Chrome Mapping Example / Tutorial / Walkthrough

This is our background plate (click for full resolution pic). The "chrome sphere" in this case is simply a simple plstic christmas ornament, and the frame is shot w. a Canon MV30i video camera, in a messy garage :) and the shot is actually part of the robot-creation sequence from Kid Wars, my star wars fanfilm.

In this case we use the image as-is, since our CGI will be on top of the sphere, but one could easily have edited together an empty plate where the sphere was not present to use as a background.

Next thing we do is throw in some simple geometry, in this case a chamfered box (for the background object), a teapot primitive (gotta love those, huh :-D ) and finally a sphere and a capsule.

You can probably do a much better model yourself.

Before we move on to the actual Chrome Mapping, lets make our base image somewhat prettier by modifying the material for the chamfer box. Go into the material editor, pick a slot, and click the "Standard" button and instead choose "Matte/Shadow" material.

In the dialog that pops up:

  • Turn off "Opaque Alpha"
  • Turn on "Receive Shadows"
  • Turn on "Affect Alpha"
  • Set a nice "Shadow Brightness", 0.35 worked in our case
Also, right click the box and select "Properties" and uncheck the box for "Visible in Reflections". If we don't do this, the dumb ratytracer (used later) will try to reflect the matte objects!!!

Then we need a material for our "Chrome Mapping" experiments. Take a new slot, turn the color to all black. Give it a wee bit of specular (not much, the chrome map will contain most we need) and slap it to our objects.

The result will look something like the image below:

Black objects, but with a shadow. So far, so good...

Now the fun bit

In your material, scroll down to the "Maps" rollout, and click the "Reflection" map entry. In the dialog that pops up, choose "Chrome Map".

Clicket yee "Chrome Map"

But the Chrome Map is no good in itself... it is just a magical transformation matrix provider. You still need something (a photo of a ball) to actually "relect". So in the "Chrome Map" rollout that just appeared, click the "None" button, and pick "Bitmap":

Select a Bitmap to reflect

Now, in the Bitmap file dialog select our background plate again! (Yes, we are lazy, we use the same map). But the Chrome Map must be an image of a sphere, nothing more, nothing less. To do that, we use the "Crop" option in the Bitmap:

In the "Bitmap Parameters" rollout:

  • Check the "Apply" button
  • Make sure "Crop" is selected
  • Click "View Image"
  • Modify the handles so they precicely enclose the sphere

When you have done this, you SHOULD see, in the material editor, that the "demo sphere" bears a remarkable, uncanny similarity to the sphere from the image! In fact, it should be borderline identical, safe for the slight extra specular highlight! If you now render the image we have so far, you will get something like this:

Not too shabby, huh? You see the reflection of the hand in the teapot!

Now the poor quality of the original photo starts to rear it's ugly head (The better photo you have, the merrier, as they say) but we can try to do something about this. Go into "Coordinates" rollout on the Bitmap and change the blurriness:

A little blur, and we have a brushed metal teapot

There is still some more steps towards "full" realism. As all reflection-maps you do not get any self-reflection on this object. Lets do something about that. First, turn the blur back down so it's only slightly blurry. Then go up to the "Chrome Map" level by clicking the little "Up" arrow, and then click on the button that reads "Chrome Map", and select "RayTrace" instead:

Lets RayTrace instead...

But now a deadly important dialog pops up: What to do with the Chrome map? You must select "Keep old map as sub-map". This will keep the Chrome Map as the map that is used when the "Ray Trace" function can't find any objects to trace!

If you render the image again, you will get something like the below:

Self reflecting teapot (the spout is reflected in the body)
but still reflecting the environment - nifty!

We are getting really close to the ultimate teapot, all we need to do is to adjust a couple of things. First, the original image is grainy. Go into "Render Effects" and hit the "Add" button and choose the "Film Grain". Set it to "Ignore Background" and to a fairly light setting to match the grain in the original picture.

And as a final touch, note that the image itself isn't entirely clear. To duplicate that, one way is to go into the "Rendering" dialog itself, and play with the filter settings. Here we use an "Area" filter of 2.5 pixels:

Area filter, 2.5 pixels, to match backgrounds blurriness voila?

A pretty damned OK teapot, in less than 5 minutes

You can get the MAX file for this scene here, and it needs this map.

Now for the good part... everything we done so far is technically doable without help of other tools than the Chrome Mapping plugin, but with varying degrees of extra work needed to convert the "image of a sphere" into something usable as a reflection map. But with the "Chrome Mapping" plugin, its a one step process. And this allows us to use video as our map. If you videotape your chrome sphere while things around it move, these reflections will look very accurate when mapped onto an object using same video to composit with. For an example of this, watch "Kid Wars", the robot building sequence.

Of course nothing forces you to do everything bright and shiny. You can use this reflection map as any other reflection map, only for spice e.t.c. Also, blurring it A LOT (way beyond the level we did on the "brushed metal teapot") actually makes it an interesting base for lighting. (The robot building sequence in "Kid Wars" HAS no lighting at all, beyond chrome mapping, raytracing, and "light/shadow" falloff maps).

Beyond this, only your imagination is the limit:

Your imagination is the limit. Mine didn't stretch further than this...

Continue to example page #2 ==>
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