Bump map flip flop
9 messages in this thread
I've just run into the annoying habit of the renderer to
reverse the effect of a planar projected bump map as it passes
through the center of an object, leaving one half of the object with
a reversed bump map and a seam right down the middle. The object I'm
working on has to be planar mapped, and I've tried placing the map
icon dead center and making the material 2-sided, but to no avail.
Aside from detaching the faces into a separate object and mapping
from the opposite side (or making the bitmap negitive), which I'm
about to try, is there an easy workaround to this problem? Was this
the way it was designed to work, or was it just an oversight? Help!
Bump mapping just works that way. As the planar map passes to the opposite
side, the UV's are reversed. If you want to map through an object without
getting that effect, you've got to split it, flip the mapping coordinates, and
then map it from the back.
– G
>>you've got to split it, flip the mapping coordinates, and then map it from
the back.
I had already tried flipping the coordinates and applying it to one
half, but I couldn't seem to get it right (the bitmaps would have to be flopped
for that side as well). I did however work it out. What I ended up doing was
splitting the object, and without touching the map coords, applying a second
material to one half. The new material is identical to the first, except in the
bump map options, I hit the negitive button. Works like a charm.
The only drawback is having to manually weld the verts back together to
get the smoothing back across the split. Not that much trouble for this object,
but I've got another large, complex model that that needs several different
mapping coords applied to various parts, but it needs to remain a single, solid
object because it's entire surface has to be smoothed. It can (and will) be
done, but I've got alot of welding ahead.
I've got a few wishlist items on that subject, but I'll save them until
4/1.
David
David,
With R3 you DON'T have to split the object and apply different mapping –
Simply apply the mapping coordinatec ONCE and apply a differnet MATERIAL to
the reverse side – this material would be identical to the first except the
bump map is given a NEGATIVE parameter (innies are now outies). No more
memory consumption because the same bitmap is used twice and most
importantlly the object is still welded. Works great – try it.
– Phil
I had already figured the negitive part (see my reply to
Gary), but I have been dealing with mapping so much lately that I
didn't even consider applying the second material to the selected
faces without splitting it into a separate entity first, because its
stuck in my mind that you can't apply coordinates to selected faces.
I forgot you CAN apply a material. Of course I already did it
lastnight, but it only took a few minutes to split, reasemble and
reweld. However, this does not help with the large mesh I am about to
get back to, as it needs different materials AND coordinates applied
to the limbs. So I think I'd better light the torch and put on the
welding goggles.<g>
David,
Be careful about welding previously mapped meshes – the faces that are
welded will have their mapping distorted to some extent. The only
reason to weld is if you need the surfaces to smooth over one another
(or work in an animation together). Always a tough nut – best of
luck!
Phil,
That's why when splitting an object for mapping purposes, I NEVER move
anything. That way, when its welded back together, no faces are stretched.
Regarding smoothing, thats become a source of alot of headaches (and work)
lately. Maybe I should just stay away from the "organic" models…. Nah! That
would make life too easy!
Thanks for the tips.
David
You probably know this, but mappping coordinates can become distorted
without any actual mesh movement once a (single) vertex weld has been
made. Now if we could only acquire mapping from the face level, or
at the very least the element level, and be able to apply it at the
face level we would be in ok shape. BIG wish list item that I think
all would agree on and has been a constant modeling headache for the
last three years. Organic models? Actually it sounds like fun!
Phil,
>>You probably know this, but mappping coordinates can become distorted without
any actual mesh movement once a (single) vertex weld has been made.
Actually, I didn't. I havn't noticed that on the quick tests that I've
done, but thats probably due to the high face detail in combonation with low
map detail in the weld areas. I hope it doesn't become a problem, but I think
it'll be fine.
>>Organic models? Actually it sounds like fun!
Actually… it is! <g>