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>Blender Documentation Volume I - User Guide: Last modified April 29 2004 S68</TH
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>Radiosity</TD
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><H1
CLASS="section"
><A
NAME="radiosity_quickstart"
></A
>Radiosity Rendering</H1
><P
>&#13;		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 <I
CLASS="emphasis"
>no Lamps 
		are 
		necessary</I
>, but some meshes with Emit material property
		greater than zero are, since these will be the light sources.
	</P
><P
>&#13;		You can build the test scene shown in 
		, 
		it is	rather easy, just make a big cube, the room, give different 
		materials to the side walls, add a cube and a stretched cube within 
		and add a plane with an non-zero Emit value next to the roof, 
		to simulate the area light (<A
HREF="x8197.html#BSG.RAD.F.S68.201"
>Figure 2</A
>). 

	</P
><P
>       
		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. 
	</P
><DIV
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><TABLE
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><B
>Emitting faces</B
></TH
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><TR
><TD
>&nbsp;</TD
><TD
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><P
>&#13;		Check the number of "emittors" on Blender console!
            If this is zero nothing interesting can happen.
		You need at least 1 emitting patch to have light and hence a solution.
		</P
></TD
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></DIV
><DIV
CLASS="figure"
><A
NAME="BSG.RAD.F.S68.201"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartR/radiosity/gfx/RR01.png"></P
></DIV
><P
><B
>Figure 2. Set-up for Radiosity test.</B
></P
></DIV
><P
>&#13;		When assigning materials be sure that all of them have the
		<TT
CLASS="literal"
>Radio</TT
> toggle on to enable the <TT
CLASS="literal"
>Shader</TT
>
		Panel of the Material subcontext buttons (<A
HREF="x8197.html#BSG.RAD.F.S68.202"
>Figure 3</A
>). 
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.RAD.F.S68.202"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartR/radiosity/gfx/RR02.png"></P
></DIV
><P
><B
>Figure 3. Radiosity enabled material</B
></P
></DIV
><P
>&#13;		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 <I
CLASS="emphasis"
>downward</I
> pointing normal and the
		<I
CLASS="emphasis"
>outer</I
> cube (the room) should have
		the normals pointing inside, (flip them!)
	</P
><P
>&#13;		Switch to the Radiosity <B
CLASS="guiicon"
>&#13;  		<IMG
SRC="PartR/radiosity/gfx/RadButton.png">
  		</B
> sub-context of the Shading Context. The Panels, shown in 
		(<A
HREF="x8197.html#BSG.RAD.F.S68.203"
>Figure 4</A
>), are two: <TT
CLASS="literal"
>Radio Rendering</TT
>
		which governs Radiosity when used as a rendering tool (present case) and
		<TT
CLASS="literal"
>Radio Tool</TT
>, which governs Radiosity as a modelling tool (next section). 
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.RAD.F.S68.203"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartR/radiosity/gfx/RadButtons.png"></P
></DIV
><P
><B
>Figure 4. Radiosity buttons for radiosity rendering.</B
></P
></DIV
><P
>&#13;		The buttons defines:
       </P
><P
></P
><UL
><LI
><P
><TT
CLASS="literal"
>Hemires:</TT
> - the hemicube
				resolution; the 
            		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.
				</P
></LI
><LI
><P
><TT
CLASS="literal"
>Max Iterations:</TT
> - the maximum number
				of Radiosity iterations. If set to zero Radiosity will go on
				until the convergence criterion is met. You are strongly adviced
				to set this to some non-zero number, usually greater than 100.
				</P
></LI
><LI
><P
>&#13;			<TT
CLASS="literal"
>Mult, Gamma</TT
>
			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 <TT
CLASS="literal"
>Mult</TT
>
			and <TT
CLASS="literal"
>Gamma</TT
> 
            	values. With the <TT
CLASS="literal"
>Mult</TT
> value you can 
			multiply the energy value, 
            	with <TT
CLASS="literal"
>Gamma</TT
> you can change the contrast 
			of the energy values. 
			</P
></LI
><LI
><P
><TT
CLASS="literal"
>Convergence:</TT
> -
				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 in is divided by a factor of 1000 before testing 
		            for that reason.
				</P
></LI
></UL
><P
>&#13;			Set the <TT
CLASS="literal"
>Max Iterations:</TT
> to 100 and turn
			to the Scene Context and Render Sub-context  (<B
CLASS="keycap"
>F10</B
>)
		</P
><P
>&#13;			Locate the <TT
CLASS="literal"
>Radio</TT
> Tog Button 
			(<A
HREF="x8197.html#BSG.RAD.F.S68.204"
>Figure 5</A
>) in the <TT
CLASS="literal"
>Render</TT
>
			panel and set it on to enable Radiosity, then Render! (<B
CLASS="keycap"
>F12</B
>). 
		</P
><DIV
CLASS="figure"
><A
NAME="BSG.RAD.F.S68.204"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartR/radiosity/gfx/RR03.png"></P
></DIV
><P
><B
>Figure 5. Enabling Radiosity in the Rendering Buttons.</B
></P
></DIV
><P
>&#13;		The rendering will take some more time than usual, in the console
		you will notice a counter going on. Result will be quite poor 
		(<A
HREF="x8197.html#BSG.RAD.F.S68.205"
>Figure 6</A
>, left) because the automatic 
		radiosity render does not do adaptive refinement!
	</P
><P
>&#13;		Select all meshes, one after the other, and, in EditMode
		subdivide it at least three times. The room,
		which is much bigger than the others, you can even
		subdivide four times. Set the <TT
CLASS="literal"
>&#13;		Max Iterations</TT
> a bit higher, 300 or more.
		Try again the Rendering (<B
CLASS="keycap"
>F12</B
>).
		This time the rendering will take even longer but
		the results will be much nicer, with soft shadows
		and colour leaking 
		(<A
HREF="x8197.html#BSG.RAD.F.S68.205"
>Figure 6</A
>, right)
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.RAD.F.S68.205"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartR/radiosity/gfx/RR04.png"></P
></DIV
><P
><B
>Figure 6. Radiosity rendering for coarse meshes (left) and
		fine meshes (right).</B
></P
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>&#13;		In the Radiosity Rendering Blender acts as for a
		normal rendering, this means that textures, Curves,
		Surfaces and even Dupliframed Objects are handled correctly.
	</P
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