largest pixel image size in a shader?

[alexx]

should only be stopped by your memory.. i already used 10k.. but no real idea about it.

[anthonymcgrath]

yeah, it seems to be okay putting a 5400pixel image in but having probs when I hit the 5figure mark.

ho hum

[alexx]

i would say RAM will be the biggest issue with it..

try hitting the "use Cache" button below the reload texture button.
like that you can use any size of image you like, but rendering will get slower because a BOT texture gets generated and only 8x8 pixels are loaded to ram for rendering..

[pixho]

Hi Alexx,

Turning On the usecache will convert in the tmp dir your texture file into BOT (block ordered texture) which is the maya file format for mipmapping.
This format stores a predefined resolution of the texture according its actual computed size / raster screen.
The smaller a BOT mapped object will be, the smaller BOT texture resolution will be loaded in ram and used for the render, and to the contrary, the more an object will be close to the camera and subsequently, will need a higher resolution, the highest BOT res. will be loaded in RAM.

It doens't make the render heavier but faster (rendering and image loading) or just during the first time Maya converts the texture in BOT (and not if you manually convert it).
The only disadvantage, is regarding renderfarms: a BOT texture can produce render slowdowns if multiple cpus are loading at the same the same BOT texture.

Just wanted to clarify your post ;-)

Cheers


Emmanuel

[anthonymcgrath]

wow. thanks Emmanuel. That pretty much explains the brunt of it!! nice one.

btw, wicked website. I regularly have a snout round it as should everyone else who hasn't :thumbsup:

[alexx]

hey emmanuel,

i feel a bit anxious answering you about that topic, since i well know your site and i fear you know a lot more than i do.
but what i know about bot files is that it swaps the texture during rendering, by reading only the actual rendered block. and afaik that is always 8x8 pixels.
that is as well the reason why a rendering using bot files is usually slower and extremely slow over a network: it swaps the texture virtually all the time. (you can very well see that in the task editor).

if you have your bot file on another machine than the rendering one (renderfarm with server that holds the data) your speed may drop under 10%.. and that can continuously only happen, when the texture gets swapped all the time - and not just if a lot of machines access it.

it is true, that maya uses that file format for its mipmapping, but it is from my experience not true that it completely loads a bot texture to ram (that only happens, when you dont use "use cache" - then it all ends up in ram - all the mipmap stages)


so..

i hope i was not too wrong with all that.. and bow to you emmanuel for your work and ideas on pixho.. a brilliant site with a lot of great stuff!!

cheers

alexx

p.s.: if i was terribly wrong please tell me that via private mail ;)

[pixho]

Hey Alexx,

No, you're not too wrong!! ;-)

I agree with you that the main prb (and it's clearly written in the doc) with the BOT files is when there are multiple I/O access from cpus to the files.
It can drastically lower the performance of the render.

We faced the prb when I was recently TD on a feature film by copying all the BOT to each respective machine of the render farm (a pre render script did the thing automatically), and it worked out well (as well as we expected at least!! :-))


Emmanuel

[anthonymcgrath]

hi pixho/alexx

wondering if you can help me here. I've been importing my 5400pixel earth map in place of my original 2000pixel earth map. Now originally, the system was dying on import so I turned off hardware texturing in all the viewports and it imported fine.
now when I hit render, it looks like its going to work fine, then I get an 'exception error occured' message at the bottom.
does anyone have any ideas why its doing this? I've tried that 'use cache' button both on and off and still no luck.

am I just crap? :shrug:

ant
newcastle
uk

[alexx]

uhh..

what is the error message exactely?

is it:
memory is low: exception was thrown?

then you might have a problem..

a good check would be to start the render and watch the task manager how much ram you need.
as obvious i dont really go conform with pixho concerning the mem usage of bot files but nevertheless: are you really close to the high res textured object?
are you using polies or nurbs with high tesselation or even adaptive displacement? if so: be carefull.. with the wrong settings a simple plane can fast be a render killer..

describe your scene. because a single 5k image should not be a problem on a reasonable machine..

cheers

alexx

[alexx]

and reasonable machine means 512 MB ram which is quite los i would say..

[anthonymcgrath]

not to worry. I got it sorted. I turned off the "use file cache" in the render globals options and it seemed to be fine. took its time mind on the first frame but the second frame was flicked through!

thanks again.

ant
newcastle
uk

[alexx]

this brings me to another idea:
how much drive space is left on your c: drive? (or whatever drive your TEMP directory is)

everything below 250 megs is not enough :)

cheers

alexx

[anthonymcgrath]

26Gb give or take.

like I said, it seemed to be fine once I turned off the 'use file cache' in the renderglobals it was fine. took its time but did the job! :bounce:

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