• Concept: I wanted to render a subterranean wine cellar with barrels lining
the walls, a table with a couple of bottles on it, and light streaming down
from a grate in the ceiling.
• Models: I created the cellar myself through a combination of a flat plane and
a cylinder with the bottom half removed. I had to invert the normals on the
cylinder so the inside is the visible surface, and then I textured the ground
with a concrete diffuse image and bump map I found online, and textured the
ceiling with a brick diffuse image and bump map I found online. The barrels,
grate (for the light pattern), table, and wine bottles were all found on
turbosquid.com.
• Technical things of interest:
o Sunlight / Skylight: I have two lights in the scene, a point light above
the grate and an area light slightly below the grate. The point light
acts as my sun, casting the harsh shadows down through the grate
above. The area light, which is just below the grate and sized to the
grate, acts as the sky, casting a softer, more subtle and ambient
lighting onto the scene. I implemented falloff in the area light to mimic
getting farther from the skylight. Attenuation is constant and
immediate and is zero at a distance of 15.
o Dust cloud: To accentuate the sunlight I really wanted to have a
particle cloud in the scene, causing beams of light to fall down
towards the table, floor and barrels. However, I started this fairly late
(oops) and didn’t feel ready to attempt an actual particle scattering
implementation. To cheat my way through it, when I assign the color
for each point I increment by the results of a second algorithm. I step
along the vector from the intersection to the camera, and if the
current location is within a bounding box for the light rays, I send a
ray from the current location to the point light. If no intersections are
found, the point light is visible, and I add a small amount of yellow
color to the color for the point I’m tracing from. I add two degrees of
randomness to reduce artifacting: for each test point along the line I
add a small random delta in the x, y, and z directions, and for each
positive result I insert a small amount of randomness to the amount of
light that get’s added.