I’m new to mental ray so go gentle.

I’m trying to light an interior scene with just the glow from a tv. I’m using the mr arch design material and have my video in the self illumination slot. The trouble is that in order to get enough light into the scene, I have to set the luminance way high, but then the image on the tv blows out.

Is there a way to have the luminance that effects the scene up while keeping the self illumination on the material itself at a reasonable level?

Thanks

--
James Kelly
fo co mo so

You could place a rectangular Area light over the screen, put the video in the Projector Map slot (or a blurry version) to colour the light.

I don’t think the projector map is even necessary.  Just adjusting the color of the light to a bluish tone should be enough.  If you use the map as projector, you’ll have to blur it a lot.  Like a Photoshop blur, not just with Max’s blur under Bitmap.

3DS Max Design 2011 64-bit - Advantage Pack
Dell Precision T5500, Dual Six Core Xeon X5650 @ 2.67GHz, nVidia Quadro 5000, 24 GB RAM, Win 7 Enterprise 64-bit
Minneapolis, MN, USA

Yes, it would depend on the look of the video footage. If it’s fairly vauge without a lot of strong colour, that would do.
If it contains a lot of colour that changes over time, you may want the map. Eg, a green field under a blue sky, then a red car drives into frame and fills the screen, the colour of light from the TV will change.
If you go for the projector map, make a lo-res heavily blured copy of the footage with a compositor/editor, or batch process the frames in PS.

If you want to do it “properly” without using an area light, check your final gather settings… you’ll need quite a lot of rays (so that some of them actually hit the TV screen) and I’d add a few diffuse bounces. Also, most importantly, disable the FG filtering because otherwise it’ll discount the few rays that did actually make it to the TV screen.

Even after that I think you’ll still find it’s very dark in the room, so the area light is probably your best option (and that way you can enable GI photons and have the light bounce around the room properly without having to wait for hours of FG calculations).

Either that, or get yourself a copy of V-Ray and use the Light Cache.

All good suggestions.

The footage is of an 80s home video game and we’re trying to have as much of the colors and movement in the room as possible so a blue tinted light won’t work.

I tried the projector map and it’s close, but as was mentioned, it’s too sharp. Blurring the footage outside of max might do the trick.

So far the best solution I could come up with was to bump the fg multiplier way up (10.0) and leave the screen surface luminance at 1.0 (units). This seems ok, but when I went to add a few more fill lights, I had to pull their intensities way down.

My next thought was to have two screens, one that throws light into the scene that’s invisible to the camera and one that has the self illumination on it. Is this even possible (to have an object that throws light but isn’t rendered itself)?

Thanks for the help.

--
James Kelly
fo co mo so

Is this even possible (to have an object that throws light but isn’t rendered itself)?

Yes, just go intp Object Properties, via the Right Click menu, in the Rendering Control section, uncheck Visible to Camera.
But, that will effectively do the same as having the area light, but less render efficient.
The area light is throwing out Direct illumination, much quicker and easier for Max to render than dealing with indirect illumination from FG.
There should be attached a simple scene setup (Max 2010 file).
The render was done with FG off for the screen material SI, so the light comes from an area light.
The scene FG is on Draft setting with one bounce, it would have to be set way higher to get comparable results with the lighting form SI FG alone. Don’t wast time, use direct illumination where you can.
The projector map was blured within max, blur:10 blur offset:0.2

	Attachment
tvroom.zip

	Attachment