#flat mirror
12 messages in this thread
I have made an auto-reflect material with Flat mirror option, but it does not
seem the objects that I need. Is there a particular angle of lighting that
makes it work?
Andrey
One of the most common reasons for apparent failure of Automatic Flat
Reflection maps is how they are applied, Andrey. For a AFR to work properly, it
should be applied at the face level to a single, flat face or a selection set
of connected, flat co-planar faces of the same object.
The complete explanation is found in the Reference Manual starting on page
9-63.
Hope this helps,
-Alan Iglesias
Alan, I did apply the material to the selection of coplanar faces. Sometimes,
it works, sometimes it doesn't, that's why I wondered if the angle of lighting
influenced anything.
Andrey
I'm not sure about the angle of lighting in particular, but I have seen
unexpected results with *camera* angles that are very small in terms of degrees
over the reflected surface. Maybe GaryY can elaborate…
-Alan
Depending upon how the flat mirror is clipped, if you get to within a degree or
so of the surface, there might be some extra clipping going on. (but it's
extremely rare)
– G
Gotcha.
Thanks for the clarification, Gary.
-Alan
Andrey;
When using auto-ref you need to light up that which is being reflected, not
that which reflects, does that make sense? (g) May be that is why under some
lighting conditions it works and under others it doesn't.
Zac (AZ-TECH)
Berkeley
Are you moving the camera at all between the times the flat mirror works and
the times it doesn't?
Michele
> Are you moving the camera at all between the times the flat mirror works and
> the times it doesn't?
Well, it is a still picture, but I think I moved a camera to a different
position.
Andrey
>>I think I moved the camera to a different position.
Aha! This may be the problem.
In order for the camera to "see" the reflection, the camera and object must be
arranged at appropriate angles to the reflective surface.
In the picture below, the object and camera are at the same angle from the
perpendicular of the reflective surface. This will give you a reflection every
time.
object camera
o perp. o
\ /
\ | /
\ | /
\ | /
\|/
——-o——— surface
reflection
The angle off the perpendicular is called the "angle of reflection" in optics
theory. You will get a reflection as long as the camera and object have the
same angle of reflection. This means you can move either the camera or object
further away and still get a reflection, as long as they maintain the same
angle off the perpendicular.
Flat mirror reflection is pretty forgiving about this — sometimes you can be
miles off the angle of reflection and still get a reflection. Regular
autoreflection is merciless — you have to be exactly perfectly on the angle of
reflection to get anything at all.
A full explanation (with better pictures!) is in the new 3DS Tips & Tricks
Series book called Glass & Reflection, $25 from Delmar Publishers
(1-800-347-7707). It also has exercise illustrating this exact point.
Hope this helps!
Michele
Do you have any objects that penetrate the AFR faces?
Bruce Meikle
WZMH Architects
> Do you have any objects that penetrate the AFR faces?
No, I don't think so.
Andrey