A White Plane That Fades Into A White Background
By Neil Blevins
Created On: July 25th 2005

Go here to read this tutorial in Russian.

A common asked question is how to make a white plane that catches the shadows from your objects, but that then fades off as it goes into infinity with a white background. An example of what I'm talking about is seen in my White Orbs image from my gallery...

Lets start with a simple example. Here's a teapot on a white ground plane, and there's a skylight and a spotlight with shadows in Brazil.

Here's the max file that made the image above, max7, brazil rio: rio_whiteplane1.zip (20K)

Now why if the groundplane is white (color value of 1.0) doesn't it appear white and properly fade off into the white background? Because if you add up all the light hitting the plane, the light multiplier value of the skylight and the spotlight is far less than a value of 1.0. So even though the material has a color value of 1.0 (white), it's multiplied by the lighting which is less than 1.0 to give you a final image color value of less than 1.0. And the background color is just that, a color, it recieves no lighting information and so remains pure white while the plane doesn't.

So the first thing you might try is turn the self illumination of the material to 100%. That should make the plane glow pure white right? Well, it does, but it also gets rid of the shadows, since 100% self illuminated objects don't receive light information from the scene.

Here's the max file that made the image above, max7, brazil rio: rio_whiteplane2.zip (20K)

Ok, so that didn't work. I know, lets raise the light level in the scene such that the amount of lighting hitting the ground plane is equal to or greater than 1.0, that way the surface will be fully illuminated and my plane will be white! Well, that does work, but unfortunately the rest of your scene is now blown out. And currently there's no way in max to have a light have a separate multiplier for 2 different objects. And even if it did, the shadow may still be more blown out than you want.

Here's the max file that made the image above, max7, brazil rio: rio_whiteplane3.zip (20K)

So now the answer, or at least the easiest one, assign a Matte/Shadow Material to the ground. A Matte Shadow Material has no shading, so you'll see through to your white background, but it will catch shadows as long as you make sure "Receive Shadows" is checked on. It also has other parameters to let you fiddle with the darkness and color of your shadow.

Here's the max file that made the image above, max7, brazil rio: rio_whiteplane4.zip (20K)

Another possibility is to borrow a technique from real lighting studios. A lighting studio will get large sheets of paper or fabric and drape them on the floor, and then have them curve upwards as they approach the horizon line. This causes a smooth transition from the floor to the background. Here's an example in max:

Here's the max file that made the image above, max7, brazil rio: rio_whiteplane5.zip (20K)

Notice this doesn't fade to a pure white background, but if you place a light or two near the background you can certainly make it white, or maybe the nice gradation you have going on here is visually pleasing and you keep it.

Other things to try to allow your plane to fade off into the background would be...

• place an opacity map on your plane, so close to your objects your plane is fully opaque, and as the plane goes off into the distance it becomes completely transparent, revealing the background (a gradient ramp set to radial would be a good map to use).
• the same thing, but instead of an opacity map, try a self illumination map, 0% self illumination near your objects, 100% in the distance