2 minutes of promising sculpting with a bad wakeup
I tried to create a 5 point star. To make life easy i started with a cylinder with 10 x-faces, then i created the star with some simple scalings and got a precise result at the end. But the baked sculpty was a true mess. Here is the 2 minutes video
blip.tv/file/get/Machinimatrix-howItGetsAMess476.wmv
Is this intended behaviour ? I later started a secnd try where i used 16 x-faces, then in top view combined and rearranged vertices until i got a 10 faces cylinder, then i sculpted the star again similar to how it is shown in the video above. But now after bake the result is as acurate as expected (even in SL it looks great)...
I have a vague idea what happens in the video, but i am still surprised since i expected the result to be of same precision in both cases. Is there a good explanation for the behaviour ?
Thanks for any answer,cheers, Gaia
Ratio problem
I'm not sure why you are modelling it that way, collapsing faces like that is generally a bad idea from a texturing point of view. But that aside, you start with 10 x 6 x 2 which gives a 128 x 64 map. This is the organic ratio where LODs are 46 x 22, 23 x 11, 12 x 5 and 9 x 4 - this means that "Clean LODs" doesn't work on this size as there are no power of two LODs for it to align to.
Using 10 x 4 x 2 for a map size of 128 x 32 should give better results. The Test GUI display of the LODs is worth watching to see what the final sculptie map LODs will be. Here they would be 64 x 16, 32 x 8, 16 x 4, 9 x 4 - ideal for a LOD resistant model. After adding the sculpt mesh, delete two edge loops on Y leaving just the middle one. You now have the perfect mesh and sculpt map for doing this shape with full texturing and 3 levels of LOD resistance.
Why i did it that way...
Oh, don't worry, i am aware that this is not "the best way to model", see below why i did it like this). I primarily want to understand why under certain circumstances the bake result is so different from the expected result. But for LOD see below, there is an issue with that !
So is the following true ?
1.) primstar only generates sculptmaps where width/height are always power of 2 values.
2.) If x-face AND y-face count are power of 2 values, the sculptmap will be precise (derivations only due to the sculpt-grid resolution)
3.) For all other values of x and y the final sculpt vertex locations are recalculated on a best fit basis (how exactly?) This is directly coupled to the "Clean LOD" alignment problem.
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Regarding the LOD counter: Something is different between the Test-GUI and the "old" GUI. Are you aware of that ? I only realised that, after i tried to lookup the LOD numbers you gave above... So in the old gui it tells me, that <10X, 6Y, 2Subdivs> results in 10 X-faces on LOD1 which sounds like the best i can have for my star. But in the Test GUI it is different.
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A last question is about texturing: Your model results in a slightly unprecise sculpty but it can be texturised. When i do it my way, i can create an absolute precise Sculpty but with horrible texturing properties. (Texturing it results in heavy texture jumps, i know that)
Now what if i wanted to have an absolute precise sculpty AND i wanted to texturise each plane surface of the star ? The point is, that my star only needs 20 faces. I could try it with small sculptmaps, but then i suffer from the "small sculptmap precision bug". So i must use a 1024 faces star. The only way i can think of to get 20 absolutely precise faces is like i did it in the video. Is there any better way to reach the goal without texture jumping effects ?
Precise sculpties
Second Life only supports power of two sculpt maps, so it makes sense that is what Primstar generates. For other values, eg 5 X, 6 Y.. It doubles up faces to make it the next nearest power of two. So on 5 X you really get a 8 X, 8 Y map with 3 double sized X faces and two double sized Y faces. With Clean LODs, the doubling is also done on the UV map, with it off the UV map is evenly spaced.
With geometric shapes, there's certain angles you have to stick to if you want precision and full texturing. For example, 45 degrees is fine as it's a 1 x 1 slope. 2 x 1, 3 x 1, 3 x 2 all give nice angles to use. I think if you work out all the angles available from the 0,0 point to the other points on a 4 x 4 grid, you end up with all the different angles that will work - 0 x 1, 0 x 2, 0 x 3, 0 x 4 all give the same 90 degree angle for example. 1 x 2 and 2 x 4 are the same etc.. The distance each line takes to go from exact point to exact point shows how many pixel colour steps are needed for that angle. So 1 x 3 needs 1 step in red and 3 in green (for an angle on X, Y). If face size falls below this or is not at one of these angles, you'll get the jaggies that the quick star I did shows.
Note: Most sculpties aren't going to have equal directions, while this can be forced with "Keep Scale", it's generally best to keep straight lines aligned with the axis (90 degrees in the above example) as other angles will vary depending on the overall size of the mesh.
Old LOD display
Forgot to mention, that the old sculpt mesh LOD display is the incorrect one. The Test GUI one is correct. It's one of the little bugs in the old sculpt mesh, it shows an LOD based on the number of modelling faces rather than the sculpt map faces. With hindsight, the old add sculpt mesh GUI was probably too buggy to merge into Primstar, but at the time I thought we'd just clean up the bugs rather than rewriting it.
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