An interesting "dirt map"

[Gaieus]

Hi all,

Some of you may remember my Roman Basilica project WIP's from "down under" the gallery forum.

It seems that I am getting close to finish it and am making test renders - obviously with low settings for testing reasons.

This is when I ran across this curious phenomenon you can see mainly at the bottom-ish of the apse walls in this render. It looks like some cool dirt map was applied but no, there is nothing like that. I rendered it with Easy > Low+ and of course I can imagine there is simply not enough light in the scene and something weird is going on. Also the roof tiles (from inside) on the apse should be exactly the same - not different like it can be seen now (in fact, they are the same faces vertically-radially).

Anyway, "enjoy":

proba3.jpg (425.07 KiB) Viewed 5625 times

At the moment, I am rendering this interior with Interior Progressive (not +) as a spherical panorama at 4000x2000 pixels. It's coming along nice although I have been rendering it for 13h 15' and it has just finished its 31st pass.

A question - is this interior progressive is the ideal preset for such a scene with no interior lights? I am planning to put some lights in later so eventually I will definitely use this preset but what if there are no lights inside? Would the "Exterior progressive" be not better? That is basically for a single light source (sun) generally AFAIK.

[Fletch]

I would not use exterior progressive for this scene (an interior)... as that setting likes a lot of direct light.

Easy 09 would be best for this scene - it is an interior lit only with sun and sky.

To decrease render time, you can increase intensity of sky on the Light Dialog Sky Tab, essentially increasing the "power of the sky" light which comes from all directions.

If you want to try a biased method - try to use Medium+ setting. Or one of the Advanced>Alternate AA methods with a Low+ or Medium or Medium+ in the name

It will also save render time if using unbiased (progressive) rendering to use Sky Portal on openings. Use as few as possible to cover up all fenestration/openings.

Please get the Getting Started with Twilight Light Components Video Tutorial for Twilight and read the reference section of the manual and sky portal threads.

Essentially - the sky portal tells the sun and sky where the openings are, so that all the photons shot from the light sources make it into the openings. Otherwise, only some of them make it in. In unbiased methods (progressive rendering in Twilight) this leads to faster convergence (faster clearing up of the rendering)

RE: interesting dirt map
no, this is simply that you are using low+ to render a scene with little direct light. There are not enough photons or final gathering in that setting to come to a good solution with so little light.
this is, of course, not any sort of problem or 'mistake'... this is the precise reason the name for the setting is "Low" , as in "Low quality". as in "Preliminary rendering setting of low quality"

[Gaieus]

OK Fletch, Thanks for the ideas.
In fact, my Interior progressive rendering is still running but still noisy - and I also thought that there is little light to clear it up (where the sun is directly shining through the windows, it is already fine - just the other parts where less light has been bounced, are grainy).

I also thought to place a huge, invisible emitter as a fake ceiling. I know it would also slow render time down but at least for one, final panorama that I really need to export it would be okay (my current image has been cooked for 31h 25' now so I can handle long render times)

Another thing I may change - paint the columns the same, white(ish) material as the walls. That may bounce a bit more light around and help clean the scene up a bit faster.

[Fletch]

I also thought to place a huge, invisible emitter as a fake ceiling. I know it would also slow render time down but at least for one,

Amount of lights does not negatively effect render times in progressive render methods easy 9-11. (on the contrary, more light usually means quicker rendering in Easy 9-11.

a couple lights (a single emitting rectangular plane) will not increase render times greatly for non-progressive methods. Easy 1-8. I would avoid extra lights with Easy 08.

[Fletch]

updated my comments above to clarify some things.