Radiosity Question

I just had one of those “smacks hand to forehead” moments. Does anybody know how long ago (versions ago) it was possible to render an image with radiosity without having to collect meshes?? I’m curious to know how much time I have wasted.


2.26 or 2.28. I seem to have lost the release notes but I’ll track them down.


Thanks Fligh %,


is that mode actualy of any use? i played with it few times but never got anything realy usefull in terms of shadows and color bleeding.


This is about what you can expect:

Make sure the objects are subdivided (level 3 or 4) and use a hemires and iterations value of about 500.


“smacks hand to forehead” too :smiley:

I didn’t know you could do that either. What is the difference in the algorithm or is this just a shorcut for the user?


Feature showed up right after the ray tracer was put together. Everyone was ga ga about making animations with radiosity. Haven’t heard too much about animating since then. :slight_smile: My problem is whenever I put together a large scene and subdivide enough to get decent shadows the scene crashes because of the number of verts or something.

From this page:


Without preprocessing needed, while rendering each renderface with ‘emit material’ and each renderface with ‘radio material flag’ set will be used to iterate to a global illumination solution. Per face with high energy (emit) little images are rendered (hemicubes) which makes up lookup tables to ‘shoot’ its energy to other faces.
In the end this energy - color - then is directly added to the pixel colors while rendering, Gouraud shaded.
Since it’s done with renderfaces, it works for all primitives in Blender.

What it doesn’t do yet:

  • take into account textured color of faces. Currently it uses the material RGB color for filtering distributed energy.
  • do some smart pre-subdividing. Right now it means that you’ll have to balance the models yourself, to deliver small faces where you want a high accuracy for shadowing.
  • unified render (is at todo list)

Rendering without lamps:

This is obviously the advantage; animated radiosity:
The specular is done by adding Lamps with “no diffuse” option set.
Note the subtle color bleeding in the head. Its a nice toy!
Check the chin. This is a clear problem with a model moving close through the hemicubes.



  • per Material you want to have included in radiosity render: set the ‘radio’ flag. For newly added Materials it is ON by default now.
  • the Ambient slider in Material controls the amount of radiosity color.
  • for enabling radiosity rendering, set the F10 “Radio” button.
  • the Radiosity buttons now only show the relevant radiosity rendering options. Pressing “collect meshes” will show all buttons again.
  • for meshes, the faces who use Radio material always call the ‘autosmooth’ routine, this to make sure sharp angles (like corners in a room) do not have shared vertices. For some smooth models (like the raptor example) you might increase the standard smoothing angle from 30 to 45 degree.
  • When the ‘hemisize’ (radiosity buttons) is too low, you’ll see aliasing artifacts, especially in smaller faces.
  • While itterating the steps are printed in the console.
  • At the end, the amount of ‘unshot energy’ is printed in the console, this can be used to set a minimum for the Convergence button.


I wish blender’s raytracer would handle radiocity rather than having to increase the geometry to huge levels. But, that’s what Yafray is for. Just would be nice since Yafray is slow.