[jnorion]

I am having a very odd problem with material rendering between Sketchup and Maxwell. I've created a piece of furniture sitting in a room, and am testing various lighting and material options (I'm fairly new to Maxwell). However, when I applied an MXM file with carpet material to the floor plane, the carpet appeared to change shape and overlapped the bottom of the dresser.

Here's what the geometry looks like in Sketchup:



And here's what it does when rendered with the carpet material:



The carpet material I used was from the resources library, here: http://resources.maxwellrender.com/sear ... v2=0&tipo= I didn't make any changes to the mxm settings.

If I render the scene with the default material from SU it appears normally, and if I use a different mxm carpet file (http://resources.maxwellrender.com/sear ... v2=0&tipo=) it also works normally.

Using Maxwell Suite 2.7.20, Sketchup Pro 8, plugin 2.6.10, on OSX 64-bit.

Can anyone explain what's going on with this, and how I can fix it? I would really like to use the original carpet file I selected. Thanks!

[JDHill]

Pretty sure the MXM you applied has displacement, and if so, it looks like you either need to use higher precision (called Subdivision in MXED) in the displacement, and/or more detail (more triangles) in the geometry to which it is applied.

[jnorion]

Seems I have a lot to learn about displacement. I checked the settings on that material and subdivision was set at 16. Not knowing how far to change it, I set it to 64, thinking that would be very high. The result was this:



Does this mean that I need to set subdivision much much higher? Looking at the example image in the Maxwell documentation (here) they show versions at 2.5, 12, and 32. While I know that my experience doesn't necessarily match theirs, it seems strange to me that I've doubled the max value they showed and am getting a less detailed result than the most basic.

I'm also wondering if this is an issue of geometry scale... i.e. Sketchup is exporting data measured with different units than Maxwell is reading, or something of that sort. But since I'm exporting directly from SU to the renderer (not going through Studio) I'm not sure where to check or change that.

[JDHill]

First, check the displacement height units -- you can specify height absolutely, in centimeters, or as a percentage of object size. Everything inside of Maxwell is in meters, but you don't need to worry about that, because the plugin takes care of making sure that any necessary scaling is done.

Then, regarding precision, pay special attention to the detail of the surface to which you apply the displacement material: there is an interplay between the Precision value you use, and the detail of the mesh. Reason being, texture pixels are being stretched across that mesh; if you have only two triangles but thousands of pixels, it takes a lot of computation to figure out what to do with a particular pixel. So the more triangles in the surface, the more detail you will get for a given displacement Precision value, and the faster the rendering will go, when using the On-The-Fly displacement type, or the more memory it will require, when using the Pretesselated type. Here's a screenshot showing the effect of increasing the number of triangles in the mesh:

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[jnorion]

I'm going to resurrect this after some months because I'm only just getting back to this problem and still haven't gotten it sorted. Everything in your last reply makes sense, except I can't figure out where to set the detail of the surface. As far as I can find, Sketchup doesn't offer the option to adjust detail on a flat plane, only on an organic shape mesh. How do I set this??

Thanks again!

[JDHill]

Correct, it doesn't have any kind of detail option -- you have to draw the actual faces you want, whether manually, using Draw > Sandbox, or using some 3rd-party plugin.

[jnorion]

Oooh, I get it. So the screenshot you posted above has one flat rectangle plane and one "Create from Scratch" terrain mesh that just hasn't been distorted at all? That makes much more sense!

[JDHill]

Yes, basically -- but I believe in that particular example, I just copied the plane on the right, and then drew a bunch of lines using midpoint snap.

[jnorion]

Tried last night with a sandbox mesh and it worked perfectly! Thanks for all the help.