Starting Point
Open up Pixels3D and set up our first test. Select the camera and open up Object Info ( CMD-I ) and set the position of the camera to 0.0, 0.0, -35.0 ( x,y,z ). Next, move the Light to a good location on the left or right of the camera.

Create a Mesh
First choose Shapes>Mesh and hit OK. In Object Info ( CMD-I ) change the rot of x to 90.0 and the park it. Next, do a Controls>Scale to size the mesh taking most of the camera's view in the perpestive window.

Apply our First Relfective Surface
Let's open up ShaderMaker ( CMD-W ) and apply a reflective surface shader to our mesh. Use the settings on the left. Remember to set the Raytracer node's colour to black.

Duplicate our Mesh
With our Mesh still selected, CMD-D to duplicate it and move it on the Z plane to a distance near the camera as pictured to the left.

Apply a new Reflective Shader
Back to ShaderMaker, lets create a new shader by clicking on an empty slot. Use the setting as pictured to the left. Notice we set out Opacity, Diffuse, and Ambience to 0.0. This is so we can reflect back our first mesh onto itself without this mesh being reflected back.

Set Up the Recursions
Choose File Menu>Render Setup ( CMD-U ) to open up the renders setup dialog. You should see a checkbox labled Raytracing, check it if it's not already. Below it is an editfield for us to enter an integer value.

About Recursions
Recursions are how may times an object using raytraced surfaces, will be reflected onto itself. So a value of 1 means it will reflect any rays only once, 8 times means it will reflect its rays 8 times.

Recursions Applied
Create any shape, such as a vase, and add a gold shader to it ( use my gold shader from last tutorial and set the refraction to 0.0 ). Move and scale the object to set it near the botom right corner of our first mesh and do a quick render. We can now clearly see our gold object being reflected 3 times in the first mesh.

These are the basics of using recursions in our scene. Now lets try something a little more complicated...

Start
Download this scene file, and open it in Pixels|3D.

Testing Scene
Ok so we obviously can see the differences and power between reflections and usage of recursions. I put together this scene to show a cool way recursions can give your scene some added "magic".

There are 6 objects in the scene using 5 different shaders, all included with the download - a cone, cube, 2 spheres, and 2 meshes. We will need to concentrate on the 2 spheres and one of the mesh's that will be using raytracing.

Rendering without Recursions
Most 3D doesn't utilize raytracing to its full potential. Here, I set the raytracing's recursions to 0, and rendered it out. It still reflects scene objects onto the 3 objects and notice, the objects are not reflecting there own reflections back to one another. Look closely at the water where the bubbles are being reflected upon.

Blownout
Here's an example of how nice recursions can be, as opposed to just raising the reflection values on the 3 objects. On the left is what happens when you try to set the shader's reflections of each object to a value of 1.0, 3 times greater than normal. I circled the ugly areas that are totally blownout in colour and distract the viewer from the entire image.

Ok, so how do you know when your reflection values are not going overboard? Make a test scene with 4 objects spread out; one reflective ( black diffuse colour ), and the others red, green, and blue respectively. Match the colours of those objects against their reflections onto the reflective object, they should be a near exact match.

One Last Problem
Reflections aren't perfect in every way when calculated by a machine, but sometimes we can get them near perfect by being imperfect. The problem with this scene is the reflections of our Candycane shader. If you notice the reflections tend to blur out or overrun the transparent sections of these 2 objects. So, simply lowering the reflection value of the water doesn't help. The only solution here is to use a less "strict" shader unlike stripes.

Have fun!