Mapping to a curved shape

[Jeff Bell]

I'm attempting to map a JPG image to a curved shape (a portion of a ship hull). Given the irregular shape, I can't get a decal to work. So instead I've created a material with the JPG as a texture map and sized the material to fit the length and width of the shape exactly, expecting to just need to adjust the offset  bit. However when I render, the graphic looks fine on the vertical surface, but then gets rotated as the surface turns under.

I've tried surfaces made from a polyline with a thickness and a swept surface and have tried rotating the texture map in the material definition without success. Attached are screenshots of the surfaces, the JPG to be applied, and the rendering results. Any ideas?

Thanks in advance.

[Roy Hirshkowitz]

This can be really difficult (or impossible) to do using "canned" mappings-- it's probably a good application for UV mapping using an application like Blender and exporting via an obj file.  UV mappings store the textures coordinates on each mesh vertex so you can usually get what you need-- although the UI can be difficult to work with.

It would help if I knew what the thing was supposed to look like.  It's possible a cylindrical mapping might work OK for this geometry.

[Jeff Bell]

Thanks, Roy. I thought about trying to simplify the shape into a quarter of a cylinder, but it needs to be the actual shape of the hull. I also thought about learning Blender or TruSpace, but need to have the exhibit done soon. I might give SketchUp a quick stab, again creating a material from the JPG and seeing what happens.

The finished image needs to have the two brown circles hitting at the midpoint of the hull, horizonally at each end, just below where the mapping gets out of whack.

When I tried rotating the JPG, everything on the underside of the hull looked fine, but the vertical surface got rotated and weird.

May have to go with a Plan B for this assignment.

[Roy Hirshkowitz]

In general, you'll want to be adjusting the mapping attached to the object rather than the material-- it's much easier.  Use the Quick Mapping option on the Material page.  You can easily specify an origin point and orientation.  The default mapping is called box mapping-- you may able to split the hull and use two planar maps instead if you can't get a box map to work.  Send a drawing with the hull and someone may be able to take a shot at it.  I'm out of town for a couple of days so it probably won't be me.

[Jeff Bell]

Got the planar mapping to work. I didn't expect the flat image to map around the hull correctly, but it turned out pretty well. Only minor distortion, but not enough to worry about. Thanks for the guidance.

[Roy Hirshkowitz]

Great.  Send some images of the finished product if and when you can.