3D Triangle Terrain Generation problems

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#1

Hi guys, I’m currently working on a script that reconstructs obj objects using wedges. I’ve managed to get the main part of the script working where I draw the triangles using the obj data but have run into a frustrating problem. Since the wedges are 3 dimensional, a gap occurs where the different triangles connect.

example of gaps

b97b4ada1fce3cdfe35f1bb1b1b077ef
b97b4ada1fce3cdfe35f1bb1b1b077ef1287×741 90.5 KB

I’ve tried to inset the triangles down their local x axis but in every triangle, 1 of the two wedges has its local axes flipped and I can’t figure out how to determine which of the two wedges has had its axes flipped.

example of differing axes

05839f37af2a773a4a2271036aa00065
05839f37af2a773a4a2271036aa000651348×705 205 KB

Where the smooth surfaces represent the wedge facing outwards and the inlets representing the ones facing inwards.

If anyone could atleast point me in the right direction I’d be very grateful :smiley:

obj stuff.rbxl (41.9 KB)

#2

It’s most likely because you’re hitting the minimum part size.

image
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image

And you’ve lost float precision accuracy at this point. It doesn’t seem likely you can get around these exceptionally tiny gaps because you cannot get part sizes to go below 0.05.

Otherwise, your parts do have intersection points at the middle - which they should - if they could be smaller there would be no gap.

image

#3

I believe the problem occurs at all sizes. Also, not trying to scale up or down the wedges to meet but instead trying to move them down their local z axis (x in the case of wedges) by half of the thickness of the wedge so that the upper most edges meet.

#4

You can artificially solve these gaps

image

By adjusting your triangle to make up for them

	local w1FacesUp = right:Dot(Vector3.new(0,1,0)) > 0;
	local w2FacesUp = -right:Dot(Vector3.new(0,1,0)) > 0;
	local w1 = wedge:Clone();
	w1.Size = Vector3.new(0, height, math.abs(ab:Dot(back)));
	w1.CFrame = CFrame.fromMatrix((a + b)/2, right, up, back) * CFrame.new(-0.025 * (w1FacesUp and 1 or -1),0,0)
	w1.Parent = parent;
	w1.LeftSurface = "Inlet"
	w1.Name = "w1"

	local w2 = wedge:Clone();
	w2.Size = Vector3.new(0, height, math.abs(ac:Dot(back)));
	w2.CFrame = CFrame.fromMatrix((a + c)/2, -right, up, -back) * CFrame.new(-0.025 * (w2FacesUp and 1 or -1),0,0)
	w2.Parent = parent;
	w2.Name = "w2"
	w2.LeftSurface = "Inlet"
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#5

Thanks so much omG :smiley:

Would you mind if you could explain your solution a bit more, because I’ve been stumped on this for a few hours now and can’t believe its that simple… ;_;

#6

When you create a matrix and - in the case of wedges - the X axis is what we’re concerned about, the right variable (the X axis of the matrix rotation) is what faces up or down.

So, we must determine if we should adjust the wedge by 0.025 (half of 0.05) by subtracting or adding it.

The dot product returns a percentage (0-1 or negative 0-1) based on how parallel a vector is to the argument.

So 0,1,0 and 0,0,0 it would return “0”. 0,1,0 and 0,1,0 would return “1”

0,1,0 and 0,-1,0 would return “-1” and anything in between would be some float value.

In short, I use the dot product to determine if right is facing towards 0,1,0 or more towards 0,-1,0.

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