VARIABLES

This is the direction of the ray from the camera to
the current intersection point on the surface,
the normalized difference between point and org.

This is the interpolated normal of the point of intersection.

This is the geometric normal of the hit primitive.

This is the origin of the ray. 
In material shaders this is the camera postion.
In light shaders this is the light postion.

This is the point of intersection with the surface.

This function returns the reflection direction based on the
dir, normal and normal_geom state variables.

This function returns the refraction direction based on the
interior and exterior indices of refraction and on the dir,
normal and normal_geom state variables.

The state->type value will be the type of ray cast.
This function return miTRUE if TYPE matches the current state->type.
miRAY_EYE rays are primary rays. 
miRAY_TRANSPARENT rays are cast to determine transparency.
miRAY_REFLECT rays are cast to determine reflections. 
miRAY_REFRACT rays are cast to determine refractions.
miRAY_SHADOW rays are cast by lights to determine shadows. 
miRAY_LIGHT rays are cast when lights are evaluated. 
miRAY_ENVIRNOMENT rays are cast to sample an environment map. 
miRAY_NONE is none of the above or all other rays.

This is the acceleration data, used for motion blur.

This is the three barycentric coordinates of the intersection
in the hit primitive.  The fourth value will be for patches.
Barycentric coordinates are the weight of each vectex.
The sum of all barycentric coordinates is one.

This is the length of the ray from its origin, state->org,
to the current intersection point on the surface, state->point.  
If there is no intersection, the length is infinite, 
a zero or a negative is returned.

This is the dotproduct of the geometric normal and the ray.

This is the index of refraction for the medium, the ray is traveling though.

This integer indentifies the hit primitive. 

This is the time of the ray in the shutter interval,
sampled in the range from 0 to the shutter time.
If motion blurring is off, time returns a zero.

This is the current level in the refraction tree.  Primary rays 
are at level 0.  The last level is the refraction_depth minus one.  
A shader may increment, decrement or reset this level to circumvent 
the restrictions imposed by the trace depth state variable.

This is the current level in the refraction tree.  Primary rays 
are at level 0.  The last level is the refraction_depth minus one.  
A shader may increment, decrement or reset this level to circumvent 
the restrictions imposed by the trace depth state variable.

This is the tolerance at which the intersection of the shadow
ray with the primitive is ignored.  This prevents self-shadowing errors.

Is contour rendering on?
miTRUE  = yes, use simplified calucalations.
miFALSE = no,  render images.

Was this hit made using the scanline rendering algorithm?
miTRUE  = yes, but motion blur cannot be used.
miFALSE = no,  pure ray tracing is being used.  

This is the aperture of the camera,
the width of the viewing plane in camera space.

This is the aspect ratio of the camera,
the y_resolution divided by the x_resolution.

These are the hither and yon clipping planes in camera space.

This is the focal length of the camera,
the distance from the camera origin to the viewing plane.

Is the render orthographic or in perspective?
TRUE = orthographic.  
FALSE = perspective; this is the default.

This are the X and Y raster values.

These are the x and y resolutions of the image in pixels.

These are the corners of the window into the image to be rendered.
If they equal or exceed the resolution, the window is set to the 
resolution.

This is the current frame number.

This box makes it possible to generate start/end/current frame values.
0 is returned if current frame = start frame
1 is returned if current frame = end frame.

This is the frame time in seconds.

This does a 2D texture lookup for displacement.
TAG  is the tag for the Texture Shader.
MODE is the texture mapping method.
COMP controls which component of the map to use, alpha or intensity.
MAG  is the magnitude of the displacement.

This shader assumes the entire scene is enclosed in a mapped sphere.
TAG   is the tag for the Texture Shader.
ROT   is the rotation about the world Y axis.
MASK  controls the blending method.
BLEND controls the amount of blending.

