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Madeliefste Oh

Checkerboard distortion.. about phong reflection

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Hmm. Strange things going on with the uploader creasing. My object has 32 segments. yours has 16. If I use the 32 segment one, the uploader creasing works, but if I use a 16 segment version, the artefact is still there, as you found. For the 16 segment object, we should expect just 32 extra vertices, but, with the default 75 degree crease angle, we get 80 extra. I can't work out where they are from. If you increase the angle, the vertex count reduces at a couple of critical angles, but not as far as the expected number. The edge split works for both the 32 and the the 16 segment objects. It's preferable to the crease angle because you can apply it to just one of the rim edges (using marked sharp, not angle), so that is less increase in the vertex count.

If the artefact depends on the order of presentation of the facets to the rendering engine, then I guess there's no obvious way that the crease or the edge split should change that order. Neither is there any reason they should have the same effect. So perhaps it's not surprising that there are some cases where they don't work. Still, I think I would always prefer doing the edge split in Blender, because that gives you more accurate control. It also gave me the expected increases in vertex counts where I looked at them. I can't guarantee that it will always work though because I don't know exactly why having the edge split changes the order of facets for the renderer.

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Just wanted to add my experience and testing as my model was a bit more complex than the ones folks were using for testing.


I had a very tall and elegant champagne flute. Think "feminine" :D.  I had already solved the phong thing in the past (she thought anyway) with the two different materials. And that does work well sometimes but not always. I tried the edge split and it worked with ONE glass but not the very delicate tall one.

In the end I had to use all three tricks AND experiment with the edge split degree in order to get all the phongs to disappear. I suspect that the number and angles and such will change depending on the model so there seems to be no tried and true answer -- at least that was my experience.

But it also seems like if you REALLY want to get rid of those nasty triangles you can with some persistance. So if ONE method doesn't solve the problem try adding the next and the next.

I personally had NO success when I tried to use the same material. I am using Cycles render and 2.75.


That's all I got.


EDIT:  Well it took most of the day but I did end up with some nice glasses. The important thing that I found out was that while I had one perfect SINGLE glass, when I duplicated (applied rotation location and scale and mapped each glass of the group individually) -- the slightest bit of phong came up again down near the very bottom of the stem. Now you REALLY had to look but it was there.


Since I prefer fancier glasses I made the stems another material and didn't make that part transparent. I imagine that if I wanted to keep trying new settings that I could have eventually got it to upload without the microscopic triangles :D.  The top edge has gold trim.

.7 land impact for five, less for the set of three with good LOD holding at 2 (I use 4 myself). Happy with that.

And it is QUITTING TIME!!!


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