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This tutorial will show you how to use Poser 5 lights to simulate a projector, such as an OHP or cinema projector.
This tutorial assumes a basic knowledge of Poser 5 and a suitable graphics program. Photoshop is used for illustration.
So here is the scene set-up I have chosen - A plain projector screen, which is the Poser one-sided square (under Props > Primitives) and its 'legs' are made from two Poser cylinders (Props > Primitives). I've put another square at the back to simulate a wall, and turned on the ground plane, so that you can follow what I'm doing. This is just the default lighting at the moment, we'll be changing that in a minute. I've added Posette just for scale reference, but my, doesn't she look happy with that cane in her hand? *G*
Now we need to remove all the lighting from the scene (it's easier than changing the existing lights.) You can click and delete them manually, or you might want to download the very-useful Python script for light changing, available in the Renderosity free stuff by Ockham.
When you've deleted all the lights, click the little bulb symbol next to the light controls to create a new spot-light.
Now open the Properties panel for the light (Object > Properties) and change the rotate values so that the light is pointing dead ahead. Also change the trans values - I have put it in the centre of the room (because my screen is also centred) and bring the y_trans to about half-way up the screen, and about half a poser unit back from it.
Do a quick render to see how it comes out. I ended up moving my light down to about 0.475 units to get it centred on the screen vertically.
If you are going to move your screen around at all, it's a good idea to parent this light to the screen, so that it will follow.
Now we need to fiddle around with the values at the top of the light properties to get the effect we want.
The first value we need to set is Angle_end. This figure represents the absolute outer edge of the light cone. At the moment, as you see above, the light is very soft around the edges. This is because the default angle_start is set to zero. To get a sharper light source (which is appropriate for a projector), we'll want to change it to something closer to the angle_end value. Let's try setting the angle_end to 60 and the angle_start to 50 and see what happens.
As you can see, we have a sharper image now, but the light is also illuminating the wall behind the screen (something we couldn't see clearly before when the light cone was soft.) That's okay, we will deal with that problem shortly. But we want our cone a bit bigger, to take in more of the screen. Let's set both values to 80.
I also decided that the wall was too far away from the screen, so I have moved the wall prop forwards on the z-axis.
At this point you might be wondering why Posette is almost completely in shadow, but the wall behind her is illuminated? The reason is because she is actually in front of the light cone, except for her arm where it goes across the screen. Here is a shot in preview mode where I have changed the camera angle so you can see the light position better.
This isn't a problem because we will be mapping our light to appear within a box on the screen, eliminating the overspill. Once we've got that done, we can add in other lights to the scene so poor Posette won't be in the dark :)
OK, we're now going to go to our paint program and make the image that will be projected onto the screen.
I've decided to immortalise my shopping list. I've made it at size 512×512. Poser always applies the image as a square, so it's best to use a square template. I'm guessing at the size, we will see what happens when I apply the texture in Poser. I'll probably have to change the size a little. (I've put a small border around the image so you can see it clearly on screen - this is just for the purposes of the tutorial.)
Now in Poser, with the spotlight selected, go into the material room. Drag a node from the color through new node > 2D textures > image map.
It's pretty obvious that my map is too large. However, decreasing the map size isn't going to help on it's own - what I need to do is add borders around the text, so that there's more white space around it. I'm also going to delete the first couple of lines on my “list”. Then I'm going to reduce the size back down to 512. However, if you're using an image, you'll want to probably start from scratch, or you'll lose resolution.
After reducing my map so that it fits onto the screen, all we need to do is make a mask to get the light into the shape that we want. The method for this is basically the same as a trans map. We're going to make a black and white image in Photoshop (or other graphics program) and apply it to the Intensity node in the material room.
I want my projection to be square so I'm going to start again with a new image 512×512 pixels. Now, because I want my projector to be quite close to my text, well within the screen, I can cheat here I put a new layer on my texture map (mine's called shoppinglist.gif) and draw a border around the area I want visible. (Just like making a trans map.)
Then I invert the selection and fill it with black.
Now I drag the layer from this image over to my new 512×512 image and make sure it's centred. Then I can save that image as a gif. I've called mine just “trans_1.gif”.
Now let's see how it looks in Poser. Again we drag a new node through to 2D textures > image map, this time from the Intensity node.
Now we're close to what we want. But I'm still getting backsplash on the wall, which I don't want. I'm going to tighten up the borders some on the top and bottom, and also feather it slightly for effect.
I use the same method to do this as I described previously - draw a border around my words, but make it tighter this time, and feather the selection before filling. You may also need to go back to the light properties, and change the size of the spotlight.
Let's see how this looks.
Perfect! Now I can add a few more lights at low intensity, so poor Posette isn't standing in the dark anymore.
That's it for the main part, but there are a couple more tricks over the next two steps…
Now, suppose I want to change my shopping list to something more exciting, say a holiday snap? And perhaps I want to make it as if viewed through an interesting frame?
First I take my picture that I'm going to use and check its proportions. I need to crop it into a square shape, otherwise it will be distorted.
Then again, I make a new layer, and draw a solid shape in black over the area I want to be visible. Then drag that layer into a new document of the same size as my photo. I flatten the image, then invert it so that the shape is now white on black.
Back into Poser, and connect my photo to the light's Color node, and the black and white shape to the Intensity node. Voila!
That is my little boy, by the way
Just one more thing to show you…
OK, just one final thing. Suppose you want to take your shot from an angle, and see the beams of light from the projector on their way to the screen? You can do this with Poser 5's volumetric lighting feature, and we don't need anything else to do it.
Go into your light properties, and set the “Atmosphere Strength” parameter to 1.0. (Note: this parameter only shows up if you have installed service release 3. If you haven't applied SR3, go and get it. Poser 5 runs a lot more reliably with it.)
Now back into the Material Room. Select “Atmosphere” from the drop-down list…
And set the boxes up as above.
The important value here is the Volume_density: I started at 0.01, but my render didn't show the effect very strongly, so I put it up to 0.02 for the purposes of this tutorial. However, for a normal render, I'd probably leave it at 0.01.
Then go back to the Pose room. Adjust your camera angle as desired. Check your render options - you need to use the Firefly renderer, and you must have cast shadows checked. You also need some kind of background prop for the effect to show against. It won't render just over the background. I've put another one-sided square in as another wall. And here we go:
And that's it! I hope you enjoyed this tutorial :)
If you have any questions, drop me a line at firstname.lastname@example.org or message me as karen1573 at Renderosity or Rendervisions.