Refraction Mapping

[PaulS2]

I acts like a reflection map in a raytraced situation…reflections are raytraced till a ray doesn’t hit another object to reflect then the map takes over.

Same with refraction - refraction rays bounce around till they run out - it can go black (termination color) or you can have an image where the rays terminate.

In any glass you have done in EI which has been raytraced, eventually a color (most times black) marked the end of the bounces. How you can specify a map to do the same.

it adds a nice variety and complexity to glass.

[halfworld]

But if I have a 16 core machine in the future, do I need 16 hardrive to take the full renderama advantage? it does sounds ridiculous isn’t it? hope Camera will have true multithreading support before 16 core machine come out…

Hi Loon, a multi-threaded camera would have EXACTLY the same hard drive bottleneck as the current Rama multi-processor support.

There is no solution except to have more hard drives.

So, to confirm, multi-threading does NOT fix this problem. If you only have one hard drive each thread (core) may want to access something on the hard drive (like a texture) but there is only one hard drive ‘head’ so only one process (core) can read/write at a time. However if you have two hard drives you can read and write two things at a time, if you have 6 hard drives you can read and write 6 things at a time… Etc.

It is a common misunderstanding about multi-threading,
I hope that clears it up
Ian

PS. Apologies Paul for the off topic

[halfworld]

does renderama in v7 work with leopard?

In 700 it does not, but 701 will. A wild guess says it it will be released in early January. It is in beta testing now.

Ian

[PaulS2]

[QUOTE=halfworld
PS. Apologies Paul for the off topic :)[/QUOTE]

I sure wouldn’t worry about it:-)

[Tartiflette]

So, to confirm, multi-threading does NOT fix this problem. If you only have one hard drive each thread (core) may want to access something on the hard drive (like a texture) but there is only one hard drive ‘head’ so only one process (core) can read/write at a time. However if you have two hard drives you can read and write two things at a time, if you have 6 hard drives you can read and write 6 things at a time… Etc.

However, reading textures and writing renders to disk aren’t the most demanding tasks in the rendering process, so it’s no big deal when you have big renders or heavy scenes renders.

I DO multithreading in all the renderer i use and using only one HD isn’t a problem for parallelization of the rendering process.

Well, it doesn’t hurt to have 2 HDs though !

Cheers,
Laurent aka Tartiflette

[Reuben5150]

Hi Loon, a multi-threaded camera would have EXACTLY the same hard drive bottleneck as the current Rama multi-processor support.

There is no solution except to have more hard drives.

So, to confirm, multi-threading does NOT fix this problem. If you only have one hard drive each thread (core) may want to access something on the hard drive (like a texture) but there is only one hard drive ‘head’ so only one process (core) can read/write at a time. However if you have two hard drives you can read and write two things at a time, if you have 6 hard drives you can read and write 6 things at a time… Etc.

It is a common misunderstanding about multi-threading,
I hope that clears it up
Ian

PS. Apologies Paul for the off topic

Unless you have SCSI harddrives, if i remember correctly…

The renderama solution is always going to be more demanding on hardware, i don’t have a render farm and only use a single machine, multi-threading makes a lot of sense for a number of reasons…

[juanxer]

I guess you are mentioning SCSI as an advantage because that protocol has some “intelligence” and extra hardware resources for dealing with multiple queued HD IO operations.

(Shouldn’t SATA offer something similar, it being a modern standard and things?)

I wonder if some sort of old-style RAM Disk trick would be helpful there. Are they possible at all on OSes such as OS X and XP?

[halfworld]

Well, there are many read/write intensive tasks in rendering. As you say, more hard drives is always better

But yes, multi-threading makes sense for many reasons. I’m just saying the IO problem is not solved by it (and the IO bottleneck is a big reason why an 8 core machine isn’t 8x faster then a one core machine at doing something - the other big reason being semaphoring but let’s not go into that ;).

Ian

[halfworld]

I wonder if some sort of old-style RAM Disk trick would be helpful there. Are they possible at all on OSes such as OS X and XP?

Really, really interesting point
I even know it has been looked into, I don’t know what came of it though…

Ian

[yhloon]

Hi Loon, a multi-threaded camera would have EXACTLY the same hard drive bottleneck as the current Rama multi-processor support.

There is no solution except to have more hard drives.

So, to confirm, multi-threading does NOT fix this problem. If you only have one hard drive each thread (core) may want to access something on the hard drive (like a texture) but there is only one hard drive ‘head’ so only one process (core) can read/write at a time. However if you have two hard drives you can read and write two things at a time, if you have 6 hard drives you can read and write 6 things at a time… Etc.

It is a common misunderstanding about multi-threading,
I hope that clears it up
Ian

PS. Apologies Paul for the off topic

Hi Ian,
thanks for the clarify, and also agree not to hijack this thread anymore, I wake up so early this morning 6am, enjoying the fresh air, and waiting my EI 7 arrival…

[Reuben5150]

I guess you are mentioning SCSI as an advantage because that protocol has some “intelligence” and extra hardware resources for dealing with multiple queued HD IO operations.

(Shouldn’t SATA offer something similar, it being a modern standard and things?)

I don’t remember the details but SCSI still has some advantages over SATA, its more expensive for a reason google should dig up the info.

Back on topic then ?

[jimjam]

Here’s a quick, rough comparison. In the render with no refraction sky map, the glass is black where rays terminated. Many thanks to Paul for the GI 1-ray bug workaround.

Jim Mulcahy

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