#SHADOW casting quest
18 messages in this thread
So I was wondering about casting shadows in 3DS. I have a tube with
the ends cut out. I have placed a blue light in the tube and placed
the target ust inside the end. I then created a "wall" and placed it
a few feet from the open end, infront of the light. The light is
blue. The subsequent rendering shows that the wall is all blue. Why
is that? Shouldn't the tube "cast" its own shadow and made a round
shadow on the blue wall? I know I can just reduce the falloff/hotspot
to the size of the end of the tube and get the same effect, but I
just wondered if an object can cast shadows from the inside out?
>>blue light special, inside tube…
James,
In 3DS, only faces with their normals towards a spotlight will cast shadows.
With your light inside the tube, all the face normals are away from the light,
so the light shines right through. You can fix this several ways:
1. Render with "Force 2-sided" ON. Not the best idea, but easy.
2. Make a second tube inside the first tube and flip its normals
with Surface/Normals/ObjectFlip. A better idea.
3. With the materials editor, make your tube's material 2-sided.
I like this idea best.
All this is assuming you've turned "Casts Shadows" on in the Spotlight
Definition dialog. (ouch!, sorry…) <g>
JKJ
Hey John,
But I still can't get this to work. Let me open it up a bit.
I have a scene where a blue light (nightlight) I shining through a
window. The window has cross beams and I want the pattern of the
beams to shine on a wall and a painting perpendicular to the window.
When I shine the light through the window, only the painting is lit,
whereas the wall doesn't take any of the blue light. Everything is
set for shadows and recieving shadows. The weirdest part is that the
wall doesn't take any of the blue light, whereas the painting in the
wall does…
Hey, didn't you say a while back that you didn't have 3DS??
James
Did you EXCLUDE the wall by accident? Perhaps the material you used for the
wall does not "reflect" light that well. I've found some materials show up
better than others when the light is dim and cool.
Do shadows show up on the painting (is the light aimed properly, and the
picture in the correct area to recieve shadows)? If not, try a projector
light, or a cookie. If they show up on the painting and not the wall, then try
remaking the wall, or giving it a different material.
John Tissavary (La Luna cie)
No, the wall isn't EXCLUDED. The material does reflect the bluw light because
when I turn on the OVERSHOOT, the who wall is blue. But without that, only the
picture gets bluw. And when I move the crossbeam, I do get a shadow on the
picture, but still no light on the wall. I mean, if the light is getting to the
picture, shouldn't it hit the wall on the same vertical plane?
I'll probably have to create a cookie, but it doesn't make sense. This way
_should_ work…
Thanks John James
Why don't you creat a another higher intensity blue light that excludes the
picture, but brings the wall up to the light level you need?
John Tissavary (La Luna cie)
John,
Excellent idea, kinda like Richard Edlund's dc powered fluorescents at ILM in
the late 70's. It theory, it should work well for him.
Paul
Edlund's quite a creative/technical genius in my book. I hear BOSS FILM is
expanding their CGI quite a bit. Didn't they do a couple of huge animations
for some hotel in Vegas recently?
John Tissavary (La Luna cie)
John,
You know….. I'm not really sure. There is sooooo much stuff going on in this
industry at the moment that I no longer keep track. I do remember seeing a
sequence of the Vegas animation you're talking about but I don't remember who's
name was associated with it. Boss did do the "Journey to Technopia" which was
touted as the centerpiece of Expo'93.
I've always been a big fan of Edlund, I was a child when he won his oscar for
Star Wars, and I thought he was nuts to leave Dykstra and the ILM crew. But
hey….. 10 years later Boss Film is quite the achiever.
You know now that I think about it….. when did EEG become Boss Film?
Paul
P.S. – I figured Edlund would rank high in your book, above all else, he's a
phenomenal film and lighting genius. Seems to really love 65mm stock.
I got to work with Dykstra a bunch of years ago when I was doing special
effects modelling for a feature film. We hired his company to do the opticals,
and boy did he do them. It was fun to watch someone work who didn't always ask
a million questions about everything. He just looked at the story boards, the
specs we handed him, and the set, and went to work for a couple of days with
his camera operator.
I'm not sure when Boss became Boss, but it was quite a few years ago (mid-80's,
I think).
