from the author:
This article was written with 3ds max 5 in mind. It should be
noted that later versions of 3ds max contain the ability render
caustics due to the inclusion of the Mental Ray renderer.
at the base package, it’s easy to see why people go along
the third-party plugin route when looking to produce realistic caustics.
Nine out of ten times, it’s just a simple case of settings
a couple of values and clicking render – not much skill is
required and effective results can be achieved. Although these look
good, normally render times suffer as a result; sometimes reaching
several minutes to even hours.
we had to be content with faking these caustic effects using volumetric
lights (for volumetric caustics – caustic effects in fog)
and / or projector maps of the object’s specular info from
the key light source assigned to a duplicate light to cast a bright
projected light only onto the relevant surface(s).
3ds max 5, the introduction of Light Tracer and Radiosity advanced
lighting systems changes the game slightly. Reflective caustics,
such as from contoured metal surfaces or water can be produced,
but refracted caustics still have to be faked. So what has changed?
Light Tracer can bounce light off surfaces and also allows for tinting
of this light to simulate radiosity. By increasing the amount of
specularity in the object’s material, we can increase the
intensity of the bounced light. With a curved surface for example,
this light can form at a focal point, and as light is additive a
more intense point of light is visible.
with a standard Blinn shader setup, our caustic bounced light is
blurred and not focused. The way around this is to use an Anisotropic
shader as this focuses the bounced highlight. Even though this can
produce an effective caustic, getting the caustic effect right means
sacrificing the designed (normal) specular settings, which can make
the material appear different from what we want. To solve this problem,
use a Multi-Layer shader as this incorporates two different specular
highlights. One highlight can be designed as normal, and the second
set to a small intense highlight with anisotropy. Both should be
tinted as necessary. When rendered, 9/10 times the first (larger)
highlight will occlude or white-out the intense highlight and the
material will appear as required, and the caustic effect will now
be properly generated and displayed correctly.
effective results, we can use raytraced reflections if desired,
and although this adds to the render time it results in a convincing
the ca_caustics_start.max file included on the cover cd. This
is our basic scene for which we will light and create the material
to generate the caustic effect. In the top Viewport, create
a spotlight. In the left Viewport, amend it’s position
so it’s situated above the rings. Turn shadows on and
set to Ray Traced. Check on Overshoot in the Spotlight Parameters.
the ground plane and open the Material Editor. Assign the first
material to the plane. Label the second material “Gold
Ring” and assign it to all the rings. Change the shader
from Blinn to Multi-Layer. Take the Diffuse Level to 0. Set
the First Specular Layer colour to RGB 218,195,166 , Level to
500, Glossiness to 70 and Anisotropy to 75. Copy the first specular
colour swatch to the second, set the second’s Level to
150 and Glossiness to 20
material’s Reflection slot, add a Raytrace map. As we
haven’t got much of an environment to reflect in our scene,
we’ll add an extra one with our materials so not only
does it reflect the object, but an environment map also. Add
a bitmap map to the Raytrace map’s Background slot and
load in Lakerem2.jpg which comes with 3ds max 5 in it’s
maps\Reflection folder. Set to Spherical Environment mapping
and set the Blur offset to 0.05.
Light Tracer in the Advanced Lighting window. Leave all settings
as default for the time being, apart from setting the Bounces
to 1. Render the scene. We should now notice the caustic effect
caused by the light being bounced and focused. Increasing the
Light Tracer Rays/Sample setting will sharpen this up at the
expense of render times. You may also want to tweak the sharpness
of the anisotropic highlight in the Material Editor to refine
Arts magazine, Issue 83, May 2003.
Draper, May 2003. Reproduction without permission prohibited.