interior rendering / GI color bleed

[cpan]

hmmm i don't have probs with FG multibounce (except slow glossy rendering :\...).
Be sure to set your light trace depth to Number Of Bounces (NOB) + 1 and aswell the global Shadow Depth to NOB+1 and also use a tonemapper (such as lastest ctrl_buffers version) to make contrasty cool images.

good luck :)

[Arcon]

i can't be sure whether FG multibounce has any merit unless you post an image of an interior render you've done with it. i've seen plenty of cool contrasty images in the forums which look more artistic than they do photorealistic.

ctrl_buffers has some workflow issues that make it not practical on large scale projects, and then there's the render-time issue of having to use 1-3 sampling ;)

[cpan]

i can't be sure whether FG multibounce has any merit unless you post an image of an interior render you've done with it. i've seen plenty of cool contrasty images in the forums which look more artistic than they do photorealistic.

FG multibounce is cool because it's much easier to setup than classic FG+GI but currently the main limitations are that it gets slow with many bounces (i mostly use 1-2-3 bounces) and, the most important, it's slow with glossy surfaces. Tough this will probably get fixed in mentalray 3.5 @ Maya 8 ;)

ps heres a multibounce test i've just rendered (1 bounce) after messing with texturing for some time :)
it took 28 minutes to render on my 3000+ A64.
http://img438.imageshack.us/img438/1159/howardbroomtest4ho9.png
@ scene by HowardB
i know there are some material probs but i'll fix those tomorrow :)


ctrl_buffers has some workflow issues that make it not practical on large scale projects, and then there's the render-time issue of having to use 1-3 sampling ;)


hmmm what issues? i find it pretty easy to use ctrl_buffers's tonemapper... just several clicks and it doesnt increase rendering time... :surprised

[Arcon]

hey thanks for posting that image - its looking good but the problem i'm having is kinda different, i'm finding with any FG solution the walls all look to evenly lit (all the same brightness). this probably wouldn't be a problem in that image because looking at the shadows i'm guessing there is a light directly hitting those walls on the center/right?

this issue only really shows up if you render a big interior, and have one outside light source (sun), in the areas that aren't receiving direct light the walls look very even. with GI at least i can still get realistic decay and disperssion of light inside the room, which is how it would look in real life, but its way too dark. increasing photon intensities creates unrealistic bleed. (lol, it would be cool if there was some setting that lets shaders receive the brightness value of photons but can scale the hue/saturation ..? ;) ).

anyway back to FG, i was able to get a better falloff result by adding a point light inside the interior, whereever there is a window, and making them exclusive to the walls and cieling, this also helps create a nice bright bloom on the roof which FG can't do very well by itself. i know its a fake but hey what isn't in cg, i'll post an image when i've got something decent :)



hmmm what issues? i find it pretty easy to use ctrl_buffers's tonemapper... just several clicks and it doesnt increase rendering time... :surprised


using ctrl_buffer for 6.5, i found that images are aliased really badly unless using 1-3 sampling (which is totally insane). i read about this limitation in the archives too. if there's a way around it please let me know ;) also is it true that every new shader needs a new buffer_write node? this will make workflow too long on scenes of 100+ shaders... but maybe i'll still give it a go on the next project if the sampling issue can be resolved. i havn't used the tonemapper and would be keen to check it out - is it available for 6.5...?

[cpan]

hey thanks for posting that image - its looking good but the problem i'm having is kinda different, i'm finding with any FG solution the walls all look to evenly lit (all the same brightness). this probably wouldn't be a problem in that image because looking at the shadows i'm guessing there is a light directly hitting those walls on the center/right?


this issue only really shows up if you render a big interior, and have one outside light source (sun), in the areas that aren't receiving direct light the walls look very even. with GI at least i can still get realistic decay and disperssion of light inside the room, which is how it would look in real life, but its way too dark. increasing photon intensities creates unrealistic bleed. (lol, it would be cool if there was some setting that lets shaders receive the brightness value of photons but can scale the hue/saturation ..? ;) ).



i think you didn't increase the shadow depth trace (on both the light -if you're using maya lights- and in Render Globals), that's what's causing washed out illumination. BTW set the shadow trace depth to number of bounces (FG Reflection) + 1.
As for the dark with Photons, as you said, you shouldn't increase the photon intensity, keep it the same as the light's intensity (if you use mentalray lights, otherwise i think you need to multiply by ~4 the light intensity to get the right photon intensity, phot int = 4*light int). Just change the gamma to 0.45 in the framebuffer settings (or set gamma to 2.2 later in PS), then adjust the contrast in PS. That's pretty much all you can do since maya 6.5's ctrl_buffers is old and doesn't have the great tonemapping from ctrl_buffers 2.0... though you could try to install the 2.0 and see if it gives any errors since both are using mr 3.4



anyway back to FG, i was able to get a better falloff result by adding a point light inside the interior, whereever there is a window, and making them exclusive to the walls and cieling, this also helps create a nice bright bloom on the roof which FG can't do very well by itself. i know its a fake but hey what isn't in cg, i'll post an image when i've got something decent :)


:D


using ctrl_buffer for 6.5, i found that images are aliased really badly unless using 1-3 sampling (which is totally insane). i read about this limitation in the archives too. if there's a way around it please let me know ;) also is it true that every new shader needs a new buffer_write node? this will make workflow too long on scenes of 100+ shaders... but maybe i'll still give it a go on the next project if the sampling issue can be resolved. i havn't used the tonemapper and would be keen to check it out - is it available for 6.5...?

it might work but smth tells me in doesnt :shrug:
btw no, to use the tonemapper you don't need an huge setup.
you either attach the buffer_write to the camera and enable tonemapping on it, or attach buffer_api as a geom shader on a dummy surface and then with 2 clicks anything is set up. Pretty fast workflow and very cool (the dummy method) is that you can preview the tonemapping in the FG phase and rendering ;)

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