Day 11

Okay so now I am back on track with RenderMan. Starting to get into more complicated things(still spheres though, love them). I tried out a few camera settings and various renderMan light shaders that I learned about on Saturday.

This is the general setup I am using for the files today:

RenderMan Cameras

The field of view(fov). RenderMan, by default, uses a 90 degree fov, which results in a stretching artifact at the edges. This is an image with a 30 degree fov, compared with one with a 90 degree image.

fov 30 and fov 90

As you can see the image on the left is not stretched at the edges.

Pixel Samples. The pixel samples determine the amount of points that are calculated per pixel. A higher number gives a sharper image and a lower number gives more artifacts. Here are some tests I did with PixelSamples values 1 1, 2 2 and 4 4.

Pixel samples 1 1

Pixel samples 2 2

Pixel samples 4 4

Exposure settings. I also tried out various exposure settings for the camera, gamma correcting the images. In the output below you can see that the image on the right has no gamma correction whereas the image on the right is gamma corrected and looks blown out.

RenderMan Light Shaders


I started off with the simple point light shader. As expected it illuminates the facing surface. As an input it takes a "from" position and an intensity. The intensity needs to be set pretty high as the falloff is quadratic by default. Also, we can set which object receives light on a per object basis. In the output below the sphere on the left receives illumination from a point light source and the one on the right doesn't.

Point light shader with per object illumination set

Then I experimented with the distant light shader, that basically works like a normal Maya directional light. It takes a "to" position and an intensity.

Distant light shader

Spot Light shader is one of the more complex one in renderMan as it has a lot of attributes. In the three outputs below I have set the coneDeltaAngle differently, giving me a different penumbra. This essentially sets the falloff from the brightest central part of the light to the outer edge, giving softer edges, if desired.

coneDeltaAngle = 0.0
giving a hard edge

coneDeltaAngle = 0.1
giving a softer edge

coneDeltaAngle = 0.25
giving a significantly softer edge

Ambient light shader just flat shades the sphere (as expected)

Ambient Light Shader

Compound Light. Here I used a spotlight shader with a large cone angle 0.45 and a large delta angle and an ambient light shader with low intensity (0.2) to give a fill light to fake GI. Its not much, but I am pretty pleased with the result for now.

Thats all from renderMan today> Tomorrow I will try to import a few more complex objects and work with materials other than the simple plastic used here.