# Decimate modifier is reducing faces, even though the set angle is smaller than the Angle Limit set

The decimate planar reduces the number of faces depending on the angle. But there's a 110-degree, but at 52 degrees, the face is reduced. Why is the face decreasing when it's less than 110 degrees?

additional question. 180-129 = 51. So I see it flattened at 52 degrees. But I have one more question. Why is it decimated like the screen shot above? Shouldn't the 52nd degree be straightened out? Shouldn't it be straightened out like the red part?

It's less than 35 degrees, and it's getting decimate.

• It's unclear what you are trying to communicate here. Use the edit link to edit your question and communicate it clearly. Dec 3, 2020 at 15:20
• I'm sorry for my poor English. I've revised the article and I hope the questions are clear. Dec 3, 2020 at 15:29
• I don't understand the indicated 110° but decimate planar is to say "consider planar geometry that vary less than the indicated angle, and decimate it". Dec 3, 2020 at 16:05

A test case:

From left to right: 90° then 30°.

If we go above 30° in the modifier the 30° angle is decimated:

Now we have a 105° angle:

which means the angle variation is 75° (180 - 105°) following the edge (or face) variation.

So if the modifier angle goes above 75°:

... the edge collapse again.

That means the modifier is "cumulative": it will decimate all parts where the angle variation is below the given angle in the modifier.

• thank you. but i have one more question. i add the question. There are times when the decimate modifier ignores several angles, why is that? I thought the face would be decimated as if it were painted in red, but it spread out like the last screenshot on top. Dec 4, 2020 at 5:28
• 148+32 makes it toggle. When it decimates, that creates a new angle that itself makes toggle the other one. Dec 4, 2020 at 6:49
• 32 degrees is straight and 145 degrees bigger, so it's below 33 degrees. Thank you! For letting me know. Dec 4, 2020 at 7:12