I wanted to write something down briefly. You can call it a tutorial or a how-to, an insight into my work or a working instruction that I can give to the next 3D contributor at the game 
. ;-)
I like to show you how to build windows in buildings with Blender 3.1. (Download for free) And when you think about, you learn more stuff, than just windows. Get creative! Without much talking:
The plan: windows in a wall. Including window frame and window cross.
The first picture shows the result, but also directly the procedure:
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I have outlined the edges of the resulting glass in the picture. Do you see the "error"? What is slightly "reflected" there is the edge of the pane. Because: the pane is exactly on the frame. And not a single millimeter in the frame. Somit sagt mir der Renderer "Hey, ich habe hier eine Glaskante, die mache ich Dir mal hübsch. Was aber am Ende zu Quatsch führt. Worse still later in the game: So there are now two surfaces, yes, on top of each other, as exact as can be. Nevertheless, through this slit, under unfavorable conditions, the shadow cast could show a narrow slit of light. This not only looks not very funny, but also has a really weird effect. This can be prevented by pushing the objects slightly into each other - even if it is only a fraction of a millimeter. Already the wall is slightly in the frame and also the window in it - without "gap" in between. |
Step by Step:
1: Create a wall (20 centimeters thick on the X axis).
2: Make a cylinder (brown, 30 centimeters thick on the X axis) protrude through the wall and shape it as desired.
3: Give the wall a Boolean modifier, select the brown cylinder as a stamp and apply it directly.
4: Duplicate the brown cylinder and scale it down a bit on the Y and Z axis. Scale up X, give gray/different material for clarity - as in the picture, this gray block must pierce the brown block on both sides.
5: Give the brown cylinder a Boolean modifier. Take the gray cylinder as stamp object and apply it directly as well.
Now everything is cut. Now a few things need to be scaled properly. On the one hand:
6: Scale the gray cylinder on the X axis to 2 centimeters.
7: Now swap the gray to a glass material and it looks done.
However, as mentioned above, it is not. We still need to put the wall and the window sheath into the frame. To do this:
8: Take a frontal view. (Do you know the number function on your Num-Pad?).
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Let's start with the windows at the bottom left. There is already a window cross integrated here - but don't let that irritate you. The windows below are created exactly like the windows above. |
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On the left window you can see how we need it. The right window is not yet properly interlocked. Can you see the difference? On the left, you can clearly see how the intersecting edges of the wall, the window border and the window inside it do NOT overlap, but are pushed into each other. |
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The window frame at the bottom left, marked in orange. You can see it well: from the outside the wall protrudes into the frame, from the inside the glass pane protrudes into the frame. This is how it should be in the end. You can also see that the pivot point is in the middle of the frame - this is important for the following scaling. If the pivot point is anywhere, now center it on the mass or surface of your window frame. |
9: Select the window frame and scale it up on the Z and Y axis. (Tip: normalize the scale to 1 beforehand; then you can set precise steps instead of making pi times eye). In our example, a scale of 1.01 is sufficient.
As soon as you have scaled up the frame a bit, what happens? Correct, the pane becomes too small. (You could have scaled only the outer vertices, then the inner diameter would have remained the same. But since the glass has to be scaled as well, the way to do it with less clicks is to scale the complete object right away). |
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I wanted to highlight that the slice is now too small at (normalized) Scale 1 - see at the highlighting. |
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Scale 1.02 to Y and Z push the edges into the frame. 1.01 would be too little - because then the edges would sit exactly on the frame as at the beginning, but not in it. |
It's basically done now. But this is where optimization for computer games begins. If an object (our wall, windowsill, window) is visible on the player's screen, it must be calculated. If we disregard special techniques, the complete object with all its surfaces is always rendered, even if only a small part of it is visible.
This circumstance is very important for the modeling and compilation of game worlds and interacts with other factors. For example, sometimes you might want to save individual objects together as one object, or keep the objects in the game individually. Everything would have its reasons, benefits, associated opportunities, pros and cons.
In our case, however, one thing is clear: the surfaces of the wall or pane that now protrude into the window border can be deleted. Simply to reduce the areas that need to be rendered. This is one technique (of many) to consider when aiming for the best possible performance.
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I moved my perspective slightly, went into edit mode, activated the surface selection, selected all surfaces that are completely in the frame and now: Delete surfaces (X on your keyboard). We now repeat the same for the faces of the wall, which have now disappeared in the window frame. Grid view, select surfaces, delete: |
For best performance there are many other factors, not only the number of surfaces. The number and complexity of objects or their meshes is also a factor, glass is generally not a performance booster because you have to render a pixel multiple times in a bad case when you view thru. And sometimes not just once, but 2, 3, 4, or five times. But before we write down a complete course "what you should consider when designing 3D for your game", I'll end the tutorial here.
Bonus task to think about:
You've basically already learned how to add a window cross here. A square cylinder, thicker than the window itself. Of course, again without surface at the beginning and end of the rods, since these areas are hidden in other components.
Why single cylinders, instead of struts modeled out of the frame? Could have been done, but since all surfaces have to be triangulated cleanly for export, the object would have ended up with more surfaces instead of me just "sticking" a cylinder in there. Try it out, test, compare and think about what you are doing. That's how you develop! And someday you will make your own computer game?
Any interest in another How-To? Was that interesting for you? Would you have thought that it would work like that?
Any questions? Please post your questions, ideas and comments below or contact me via Discord, username powerpaul! I'm looking forward to!
Greetings from Paraguay!
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