Confused Why Image Stretches after "Joining"

Hi, I have created a plane object 2 wide and 4 tall. I then created an image 2 wide and 4 tall. I then made a texture and mapped the image onto the plane object using mapping type of “Generated” and “Flat” and it looked great.

I then duplicated the plane and then "joined the two planes together. The problem is when I Joined them together the image now appears stretched wider and is no longer looking like it did before I “joined” the planes. I may unwrap the plane but I still don’t see why Joining would “Stretch” the texture when it looked fine before I joined the planes.

Any ideas why this is happening?

pg

When you Join the planes, you’re making a single plane twice as wide as the original, and mapping to it a texture made to fit a plane half as wide as it now is – it has to stretch to fit the new plane dimensions.

If you are looking to have the texture repeat (tile) across the new wider plane and preserve its original proportions, you need to set new texture mapping specs to do so.

Thanks Chipmasque. I am joining the planes in a “X” shape so I didn’t think it would map across both planes but I understand if the object is “Joined” then the mapping reads it as “one” object instead of 2. So this problem will occur even if I UV unwrap the plane before Joining it?

pg

UV unwrapping should be done only after a mesh is finalized imo – not sure what the results would be otherwise but I’m pretty sure the UV maps wouldn’t be seamlessly melded (if you’ll pardon the obscure pun :wink: ).

All texture mapping is based on the final geometry/topology of the mesh, so if you change that in midstream (Joining does that), it kind of invalidates any previous mapping efforts. How much it affects the mapping depends a lot on your model and how the textures are mapped.

One thing to consider is whether you actually need to Join the meshes – they can be separate Objects (and actually share the same Mesh datablock if that’s useful for your model) and still be made to move together by various means – parenting, constraints, etc.

Thanks Chip. Actually I’d like to keep the planes separate, but it becomes problematic when using as a particle system, but I will try it. If only “Parented” objects could be appended. Sigh! :frowning:

pg

I think you will need a single mesh for this, so you may have to do the Join and just leave all the UV and/or texture mapping until you have a final object to use as your particles.

Thanks Chip, actually I just tried it and using “Groups” works great, although I still hope the Blender Team can allow “Parented” Objects to be appended in future updates.

pg

Excellent! I’ll have to remember that for future use myself.

From the poor computer’s point of view, when you “join” two things … well, they (obviously) become “one thing” that is now “twice as big.” The poor-computer will therefore try to make an appropriate adjustment – hence, the “stretching.”

It makes not the slightest difference to the “poor computer,” though, if instead you treat the two (distinct…) objects as a group of two objects. (i.e. “whether the distinction is visually apparent to the audience or not.”) And, as it happens, “it also makes not the slightest bit of difference to the audience, either.”

As suggested, the latter view (“two objects”) is probably much more appropriate. The computer no longer considers that it has to “stretch things,” and “the audience will never know.” And, hey, we don’t have to satisfy the computer! We only have to satisfy the folks who bought the tickets . . .