April 19, 2017 at 6:51 am #103191
Quick question, is this a good projector for the AR Sandobox?
BenQ MW526A 3D-Ready DLP Projector
– 1280 x 800
– 3,300 Lumens
– 13,000:1 Contrast Ratio
– D-Sub, Composite Video, HDMI, S-Video, USB, Speaker
This one is about 1/2 the cost of the recommended Benq MX631ST.
ThanksApril 19, 2017 at 6:33 pm #103193
Generally speaking, the recommended projector is relatively expensive because it is a short throw projector and it has a native aspect ratio of 4:3.
I have no personal experience with the mentioned projector, but quickly checked a projector calculator. It seems with the standard dimensions of a 75 cm by 100 cm Sandbox the projector would need to be 2m above the sand surface. I think this is not an option in most rooms, not to mention the kinect sensor needs to be mounted about 1m above, so it would be in the way.
If you already have this projector laying around or for whatever reason insist on using it you could theoretically use a mirror to split the path of light in to two parts. To avoid interference with the kinect, mount the mirror next to it at 1m above the sand and the projector 1m away from it, either horizontally or vertically. The later would mean mounting the projector to the Sandbox looking up which could mean it would get dirty very quickly. Keep in mind that the mirror needs to be a minimum of 37,5 cm by 50 cm for a 50/50 split, add to that room for the trapezoid distortion (keystone) depending on the angle.
Another potential problem is that the cheaper projector has an aspect ratio of 16:10, the kinect and therefore the ideal sandbox is 4:3. This will lead to overprojection, which could be an issue.
We are building an AR Sandbox using a mirror right now, but our projector only needs 1,3m meters of distance. If you want we can keep you updated on how the mirror setup works out for us. Overprojection does so far not appear to be a noticeable problem however.
greetings from Germany,
DavidApril 20, 2017 at 10:57 am #103194
Thank you for the reply, much appreciated.
We have not purchased a projector yet. We are not-for-profit so funds are limited. Would this be a better option? http://www.projectorcentral.com/BenQ-MW632ST.htm
Do you have any recommendations for short throw or 4:3 projectors?
Which calculator are you using to determine which projector would work?
thanks againApril 24, 2017 at 3:54 pm #103197
I´m sorry I kept you waiting over the weekend.
As far as i can see the MW632ST you linked is just as expensive as the recommended MX631ST and its 16:10.
Going by the name and the datasheets they seem to be pretty much identical otherwise (comparison).
For the throw calculation you can use pretty much any online projector calculator as they all use the same projection angle and min/max distance data from the manufacturers official datasheets. As a matter of fact, you can just use sin(x) to figure it out yourself 😉
I have no idea which projectors can be bought cheaply where you live but generally focus more on the brightness (lumens) and the minimum projection distance and the according image size. Since the kinects resolution of 640 by 480 pixels is the limiting factor, projector resolution really does not matter as much. See the official instructions for further suggestions.
I do however have a few more tips for a budget build:
– Buy used (or ask around at schools, they tend to have older projectors the want to get rid off, usually plenty bright ones! Short throws will be rare though)
– do you really need water simulation? if not almost any old computer will do
– find someone with a workshop who is willing to support you. Tools are expensive and good equipment and experience will make the build so much easier and quicker
– perhaps reclaim wood, again, ask around if someone has some laying around from building a shed for example
– don´t use kinetic sand, its expensive and not really needed. Just buy regular playsand and get it a little wet if needed (cost us 4€ for 50kg). You might want to wash it first as it can be very dusty otherwise.
– perhaps find a sponsor (local computershop for example). The AR Sandbox looks cool and companies will want their name on it. Don’t forget to acknowledge the creators of the original project, KeckCAVES, and the government grant they got. Find the suggested plaque here
I hope that helps!
Sorry it took me so long to reply,
April 24, 2017 at 4:22 pm #103200
- This reply was modified 3 days, 1 hour ago by David.
P.S. I just found this thread from a few weeks ago,
one user (Frank Conforti) says he is using the MW632ST (the one you mentioned) successfully but is now looking for a cheaper option for a private install. Perhaps you can ask him which projector he ended up using.
The thread should be just what you are looking for as Oliver explains some issues that are important for you.
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