Displacement help please.

[jamacdia]

Hello,

 

sorry im new to rendering, and especially forum etiquette, but i have a quick question, please. Every time i try to use displacement. It corrupts the geometry. I have attached an image. and this is what it always does.

 

some general notes.

The big displacemnt area is actually composed of 700mmx2000mm panels.

The panels are just planes.

Sketchup.

hmmm.. ive tried millions of render setting, makes no difference.

bump map works fine. But i can never get displacement to work.

 

thank you

 

alan[ATTACH=CONFIG]40952[/ATTACH]

[Brodie Geers]

Which render engine are you using? Typically, for displacement a surface will need to be subdivided for best results. For what you're doing I'd say something like .25m x .25m (you want your subdivisions to be square or as close to square as you can get).

 

I'm primarily a SU user and su isn't the easiest program to use for subdivision but there are ways to do it. I can share if that is your issue.

 

-Brodie

[jamacdia]

hi, right sorry i complete forgot to mention its vray. ok so maybe my panels are too big right now at .7x2m grid. I'll try sub-dividing it and letting you know how it goes. thanks for the reply

[Brodie Geers]

I'm a vray noob so I'm not familiar with the displacement settings. In Maxwell, there's also a parameter you can set within the material itself that determines how finely the mesh will be further subdivided at render time. So it's sort of a balance between manually subdividing the mesh and adjusting the materials parameter. The more you manually subdivide, the faster the render time generally. However, I'm not sure if vray works the same way.

 

-brodie

[jamacdia]

yeah that parameter does exist. and ive played with that, but it makes no difference still the messed up triangulation of faces. I just dont get why bump maps work fine but displacements mess up.

 

thanks

 

alan

[Brodie Geers]

That is odd. It's hard to tell from such a lowres image what exactly is going on. Could you post something a bit larger and maybe a straight sketchup image as well to see what the geometry looks like. and perhaps a screenshot of your material settings for the vray experts out there

 

-brodie

[jamacdia]

Thank you again for taking the effort to read these posts Brodie, I really appreciate it, even if theres no readily available solution.

 

So i have attached a basic render, a S.U. view, and a material setting scr.sh. As far as i can tell general settings dont change anything like Irradiance map etc.. etc..

 

So its clear that areas where the panels are "clipped" get distorted the most, but even straight rectangular panels get distorted, just less. Another thing i have noticed is the further away, the worse it appears. Also every render is different, sometimes panels over here, sometimes over there, etc..

 

cheers, alan

 

 

[ATTACH=CONFIG]41019[/ATTACH][ATTACH=CONFIG]41017[/ATTACH][ATTACH=CONFIG]41018[/ATTACH]

[Brodie Geers]

What are the purplish colored panels in the SU view? Those seem to be distorting the most.

 

Part of your distortion is likely coming from the fact that your panels are fairly large and rectangular. As I mentioned before, making them smaller and more square will at least help some. You might use something like Soap Skin & Bubble which can work quite well and give you perfect squares and allows you to choose the density. Or you could use the regular contours from scratch tool (make a plane, adjust density, rotate it into place, soften coplaner edges, intersect with model, cut away parts you don't need). What tends to happen is if your panels are too large the displacement doesn't have enough triangles to work with and makes these very exaggerated unpredictable changes.

 

Another tip is to use Soften Edges (I'm basing this on my Maxwell Render knowledge but I'll bet Vray works the same). You're getting some breaking at the corners. To avoid that set the Smoothing angle to something greater than 90 degrees (or just manually smooth the edges that need to be smoothed, or add a bevel at the edges and set the angle greater than 45 degrees...so long as the edge is smoothed your joints should connect).

 

Also, if you wanted to test further, I'd recommend turning off all the properties for that material other than displacement and zooming in on some of those problem areas. it's still not quite clear what's going on there.

 

-brodie

[Tommy L]

Take it from an experienced vray user, this is not a suitable use for displacement. Model it. Vray is a super fast raytracer and will gobble up as much geometry as you can throw at it.

[Brodie Geers]

For the record I would agree with Tom. Those ridges would be quite easy to model and would speed up your render time quite a lot.

 

That said, there will come some situations where displacement is better, and it's not a bad idea to work the kinks out sooner than later.

 

-Brodie