# disk2.rib # setting the world coordinate system Display "disk2" "framebuffer" "rgb" Projection "perspective" "fov" 40 Format 320 240 1 Translate 0 0 3 # a transformation WorldBegin Color 1 0 0 # an attribute Disk 0 0.25 360 WorldEnd
The primary 3D coordinate system in RenderMan is the camera coordinate system.
Until the renderer reads
WorldBegin the camera defines the current coordinate system.
From a users point of view, applications such as Maya and Houdini enable a camera(s)
to be moved within a fixed modeling (world) space. However, internally these applications
behave in the same way as RenderMan in the sense that the world is defined after
the characteristics of the camera have been established. Therefore, it is the scene
that is orientated with respect to a fixed, or primary, camera coordinate system.
This tutorial explains what transformations and attributes mean in the RenderMan specification. The
Translate command is one of four transformations.
The others are
The effect of these transformations will be seen in the next couple of examples. For
now we will focus on translations. The effect of the
Translate statement is,
When the renderer reads
WorldBegin a copy of the camera coordinate
system, now moved out in front the camera, becomes the primary or current coordinate
system. It is named the "world" coordinate system.
Transformations are accumulative. For example, these two translations,
Translate 0 0 3 Translate 0 0 3
have exactly the same effect as a single translation ie.
Translate 0 0 6
Color statement sets a RGB value. Attributes are not acculumative ie.
Color 1 0 0 Color 0 0 1
does not specify purple. The second
Color statement makes blue the current color. In
effect, the second statement replaces or hides the first color statement. The RGB
color components must be in the range 0.0 to 1.0. Unlike Maya, geometry in RenderMan
can be colorized without the use of a material.
Opacity is another attribute that can
effect the transparency of an object irrespective of an objects "material" properties.
# disk2.rib # setting the world coordinate system Display "disk2" "framebuffer" "rgb" Projection "perspective" "fov" 40 Format 320 240 1
Translate 0 0 3 # a transformation
Two comments about the scene.
The copy of the coordinate system now becomes the primary, "world", or current coordinate system.
Disk 0 0.25 360
Create a disk at the origin of the "world", 0.25 units in radius and 360 degrees in circumference.
Conclude the description of the 3D scene.
© 2002- Malcolm Kesson. All rights reserved.