Displacement and antialiasing problems

[dlparisi]

I'm trying to do a scene that is basically all white (i.e no bitmaps) but I am running into problems with displacement and antialiasing problems. Here's the rendered image and a few settings:


I'm trying to acheivce the different materials through a displacement map (for both the bricks and the vertical siding). As you can see it turns out a little weird. First, the weird displacement of the bricks is obviously related to the triangulation of the mesh but I don't know how to fix it. I know if I switch to 2D displacement it clears up but I can't do that because the bricks need to wrap around corners. Any suggestions? There was a thread a couple weeks back that suggested placing a meshsmooth modifier with a .99 smoothing value and operate on triangles but this didn't help. Anyone have any other ideas?

The second problem deals with what are the best setting for antialiasing the lines in the vertical siding (also done through a 2D displacement map). If I turn up the Max rate to like 4 and drop the threshold it clears it up but it takes forever. Similarly the times go up if I switch to Fixed or QMC. I have normals checked but don't really know what the spinner values next to it represent (doesn't seem to be mentioned in the help file)

BTW-The model is a linked dwg file. There's a direct light with Vray shadows, environment light, IMap/LC (medium/700).

Thanks, David

[studioDIM]

Re: Displacement and antialiasing problems

There was a thread a couple weeks back that suggested placing a meshsmooth modifier with a .99 smoothing value and operate on triangles but this didn't help. Anyone have any other ideas?

The second problem deals with what are the best setting for antialiasing the lines in the vertical siding (also done through a 2D displacement map). If I turn up the Max rate to like 4 and drop the threshold it clears it up but it takes forever. Similarly the times go up if I switch to Fixed or QMC. I have normals checked but don't really know what the spinner values next to it represent (doesn't seem to be mentioned in the help file)

I'm afraid you're right: i was the poster for that, and it did work for me on a curved spline. When i tried it on a straight one it didn't work at all.

As for the AA, i'd increase only the min sampling to something like 1 (so 1/2). It should take less than raising max as it won't have to step so many times for each pixel, but it's debatable, i guess.

As for the 3D versus 2D displacement, try the one that works best, and then you might split the mesh where needed (in the corners, i take it?)

Hope it helps...

Lele

[DaForce]

I would also try Adaptive QMC AA as well.. you will find the details better.

And if needs be bump it up to 2,5 to get even more detail.

[Morbid Angel]

daforce - based on my many tests qmc aa of 2/5 will not do any difference.

dlparisi, first off the dispalcement error looks like is caused by bad geometry. Look here

http://www.chaosgroup.com/forum/phpB...=116701#116701


As to antialiasing i recoment 0/3 of adaptive aa with object outline checked and also not use sharpening filter like mitchel, rather quadratic.
You may also need to lower your displ subdivisions. With edge length at 2.0 20 subdivisions will be good enough, not 512.

[DaForce]

really..oh.. i noticed some differences in some of my recent renders.
Ahh well

[studioDIM]

Dmitry is right on the displacement side, but i thought that you could do little editing on the mesh at all.

That's why i suggested splitting it after finding the right method (splitting it in autocad, of course).

If you can edit the model in max, though, it should be fairly quick to slice it in a regular pattern with the edit poly modifier, and then get rid of the traverse edges and remaining vertices (using backspace to delete them).

Sorry if i'm sounding obvious, i don't know how much of a max modeler you are

For AA, raising max samples with a threshold left intact wouldn't impact on your rendered output (if the threshold is missing detail, the antialiaser won't step up, no matter how high the max level).
In other words, raising min level asks the AAser to "dumbly" oversample all the pixels, hence resolving the detail that was lost beforehand.
While it might seems silly to do this (and it might well turn out to be, in some scene), it balances out with the fact that there are just two levels for the AAser to deal with.
Well, i'm sure it does work this way with Mr (1-2 is WAY faster than -1/2 with lower thresholds), i am not sure Chaos hasn't got a better AA algorithm in place.

On the other hand, if "object outline" is the key factor, then it should work also with the sampler at -1/2.
From some tests, though, it seems to make no difference whatsoever on the bricks outline, as they are pretty straight facing towards the camera (difference mode overlay in photoshop).

Also, while my test image with AA at 1/2 and no Obj outline rendered in 33 seconds, the one at 0/3 with Object outline took 46, and the difference between the two is VERY small in the grout areas.

Feel free to experiment yourself, though : )

good luck,
Lele

[dlparisi]

Thanks for everyone's help. I'm getting a little closer to what I want. Because of the bad triangluation on the geometry, I ended up using 2D displacement on the brick and just pushed the grout lines in rather than pushing the bricks out which kept my corners closed.

The best antialiasing setting for speed/quality seemed to be adaptive 0.3 with a .15 threshold and .1 for the normals. Checking "object outline" didn't seem to make any difference, though. Morbid: thanks for the new thread on proper geometry for displacement-I'm going to watch it closely.

I am curious about resolving the tesselation of the surface for better 3d displacement. I'm not much of a max modeler so I'll probably try to split things up in autocad as Lele suggests. I'll try slicing it in Max with the Edit Poly tool (is Edit Mesh OK? because the linked autocad model comes in as a mesh) too but I need to get a better handle on how to do that. As a quick first try though, I've applied the subdivide modifier which gets me what looks live evenly spaced polys. The render however still showed the edges of the polys. Why didn't this work?

Again, thanks for everyone's help.
David

[studioDIM]

You can either turn the mesh to a poly object (right mouse click on it, and choose "turn to poly"), or simply add an "edit poly" modifier to the stack.
Edit mesh isn't as good as the poly object for editing, as it lacks a few features.
I personally consider it a legacy object.
Nothing will change converting the "Mesh" to "Poly", though. You'll just have more control over it.

have fun poly editing!

Lele