John Tissavary (La Luna cie)
Sorry, John, I've been posting only part of the story each time. It's not so
much that the wall doesn't get lit – it does, if I move the light just a whit
(?). It's that the shadows of the crossbeams won't fall on the wall – only the
picture. I can't figure it out – it doesn't make sense. I guess the only thing
to do is remake the wall and see if that does it. Hey, do some materials not
take shadows?
Thanks James
PS: AHA!!! That last question started me thinking. When I was doing test
renderings earlier last week, I was checking for proper shadows but couldn't
for the life of me get the shadows working. Anyway, as it turns out, I was
rendering at FLAT – shadows need PHONG! And guess what? The "paint" on my wall
was… GOURAUD! That's why the wall wouldn't take the shadows! Well, that was
very cool. Thanks for you help, John!
James
I can't tell what the problem is without seeing it, but why don't you just use
a projection light and be done with it?
– Jack
<<I can't tell what the problem is without seeing it, but why don't you just
use a projection light and be done with it?>>
Well, it was more than just the effect. It didn't make sense that the columns
wouldn't cast shadows. And I hate cheating when I don't have to. The amount of
work needed to set the cookie properly in relation to the columns would have
been the same for just working this one out. As it turns out – the wall have a
GOURAUD shading – ooops! No shadows there. A simple click of a switch and
everything works fine.
Thanks
James
Glad you found it James.
– J
JT,
Whoa! You went from a tube to a window pretty quick. No matter, we are a
multi-OBJECT-ive support organization here!
>>Hey, didn't you say a while back that you didn't have 3DS??
ACK! ACK! ACK! I am JOHN _K_ JORDAN, JKJ, not to be confused with an impostor
on the forum with a similar <great> name. Now you've made both of us mad! <g>
Apology accepted. I've been using 3DS for some time, having logged several
thousand modeling & keyframing hours. Of the 17 John Jordans on CIS, you'll
find two here. (Just check for the JKJ signature (with additional appologies
to poor J.Foust!)). I've been so busy with work the last few months I've been
mostly invisible here, but I indend to take it easy & play some for the next
few weeks.
First, did you get the tube/light to work properly? I made one to test and the
shadow worked just as you were asking.
Second, for your wall/window/picture problem: if nothing is excluded, it should
work. I duplicated your geometry just now based on your description and it
works here. Are you using all the standard, default spotlight parameters? Are
you sure your light is positioned OK? BTW, if you don't need to show the
window in your final view, a projector light is a great way to do this.
If you are under a deadline and can't get this to work, E-MAIL it to me at the
above account # and I'll be glad to take a look at it.
JKJ (repeat, jKj, the elder, not JNJ, 20 yrs the younger <g>)
Hey John,
Ooops! Well, cyberspace can be a confusing place, especially when nobody has a
face <g>. Very sorry for the mistaken virtual identity!
I wish I could describe this scene to you a little better… A spotlight
shining through a glass material (??maybe this is a problem?? Nope) onto a wall
with a picture hanging on it. The light is shooting through at a 45 degree
angle. In the window are two tall crossbeams. When the light shines through the
window at the wall, the whole wall is lit up blue, but no shadows. But the
picture does have a bit of the shadow – it just doesn't travel past the bottom
of the picture.
I know this is a little different from yesterday – I'm bigtime stuck. Maybe I
will take you up on the upload, just to see what your fiddling results in…
Does it have anything to do with the SHADOW SETTINGS? I've read the 3DS manual
ten time and still can't get a good grasp on what these settings do.
Thanks John James
JT, >>no window light on wall…
I made an identical scene (the best I could, from your description), and I
could not duplicate your problem of "no light on wall until overshoot". I
tried many combinations of light, shadow, and material attributes. Is your
wall set to accept shadows? Did you try recreating (perhaps a simplified
version of) your scene in case something got corrupted? (very rare, but
possible)
I would really like to see your file. BTW, don't upload to the forum – just GO
EASY and upload as a binary file and send to my user ID. If the file is large,
it will be cheaper for you if you delete anything that is not relevant.
JKJ (who'd rather debug than anythang)
Hi John,
Hey, thanks for the help and the work at trying to recreate my problems. What a
guy! But, as it turns out, the material I was using on the wall was a GOURAUD
shade – gotta use that PHONG to get shadows! Oops..
Thanks again for all you thought. I owe ya. Needless to say, don't expect the
file…
James