From BlenderWiki

Baking Radiosity

Radiosity Tool

Description

Radiosity can be used also as a tool for defining vertex colors and lights. This can be very useful if you want to make further tweaks to your models, or use them in the Game Engine. Furthermore, the radiosity modeling allows for adaptive refinement, whereas the radiosity rendering does not! There are few important points to grasp for practical radiosity modeling: Only meshes in Blender are allowed as input for radiosity modeling. This because the process generates vertex colors… and so there must be vertices. It is also important to realize that each face in a mesh becomes a patch, and thus a potential energy emitter and reflector. Typically, large patches send and receive more energy than small ones. It is therefore important to have a well-balanced input model with patches large enough to make a difference! When you add extremely small faces, these will (almost) never receive enough energy to be noticed by the ”progressive refinement” method, which only selects patches with large amounts of unshot energy.

Non-mesh objects Only meshes means that you have to convert curves and surfaces to meshes before starting the radiosity solution!

Collecting Meshes

Description

The first step in the process is to convert the selected meshes to radiosity patches, to participate in the solution.

Options

Radio Tool panel, before meshes collecting.

Radio Tool panel, after meshes collecting.

Collect Meshes

Convert all selected and visible meshes in the current scene to patches. As a result, Collect Meshes is no more highlighted, and a new panel, Calculation, appears. Blender has now entered the Radiosity Modeling mode, and other editing functions are blocked until the newly highlighted button Free Data has been pressed.

After the meshes are collected, they are drawn in one of the three pseudo lighting modes, that clearly differ from the normal drawing. The Radio Tool panel has three buttons controlling this:

Wire, Solid, Gouraud

These control the radiosity modeling draw mode to be used, independently from the indicated draw mode of a 3D window. Wire gives a wire view of the meshes, with the subdivided elements produced during calculations, and colored according to the computed solution. Solid shows all elements as solid flat faces, without blending between neighbor elements’ colors. Gouraud display is only performed after the radiosity process has started – use it to have nice, smooth colored surfaces.

Subdivision limits

Description

Blender offers a few settings to define the minimum and maximum sizes of patches and elements.

Options

Limit Subdivide

With respect to the values PaMax and PaMin, the patches are subdivided. This subdivision is also automatically performed when a GO action has started (Calculation panel).

ElMax, ElMin, PaMax, PaMin

The maximum and minimum size of elements and patches. These limits are used during all radiosity phases. The unit is expressed in 0.0001 of the bounding box size of the entire environment. Hence, with default 500 and 200 maximum and minimum settings, patch size is between 0.05 (1/20^th of the entire model) and 0.02 (1/50^th of the entire model).

ShowLim, Z

These buttons allow you to visualize the patch and element limits. By pressing ShowLim only, you get the limits drawn in the global XY plane. Z only gives limits drawn in the global XZ plane, and with both enabled, in the global YZ plane. The white lines show the patch limits, cyan lines show the element limits.

Adaptive Subdivision

Description

The Calculation panel regroups the last settings before starting the calculations – those controlling the adaptive subdivision of elements and patches.

Options

MaxEl

The maximum allowed number of elements, from 1 to 250 000. Since elements are subdivided automatically in Blender, the amount of used memory and the duration of the solving time can be controlled with this button. As a rule of thumb, 20 000 elements take up 10 Mb memory.

Max Subdiv Shoot

The maximum number of shoot patches that are evaluated for the “adaptive subdivision”, from 1 to 250.

Subdiv Shoot Patch

By shooting energy to the environment, errors can be detected that indicate a need for further subdivision of patches. The subdivision is performed only once each time you call this function. The results are smaller patches and a longer solving time, but a higher realism of the solution. This option will also be automatically performed when the GO action has started.

Subdiv Shoot Element

By shooting energy to the environment, and detecting high energy changes (frequencies) inside a patch, the elements of this patch are selected to be subdivided one extra level. The subdivision is performed only once each time you call this function. The results are smaller elements and a longer solving time and probably more aliasing, but a higher level of detail. This option will also be automatically performed when the GO action has started.

SubSh Patch

The number of times the environment is tested to detect patches that need subdivision.

SubSh Element

The number of times the environment is tested to detect elements that need subdivision.

Computing Radiosity

Description

This is where the radiosity solution is actually computed. You’ll find here the same options as those for the direct radiosity rendering.

Options

The Radio Render panel.

The Calculation panel.

Hemires, Max Iteration, Convergence

The hemicube resolution, maximum number of radiosity iterations, and maximum remaining level of unshot energy. These three settings have already been described in the previous page, and are still active here, with the same meaning.

GO

Start the radiosity simulation. The phases are:

• Limit Subdivide. When patches are too large, they are subdivided.
• Subdiv Shoot Patch. The value of SubSh Patch defines the number of times the Subdiv Shoot Patch function is called. As a result, patches are subdivided.
• Subdiv Shoot Element. The value of SubSh Element defines the number of times the Subdiv Shoot Element function is called. As a result, elements are subdivided.
• Subdivide Elements. When elements are still larger than the minimum size, they are subdivided. Now, the maximum amount of memory is usually allocated.
• Solve. This is the actual “progressive refinement” method. The mouse pointer displays the iteration step, the current total of patches that shot their energy in the environment. This process continues until the unshot energy in the environment is lower than the Convergence value, or when the maximum number of iterations has been reached.
• Convert to faces. The elements are converted to triangles or squares with “anchored” edges, to make sure a pleasant not-discontinue Gouraud display is possible.

This process can be terminated with Esc during any phase.

Editing the solution

Description

Once the radiosity solution has been computed, there are still some actions to take.

Options

The Radio Render panel.

The Calculation panel.

The Radio Tool panel.

The radiosity panels, with post-processing settings highlighted.

Mult, Gamma

These two options from the Radio Render panel control the luminosity and contrast of the result, as described in previous page.

Other post-processing features, specific to radiosity modeling, are found in the Calculation panel:

Element Filter

This option filters elements to remove aliasing artifacts, to smooth shadow boundaries, or to force equalized colors for the RemoveDoubles option.

RemoveDoubles, Lim

When two neighboring elements have a displayed color that differs less than the limit specified in the Lim setting, the elements are joined. The Lim value ranges from 0 (same colors) to 50.

FaceFilter

Elements are converted to faces for display. A FaceFilter forces an extra smoothing in the displayed result, without changing the element values themselves.

Finally, you must “apply” your radiosity modeling to your scene, in the Radio Tool panel:

Add New Meshes

The faces of the current displayed radiosity solution are converted to mesh objects with vertex colors. A new material is added that allows immediate rendering. The input-meshes remain unchanged.

Replace Meshes

As previous, but the input-meshes are removed/deleted.

Free Radio Data

All patches, elements and faces are freed in memory. You must always perform this action after using radiosity to be able to return to normal editing.