This implements the Softimage material shader.
TAG   is the tag for the texture shader.
SPACE selects the mapping space.
MASK  selects the type of masking for color maps.
COMP  selects whether scalar maps come from alpha or intensity.
METH  selects the type of mapping projection.
BLEND is the amount of blending globally.
AMB   is the amount of blending with the ambient surface color.
DIFF  is the amount of blending with the diffuse surface color.
SPEC  is the amount of blending with the specular highlight color.
TRNSP is the amount of blending with the transmitted color.
RFL   is the amount of blending with the reflection color.
BUMP  is the magnitude of normal perturbation.
UUNIT is the amount of detail in the U direction.
VUNIT is the amount of detail in the V direction.
BW    is boolean: miFALSE = use color; miTRUE = use B&W. 

This is the array of texture coordinates mapped to the surface.

These are the parametric values of the surface at P;
which have been scaled and/or offset.

This is the list of bump map basis X and Y perturbation vectors.

This is the matrix which represents the object transformation.

This is the matrix which represents the inverse object transformation.

This is the matrix which represents the world transformation.

This is the matrix which represents the inverse world transformation.

This is the matrix which represents the raster space transformation.

This is the matrix which represents the inverse raster space transformation.

This is the matrix which represents the screen transformation.

This is the matrix which represents the inverse screen transformation.

This is the X and Y resolution of the frame.

This returns the state->frame_label pointer to the labels frame buffer.
This is a frame buffer containing all the object labels for the image.

This returns the state->frame_n pointer to the normals frame buffer.
This is a frame buffer containing all the surface normals for the image.

This returns the state->frame_rgba pointer to the rgba frame buffer.

This returns the state->frame_z pointer to the z depth frame buffer.

This is the matrix which represents the camera to world transformation.

This is the matrix which represents the world to camera transformation.

Motion blur turned on? miTRUE = yes.  miFALSE = no.

Use the scanline rendering algorithm?
miTRUE  = yes, but motion blur will not be enabled,
and lens shaders cannot change the ray origin and direction.
miFALSE = no,  pure ray tracing will be used.  
This may (WILL) slow down the rendering process.

Is shadow casting on?
miTRUE = yes, shadows are cast.  
miFALSE = no, shadows are not rendered.

Call the shadow shader in order, closest first?
miTRUE  = yes, shadows closest to the light source
will be rendered first.
miFALSE = no,  shadows will be rendered in random order.  

Do secondary ray tracing?
miTRUE  = yes, reflection and refraction are evaluated.  
miFALSE = no,  only eye and transparency rays are evaluated,
and no shadow will be computed regardless of the shadow flag.

This specifies the ray tracing alogrithm.
There are two types: Ray Classification, better.
Space Subdivision, sometimes faster.
The default is scanline if ray tracing is not requested.

This specifies which face of the triangle is used in 
rendering calculations.  Single faces can speed up the render.
There are three choices: just the front face,
only the back face,
or both faces.

This turns field rendering on. This is only available
when the scanline rendering alogrithm is used.
There are three choices: Off, the default,
Even fields only,
Odd fields only.

This specifies the type of filter for sampling.
There are three types:  Box, the default.
Triangle, the cheapest.
Gauss, the most exspensive.

This specifies the supersampling algorithm.
There are three modes:  Recursive, the default.
Constant, same number of samples per pixels.
Adaptive, the cheapest.

This specifies the maximun number of recursive reflections.
A reflection ray will only be cast if this limit is not exceeded.
If zero no secondary reflection ray will be cast, this is the default.

This specifies the maximun number of recursive refractions.
A refraction ray will only be cast if this limit is not exceeded.
If zero no secondary refraction or transparency rays will be cast.

This specifies the maximun number of segments allowed 
in the ray tree when it is followed through the scene.
Any combination of reflection and refraction rays may
be used until this limit is reached.

This specifies the shutter speed for motion blur.

This is a user defined constant of any data type.
The output and input should be of the same data type.

This is the color or value returned to the Renderer.