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Avenue 4.5 and Arena 5

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Projection Mapping

As far as the output is concerned, projection mapping is usually a lot more guesstimating and eyeballing than working with LED screens. Even then, having a good input map is a great time saver.

Let's take the following example of a structure consisting of 8 cubes. Even if you don't know the exact layout of the objects on the night itself, you know it's going to be something close to this.

You can already start working on this before you even arrive at the venue.

To have some creative options on this stage design, you might want to play some content over the entire structure, and other content only in a single cube or in a combination of cubes, Most people will use Layer to Slice routing for this. This is a great technique, but it severely limits your options. You will lose all blend modes and composition effects. More importantly, you will have to map each cube again for each layer you want to play in it. That's a lot of work and mapping is enough work as it is.

Instead, we'll use some clever layer settings and an input map to make this much simpler.

Creating the input map

First thing is to create an input map based on this shape. We start by creating the exact same cube shape, in the Advanced Output using slices.

First we have to figure out how big to make our composition. If we take a regular HD signal (1920×1080 pixels) as our starting point, we will need 8 slices of 360×360 pixels. We know this, because the object is 3 cubes high and 1080 / 3 = 360.

This means that our Resolume composition will be 1080×1080, because cubes are always square. So set the composition size to 1080×1080.

Open the Advanced Output and make sure you are working on the Input Selection stage. Let me repeat this, because I don't think you heard me. Make sure you are working on the Input Selection stage. We're not interested in the Output Transformation at this point, only in choosing which parts of our composition to use.

After you've created the first slice, place it exactly in the bottom center of the Input Selection stage. Now create copies and place them around the stage, in the same positions as the actual cubes. This will go really quickly, because you can alt-drag to copy the slice, and then the copy wil snap to the original and the composition edges.

Bam. Your input map is done.


Setting up the Composition

Now in the composition, we'll make our first layer our Fullscreen layer. This is easy, because the input map already takes the correct input from the comp. We'll lose some of our 1920×1080 content on the sides, but we're keeping the aspect ratio intact so our circles stay circles.

Moving right along.

Layer 2 will be our Everywhere layer. Using a Tile effect with the TileX and TileY parameters exactly at 0.15, we'll have 9 copies of our content in exactly the right place. Bam, Everywhere layer done.

If you're not getting 9 exact squares, make sure you've flipped the render order of the Transform and the Effects.

We'll duplicate this layer, and add some Crop effects to show or hide the content on specific cubes. You can create as many duplicate layers as you want content on specific cubes.

On the last layer we'll add some animated Lines from the Sources tab. Using the LoRez effect with its Pixelation parameter at almost maximum, we'll have 9 blocks of white turning on and off. We can use this as a mask or as some stroby bump content.


Aligning the output

When you're at the venue and connected to the projector, go to the Output Transformation stage, lasso all the slices and right click them. Choose Match Input Shape and all the slices will pop to the place they have on the input stage.

Now move and scale the cube grid roughly into position. Where necessary, drag the individual corner points to align exactly with the projection. After a little work, the projected input map should line up exactly with the actual object.


Custom content

Because you have created an accurate input map, you can easily mix custom content with your regular VJ content. As long as you make the cubes in your content exactly 360×360 and the clip itself exactly 1080×1080, it will line up perfectly with your other content.

VJFit has an excellent tutorial on how to make custom content in Cinema 4D for this setup.

An added advantage is that, should you do this show in a different location, you can just re-use the same animations and input map. All you need is adjust the output to the new projector location and you're good to go for show!

Here is a zip file containing both the Resolume comp file as well as the Advanced Output preset that we've discussed here.


Non-geometric objects

When working with objects that are not geometric, you have to rely on the content to make your input map. For instance, to map on an inflatable skull like this, you will first have to make the content in Cinema 4D based on the measurements of the actual skull.

Then you divide the skull into several poly slices, one for each major part of the object. You can go with a slice for the forehead, one for each eye, jaws, nose, left cheek and right cheek, upper teeth, lower teeth and chin. Of course, you can create more or less poly slices, the more or less accurate you want to be. You can go as far as creating a poly slice for each tooth.

Then you position and scale each poly slice roughly in the projection and fine tune its points to align perfectly.

Tip! On any projection mapping job, take plenty of breaks, bring a thermos of tea and some good music. A masseuse is optional.


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