properties such as displaying the face normal directions.

This was already a problem before I started this thread.

I’ll respond back to your previous post when I can, but for your newest post, you need to be in Edit Mode to see that Mesh Display in your panel. Make sure you select Faces there and increase the Size to see it easier.

In the screenshot I posted I have a face selected and you can also see I am in edit mode O: :open_mouth:

I suspected it to be a version problem at first but then it started to get more fishy.

^ All faces selected and no Mesh Display section.

Isn’t that your mesh display there circled? That’s what I see in your screenshot.

Below the circle, click on an Icon for Normals. And increase the size. First is Vertex, Second is Edge, Third icon is Faces.

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What the - sorcery!

You know what’s wierd is I was extruding stuff then out of total random I saw those dots appear on my faces(hotkey maybe?). I was looking all over for that window in edit mode before though. In my first screenshot you can see I am in edit mode with… actually it is cut off. Hmm I dunno but I was looking all over for this earlier trying to replicate any settings he might of had - thanks for pointing this out.

There is still however a chance there’s a bug or exception, unless theres a hotkey I just hit now.

For your previous post about practical use for double sided normals, think about it this way:

First one is just 2 planes, are you going underneath it or above it? Are you approaching it from the side? Above or underneath won’t look bad, but viewing it from the side will most likely look horrible as it is only a slim plane and might not look visible at some angles. So you could potentially be running into something because you can’t see it.

Second one is a more proper way to model something, imo. It gives the 3D design it should have. You can give a generic texture or map it to have something more fancy.

Third one is a mix of the first and second. It might look ok from above or below, but a side view again will just make it too odd.

Fourth one would be more proper design of the third.


Then it will come to where you are putting these things. If you are covering something, let’s say making a motionless rock that’s a dome-shape without a bottom, you’ll never see it from underneath. So no need to make extra faces for a bottom.

If you are designing an interior or exterior of a building in separate load maps, they can be planes with just one side for texture.

Worrying about seeing through objects will be more or less an issue of placement / level design. And more importantly, collision meshes (which you will learn about later) will restrict both character movement and camera movement. It will depend on your settings when designing whatever it is you would be making.

Plants are something you will see later in the course. They usually will contain multiple planes put together with double-sided images to appear more lush and life-like. That’s a more practical use for double-sided normals. That’s IF you make your plants like that. They can be 3D models, of course.


In the end, it will come down to what you want to do. The only thing you are required to do is test everything for issues. Lighting might become an issue; clipping might be an issue; resource usage might be an issue.

Your vision is the most important thing, but it still needs to work and appeal to enough people if you are trying to sell a product.

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Hmm well from a collison standpoint wouldn’t it normally block you anyway? Or perhaps this isnt true- which would explain jumping up out of models from underneath them, due to the one sided collision forcing you upwards - xD.

I am not super concerned about the side view - most people are oblivious to how anything in a game works, or the valid mechanics that is there - they do not get to see such things in the sheltered scenarios us ******* designers put them in x|).

From a level design standpoint, this is indeed mostly the issue I am concerned with. As a creative level designer, not having a complete model can be very offputting - trying to find ways to utilize a half-rendered model with no sole side. Ever thought of making a bridge of trees strung together by their roots rotated 90 degrees on their side? You would need rendered geometry for the roots or else it would be very difficult to string them together.

So perhaps it is the distraught over this with designing levels in the past that spawns a desire to have these included.

But all in all while you make good points, I am not going to do something that doesn’t make any sense unless I find it to be fun anyway. Having the control only makes things more bearable. A control that which I have, and no dictator can tell me to do otherwise xD. That is the joy of finally being able to get a grasp on these powerful industry tools without any terrible spoon-fed environment we get subjected to in the potential wise - an awful uninspired creativity-void atmosphere we live in today completely unappreciative of the tools given to us gone to total waste. A waste even more so maybe to sit here talking about it, instead of gradually learning what I have missed on all these years; learned to be able to fufill the things I craved as possible in my head - things even as simple sometimes as large objects with viewable surface materials on both sides of its geometry faces!

(though preferably it would be nice to specify which faces can be seen on both sides- though this is maybe asking too much , haha.)

The collision mesh would encompass the whole object regardless of what side is approached. I’m not sure about the jumping through models … it might be that something calculates your body to be in one position when it is actually in another. Then it places you in the “predicted” spot, or maybe sends you flying with some sort of velocity lol.

What I meant was that it would be worse to be blocked by something you couldn’t see because it is too thin. But I am sure with what you are thinking, you could have the sides, even though thin, be curved or bent to be better to see / view.


The more you fiddle around and test with varying models, you’ll see what you like and what works. Then you can show us your stuff here :grin:

I think if you want to specify which faces are double-sided, make the whole object as you see fit first. Then in Edit Mode select all the faces you either want or don’t want to be double sided and press P to Separate by selected. Then parent the two meshes together with CTRL+P while in Object Mode. Then you can toggle either one to be double-sided or not.

I’m pretty sure that should work out how you want, but it might get more annoying depending on the complexity of the object.

Hmm interesting little workaround; I’m not even sure how too apply the double side filter though because he hasn’t gone over anything in the properties panel yet- and consequently it hasn’t worked for me yet.

Ive seen far worse collision problems in games then an easily identifiable blockade that can be seen by moving or jumping lol; but this would not be practical placement of said object anyway.

  • What I meant in that description is, in unreal engine for example; I noticed I could glitch through objects by walking underneath missing collision, but when I did this with landscapes - I was completly blocked. (However, when i controlled a physics object with UPhysicsHandle or whatever it was, I could move the object around through the bottom of the terrain just fine, so maybe it had something to do with the way pawn movement was controlled.)

I’ll post some work if I feel the need but easy there don’t jinx my progress ha.

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