Hi, can you help please with drape?

monks

Hello to all. I'm trying to drape an image over a terrain mesh. I did do it successfully but I can't repeat it! I even wrote down the things I did, but it still doesn't work.
I have a terrain mesh, over which I have a drape. I also have models placed on the terrain. I need to change the drape to another one.
Can anybody walk me through the process? I'm using Sketchup 7 at the moment.

Thanks in advance,
monks

Gaieus

Hi Monks,

There are two, different terms here. "Draping" means you drape geometry (usually 2D lines) onto a 3D terrain mesh.

"Projecting" an image is a different thing.

True however that the process is quite similar. Let's see the projection (since you are talking about an image).

I guess you already have the terrain. Hopefully its perimeter is a rectangle (if not, no worries - it is just a bit more tedious). Be sure to make this terrain a group and smooth its surface.
Now draw a rectangle (or any shape of your terrain's perimeter) and carefully align it above your terrain.
Import your image a texture and apply it onto this rectangle carefully scaling and positioning it to your liking.
Right click on this face > Texture > and check "Projected". You will not notice any change at this point.
Now edit your terrain group (double click on it), select the Paint bucket tool and press the Alt key - it will turn into a "sampler" (or "eyedropper") tool.
With the Alt key still pressed, sample the projected material from that rectangle outside your terrain group
Release the Alt key and click on your terrain mesh with the paint tool - your image will now be nicely projected onto this terrain.
The whole idea of using a separate rectangle lies in point 3 above. You can simply not position a material on a curve surface properly. You can turn on hidden geometry to position it on one facet at a time but that way it is not really accurate visually since your material is only "moving" on this current facet - so introducing this temporary, "helper" geometry will speed up the whole process and allow you to work acurately, too.

mitcorb

Hi, Gaieus:
I was kind of waiting for Monks to reply before I posted. But this thread sank to page 2.
I want to commend you for your dedication to things like this. Your effort to help Monks has helped me, and countless others. You have presented the technique very clearly here.
Thank you, again.

Gaieus

And it is fully of typos as well.

mitcorb

Well, one other thing I have learned while participating in this forum is the ability to see beyond typographical issues, unless it significantly garbles the message.

monks

Wow, thanks a lot for this. I'll give it another go later when I get home following your instructions. Yes, I found quite a number of posts on this but the solution seemed to be something of a moving target as things have changed over time. I'm using drape in the sense that it's used in the GIS industry (as opposed to 3D modelling)- draping a texture over a heightfield (I guess that means orthographically projecting a texture onto it). The draping of geometry sounds very useful too.
I did try to do this but I had trouble setting up the rectangle, but I've learned a few more things since then. Another problem I may have is that some of my models placed onto the terrain have become grouped somehow with the terrain mesh- I posted about this elsewhere. I may need to resolve that issue first. Dunno.

monks