RadVis Help

The following are brief notes on how to use the radvis radiosity visualisation program. Hopefully at some stage they will be replaced by highly detailed notes with lots of demonstration images. In the meantime, if you have any questions/suggestions, please email ajw+rv@cs.cmu.edu.

Sections:



Scene Pane

This shows the current scene. The scene can be manipulated by clicking on it with the mouse as follows:

When using the right-mouse to select a patch, the initial click will select one of the leaf nodes in the mesh. For the hierarchical meshes used in wavelet radiosity and progressive radiosity with substructuring, elements at higher levels in the mesh can be selected by keeping the mouse down, and dragging away from the initial click point. The futher you drag, the higher up in the hierarchy will the patch be selected, until eventually the root patch is reached.

Matrix Pane

Shows the matrix corresponding to the current scene and radiosity method.


Status Lines

These are located below the scene pane. The top line shows what the current radiosity method is doing while it runs, and the bottom two display various scene statistics.

Options Panel


The options panel contains the following three popup menus:

Radiosity Method
This selects the radiosity method to use. The methods are as follows:
Overrelaxation
Matrix radiosity, with the matrix equation solved by the successive overrelaxation technique.
Conjugate-Gradient
Matrix radiosity, with the matrix solved by the conjugate gradient technique.
Progressive
Progressive radiosity: radiosity is shot from light sources, rather than gathered into each patch in turn.
Prog./Substructuring
Progressive radiosity with a bi-level mesh. Radiosity is shot using a relatively coarse mesh, and received over a finer one. The receiving mesh can be subdivided in areas that have a high radiosity gradient. (E.g., shadow boundaries.)
Wavelet
Wavelet radiosity, a la Gortler et. al. In this case the mesh is multi-level, and different types of basis functions can be used over the mesh. If the Haar (constant) basis is used, this reduces to Hierarchical radiosity.
Analytical
For scenes where there is no inter-reflection(!), this will find an analytical solution to the radiosity equation.
Basis
Selects the type of basis used for wavelet radiosity. The currently supported bases are Haar, the flatlets F2 and F3, and the multiwavelets M2 and M3.
Scene
This popup menu either selects one of the built-in scenes to use, or allows you to load an external scene file.

Sliders

Patch Subdivisions
Controls the density of the mesh for matrix/progressive radiosity.
Alpha
For the overrelaxation method, this controls the overrelaxation amount. (1.0 = standard gauss-seidel iteration.)
Element Subdivisions
Controls the density of the element mesh in the progressive + substructuring method. For this method, Patch Subdivisions controls the density of the mesh used for shooting radiosity, and the Element Subdivisions setting controls the density of the mesh used for receiving that radiosity.
Termination Error
The error level at which to terminate the simulation.
Refinement Level
For the progressive + substructuring method this determines the threshold at which to subdivide a element of the mesh, and for the wavelet methods, it sets a limit on the form-factor error. (The smaller the number, the more the mesh is subdivided to reduce this error.)
Patch Size Limit
Patches will not be subdivided below this limit.

Control Panel

Go
Start the radiosity simulation.
Pause
Pause it!
Step
(While paused.) Perform another step of the radiosity simulation, and then pause again.
Reset
Prepare for another radiosity render.
Avars
Brings up the avars window, which can be used to manipulate the scene.
Exit
leave the visualiser.

Rendering Options

Wireframe
Draw the scene in wireframe mode.
Gouraud Shading
Gouraud-shade the mesh.
Function View
Offset each mesh element according to how bright it is. (Makes it easier to see the distribution of radiosity.)
Patch's View
When this is on and wavelet radiosity is selected, the scene is displayed relative to the currently- selected patch. Patches that contribute radiosity directly to that patch are coloured normally; patches that contribute radiosity to its children are drawn wireframe, and patches that contribute radiosity to its ancestors are drawn outlined in red.

Animate
Animate the radiosity simulation by highlighting relevant patches.
Show Rays
Display all rays traced for visibility determination.
Show Links
Show which patches are being linked together. (Wavelet radiosity only.)

Graded Mesh
For the hierarchical meshes, ensure that any adjoining mesh elements differ by at most one level in the quadtree.
Anchored Mesh
Use 'anchoring' to avoid problems with T-vertices, such as discontinuities in shading. This requires that the mesh is graded.

Progressive options

Add Ambient
Add in the ambient correction term.
Shot Display
Show the amount of unshot radiosity in the scene.

Wavelet options

BF Weighting
Concentrates mesh refinement in those areas where significant radiosity transfer is taking place.
Multigrid
Intermixes the refinement and solution steps of the wavelet radiosity method. If this is not selected, refinement is done first, and solution afterwards.

Plot Panel

Plot Factors
If a receiving and a source patch are selected, this will produce a 3D plot of the form factor distribution over the receiving patch.
Plot Radiosity
Produces a 3D plot of the radiosity over the selected patch.
Resolution
Controls the number of samples used to produce the above plots.

Misc

Dump Picture
Saves a picture of the scene pane into the file main.tiff.
Dump EPS
Outputs an EPS line drawing of the current mesh.
Dump Camera
Outputs current camera parameters.
Draw Matrix
The matrix display is only drawn when this is on. When the number of elements in the simulation gets large, displaying the matrix can take some time, and it's often useful to turn it off temporarily.
Jump
Adjust the camera so we see the scene from the point of view of the currently-selected patch.

Avars...
Brings up the Avars window
Form Factors...
Brings up the Form Factors window

Avars Window

This shows a list of the avars embedded in the scene, and a slider for adjusting them. Avars can only be changed when a radiosity method isn't running. Depending on the scene, avars can be used to vary the emissivity or reflectivity of certain objects, or their location or orientation.

Form Factor Window


Quadrature Method
Selects among various (somewhat obscure) variations of form-factor calculation. 'None' uses point-to-point form factors, 'PF switch' uses the area-to-point form factor as a correction near singularities, and the remaining options select various combinations of area-to-point samples.
dF Error
Threshold dictating when to switch to the area-to-point approximation when using the 'PF switch' method.
Visibility
The type of visibility estimation to use: no rays, one ray between each pair of patches, sixteen from the centre of the receiver and distributed evenly over the source, and sixteen distributed evenly over both source and receiver.
Vis. In Quadrature
If this is on, visibility is sampled within the quadrature method for higher order wavelets, rather than using the fractional visibility to scale the results of quadrature.
Recalc Jitter
If this is on, a different jitter pattern is used each time the visibility between two patches is estimated.

Plot Window

Add
Add the radiosity over the currently selected patch to this plot.
Subtract
Subtract the radiosity over the currently selected patch from this plot. (This can be used for comparisons.)
Dump Data...
Save the plot data to a text file.
Dump Image...
Save the current picture of the plot as a TIFF file.

ajw, ph, July 15, 1997