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I'm trying to model a following scene: enter image description here

It's a project of a simple DIY projector:

  • on the left, there's a smartphone or just something with a light-emitting display (LCD, AMOLED). Just to clarify the model: it can display various images, not just emit plain white light,
  • in the middle, there's a lens which has a certain factor or refraction,
  • on the right, there's just some matte (like a wall) surface where the image from the LCD should be visible after passing through the lens.

I'm a beginner in 3ds max when comes to raytracing stuff. I know how to model the placement of the elements, but I'm not sure how to configure the whole raytracing thing in order to make it work like this. Please give me some general pointers, e.g. what kind of surface I have to set to make it emit light (in fact, it should be a light-emitting texture? not sure) and also what kind of material/surface to choose for "receiving" light.

  • As an experienced 3D artist I'd fake it, unless you wan't to wait 50 years for it to render. – GiantCowFilms Feb 4 '15 at 16:20
  • A smart phone will never work as a projector, it simply isn't strong enough. Try (carefully) looking into a beam of a projector.... WAY brighter then you're smartphones screen... – GiantCowFilms Feb 4 '15 at 16:25
  • Do you have measurements for the placement of the objects [Location, scale, refraction & shape of the lens]? I seem to get an out of focus image, And I think it may be due to an incorrect setup. – GiantCowFilms Feb 4 '15 at 16:34
  • @GiantCowFilms thanks for your feedback. Perhaps I didn't make myself clear: basically I want to create a realistic physical simulation of this phenomenon, like a optical bench. This idea already works, but the visible image is quite dark (looks fairly ok in complete darkness) and with screen brightness set to maximum - imgur.com/a/wR2Xf . The 3D simulation doesn't have to be high-res, I just want to experiment with different setups and parameters of the objects. Rendering times around a few hours are ok, so I think some raytracing or radiosity would do the trick. – PiotrK Feb 4 '15 at 22:53
  • @GiantCowFilms parameters - distance form the phone to the lens: around 10 cm. From the lens to the wall: around 2 m. Lens is 7 cm in diameter, I don't know how to measure its focal length. When the simulation environment is ready, it's just a matter of trial and error till you get something in focus. – PiotrK Feb 4 '15 at 22:55
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Disclaimer: I was unable to get a sharp image with identifiable forms

In theory this should work:

  1. Reconstruct your scene exactly: Everything needs to be the same distances shapes and sizes. You can use units:

enter image description here

  1. Materials:

    • Wall: you can leave it as a white diffuse surface. If you wan't you could add a bit of reflective shader, or even a realistic dry wall shader, but that isn't necessary.
    • Phone [Projection surface]: Simply UV unwrap the plane, and add this material: enter image description hereYou may need to tweak the emission strength depending on how bright you wan't your image.

    • Lens: You may jump to the glass shader, which would work, but for efficiency while rendering, I would use the refraction shader. Set the IOR to the same for your material, you should be able to look that up online, assuming you know what exactly your lens is made of. If you don't have such data, trial and error can work to.

  2. Render setup: You should find your most powerful computer, preferably with a good GPU. Set the render device to GPU (Very detailed steps).

Finally set your render sample to a number around 10k, hit F12... and wait for the magic

Best result, at 10k samples:

enter image description here

Note the image is mirrored horizontally, I countered the vertical mirroring by scaling the plane -1 on the Z axis, I would have to do it again on the X axis. This is a sign that it is working correctly, since a lens will mirror an image both ways.

Projecting this image: enter image description here

.Blend file

  • Wow, thanks a lot! I'll check it out tomorrow, it requires some time to configure it all. Could you please share your Blender project? – PiotrK Feb 5 '15 at 17:00
  • Sure, uploading... :D – GiantCowFilms Feb 5 '15 at 17:04
  • @GiantCowFilms You did you do a inverse gamma on the picture and then back after rendering or it will report different form reality :) Anyway the energy is easy to compute, if the image is 2 times larger per side (thus area of 4 times more) then it has 1/4 of the original energy thus 4 times dimmer which is a lot considering human eye is on a gamma curve – joojaa Feb 5 '15 at 17:19
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    @GiantCowFilms After some experimenting and calibration, I got this render: i.imgur.com/vz0EPbd.png (original: i1-win.softpedia-static.com/screenshots/MonitorTest_2.png). There was one serious problem with your scene: the lens wasn't spherical. I mean, the convex part you probably made of a half-sphere with radius of 6cm, flattened so that it would be 1 cm thick (here's a little explanation: i.imgur.com/pHm9tBA.png). After this correction and a bunch of tests with different IOR, I got this render on IOR 1.423. Thanks again for your help - it works! :) And it's fascinating! – PiotrK Feb 7 '15 at 9:34
  • @PiotrK Ah, Good catch!!!!! – GiantCowFilms Feb 7 '15 at 14:41

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