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Topic: Sibenik Cathedral: An approche to complex interior scenes.

posted by Vladimir Koylazov (VKOYLAZOV)
archived on 1.4.2002

Here are some more images of the Sibenik cathedral:
render time is about half an hour for irradiance map, and about 10 minutes for rendering. The animation took about 8 hours for the imap, and about 2 min per frame.

The last two images show the irradiance map without diffuse bitmaps. The last image shows the samples in the irradiance map (each colored patch corresponds to one sample in the map).

Here is also an animation (requires DivX 5.0 codec). Some post-processed motion blur; AA is not very good and the moblur is not perfect, so I'll render that with VRay's native motion blur:

The irradiance maps for the images were computed with the following settings:

Min rate: -3; Max rate: -2;

Color threshold: 100.0; Normal threshold: 0.5
this means that in practice only the normals were used to decide where to put more samples. Since the cathedral is a difficult scene, you can see from the last .jpg that the samples have very different colors, and so to use the color difference to decide where to put more samples is not a very good idea.

Hemispheric subdivs: 30; Interpolation samples: 8;

Secondary bounces: 5

The irradiance maps were computed at resolution 400x400 for the image and then saved. The final renderings were computed at 800x800 with the Interpolation samples set to 100. Note that the interpolation samples are different during the map calculation and the actual rendering. This saves quite some time during the calculation, and produces a smooth result during the rendering.

Follow-ups

Q: Wouldn't rendering irradiance maps at 400x400 and final renderings at 800x800 be the same as using a lower min/max setting?
A: Yes. But initially I rendered the test images at 400x400, and then just used the saved maps to render the 800x800 final results. I could have also computed the irradiance maps at 800x800 with min rate -4 and max rate -3 which would produce the same result.

Q: Very nice images! Is there any light (omni) at the dome? It's a bit outwashed for me.
A: Nope. No other lights except the skylight and the sun. That's where tone mapping would have been very helpful - it would have got rid of the superbright dome.

Q: How did you keep the renders from coming out blotchy with those settings? I just plugged them into a project I'm working on and blech!
A: Seems like you did not set the interpolation samples to 100 for the rendering...

Q: I have a question about interp. samples: Do they have no impact on the calculation of the irr. map? That means they are only used to interpolate the GI points (that are stored in the irradiance map) during rendering ?
A: The interpolation samples matter both during the map calculation and during rendering. For most precise results, the value should be the same for the calculation and the rendering, but this is not necessary.

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