This is the final image we will try to achieve.
Please note the following points:
- I wrote this tutorial to explain a friend the basics of caustics.
-This tutorial does not go deeply into physical-lightning considerations.
experimenting and testing are required for photo-realistic results.
- Stay in the RENDER module (keyboard shortcut 3)
Because I'm a cool
guy I've already prepared a scene that you should be able to drag-drop
from the xsi netview :
did it work? I sincerely
hope so :-))
If if did not, you can download it here: caustic_start.zip(48k)
if you render, preview or render region you'll get something like this:
(don't forget to select the good camera!)
so we are going to
assign this cube a glass looking material.
under transparency/reflection tab -> transparency to 0.6
( use CTRL to move all 3 sliders at the same time)
Note: if your picturelooks a bit different it's possibly
due to the fact that XSI merges scenes when importing
so you'd still have default light and ambiance values (delete the def.
lights and set the ambiance to 0)
Ok. Now we are going to
add some "realism" by working with caustics lights.
There are 3 things
to configure before a caustic render can begin.
Please note that the procedure is similar to configuring a global illumination
- First we will configure the light to be a photon
- Secondly, we have to define which surface will transmit, receive (or
both) the photons.
- and finally tell mental ray to
calculate the caustic in the scene.
the spot and click modify>shader: (should be a white spot with intensity
under the Photon tab click the caustic checkbox and set
the following values:
Energy : RGB 0.7
Energy Intensity :
Number of emitted photons Caustic : 2400
(more photons =
longer the render time but accurate results)
the cube and the ground (called cube and cube1 !)
Now modify the common
property called visibility (using the selection button
on the right panel)
and check both checkboxes under the caustic tab.
You can of course optimize performances by choosing which
object transmits or receives or not (!)
here are the values
and i'm too lazy to copy them so please have a look at the following
again note that this is just an introduction... i'll add the comments
on optimizing and adjusting the values later!!
if you render you
should get results like this, no?
Ok so that's it for
now... it's late and i'm going to bed soon.
Just add a refraction index of 1.4 and an area spot and get a picture
like this one.
Some basic things for improving quality are: - increasing the number
of photons and increasing the number of raytracing depth or photon depth
You can also change the values for different results...