Relevant to Blender v2.31
Let's assume you have a scene ready, and that you want to render it with the Radiosity Rendering. The first thing to grasp when doing Radiosity is that no Lamps are necessary, but some meshes with an Emit material property greater than zero are required, since these will be the light sources.
You can build the test scene shown in Figure 18.1, “Radiosity example”, it is rather easy. Just make a big cube for the room, give different materials to the side walls, add a cube and a stretched cube within it, and add a plane with a non-zero Emit value next to the roof, to simulate the area light (Figure 18.2, “Set-up for Radiosity test.”).
You assign Materials as usual to the input models. The RGB value of the Material defines the Patch colour. The 'Emit' value of a Material defines if a Patch is loaded with energy at the start of the Radiosity simulation. The 'Emit' value is multiplied with the area of a Patch to calculate the initial amount of unshot energy.
Check the number of 'emitters' on Blender console! If this is zero nothing interesting can happen. You need at least one emitting patch to have light and hence a solution.
When assigning materials be sure that all of them have the
Radio toggle on to enable the
Panel of the Material subcontext buttons (Figure 18.3, “Radiosity enabled material.”).
Please note that the light emission is governed by the direction of the normals of a mesh, so the light emitting plane should have a downward pointing normal and the outer cube (the room) should have the normals pointing inside, (flip them!).
Switch to the Radiosity
sub-context of the Shading Context. The Panels, shown in
Figure 18.4, “Radiosity buttons for radiosity rendering.”, are two:
which governs Radiosity when used as a rendering tool (present case) and
Radio Tool, which governs Radiosity as a modelling tool (next section).
The buttons define:
Hemires: - The hemicube
color-coded images used to find the Elements that are visible from a
'shoot Patch', and thus receive energy. Hemicubes are not stored,
but are recalculated each time for every Patch that shoots energy.
The 'Hemires' value determines the Radiosity quality and adds
significantly to the solving time.
Max Iterations: - The maximum number
of Radiosity iterations. If set to zero Radiosity will go on
until the convergence criterion is met. You are strongly advised
to set this to some non-zero number, usually greater than 100.
Gamma: - The
colourspace of the Radiosity solution is far more detailed than
can be expressed with simple 24 bit RGB values. When Elements
are converted to faces, their energy values are converted to
an RGB colour using the
Gamma values. With the
value you can multiply the energy value, with
Gamma you can change the contrast of the energy
When the amount of unshot energy
in an environment is lower than this value, the Radiosity solving
stops. The initial unshot energy in an environment is multiplied
by the area of the Patches. During each iteration, some of the
energy is absorbed, or disappears when the environment is not a
closed volume. In Blender's standard coordinate system a typical
emitter (as in the example files) has a relatively small area. The
convergence value is divided by a factor of 1000 before testing
for that reason.
Max Iterations: to 100 and turn
to the Scene Context and Render Sub-context (F10).
Radio Tog Button
(Figure 18.5, “Enabling Radiosity in the Rendering Buttons.”) in the
Panel and set it 'on' to enable Radiosity, then Render! (F12).
The rendering will take more time than usual, in the console you will notice a counter going up. The result will be quite poor (Figure 18.6, “Radiosity rendering for coarse meshes (left) and fine meshes (right).”, left) because the automatic radiosity render does not do adaptive refinement!
Select all meshes, one after the other, and in EditMode
subdivide them at least three times. The room,
which is much bigger than the other meshes, you can even
subdivide four times. Set the
Max Iterations a bit higher, 300 or more.
Try Rendering again (F12).
This time the rendering will take even longer but
the results will be much nicer, with soft shadows
and colour leakage
(Figure 18.6, “Radiosity rendering for coarse meshes (left) and
fine meshes (right).”, right).
In the Radiosity Rendering Blender acts as for a normal rendering, this means that textures, Curves, Surfaces and even Dupliframed Objects are handled correctly.