Offscreen polygons lag DS render?

SickleYield

This is something I've never understood, and I'm never one to hesitate in admitting my own ignorance, so:

Does polycount in a scene affect render time when the polygons aren't in front of the camera? This is relevant to me now because I can now afford some of Stonemason large sets, and it appears to me that there's a significant difference in render time if I delete large sections of for e.g. the Cryo Environment set that are not visible in the render.

I'd been assuming that if it's not in front of the camera, it does not affect render time. Is this incorrect?

starionwolf

I think Novica suggested to delete or hide polygons/sections that are not visible in order to increase render time. Apparently, 3Delight is not like other ray-tracers that I have worked with.

My experience is that big scenes slow down the OpenGL preview, but not the 3Delight scenes. Big scenes with many lights can cause long render times. Sorry I couldn't help you out more. Maybe some one else has a better idea.

patience55

SickleYield said:

This is something I've never understood, and I'm never one to hesitate in admitting my own ignorance, so:

Does polycount in a scene affect render time when the polygons aren't in front of the camera? This is relevant to me now because I can now afford some of Stonemason large sets, and it appears to me that there's a significant difference in render time if I delete large sections of for e.g. the Cryo Environment set that are not visible in the render.

I'd been assuming that if it's not in front of the camera, it does not affect render time. Is this incorrect?

If it's visible in the scene [whether in front of the camera or not] yes it'll affect render time. Amongst the items affecting is the calculation for shadows, etc.

It can also help speed render time to turn visibility off on unseen in the render parts too. [like legs under pants].

SickleYield

Patience55 said:

SickleYield said:

This is something I've never understood, and I'm never one to hesitate in admitting my own ignorance, so:

Does polycount in a scene affect render time when the polygons aren't in front of the camera? This is relevant to me now because I can now afford some of Stonemason large sets, and it appears to me that there's a significant difference in render time if I delete large sections of for e.g. the Cryo Environment set that are not visible in the render.

I'd been assuming that if it's not in front of the camera, it does not affect render time. Is this incorrect?

If it's visible in the scene [whether in front of the camera or not] yes it'll affect render time. Amongst the items affecting is the calculation for shadows, etc.

It can also help speed render time to turn visibility off on unseen in the render parts too. [like legs under pants].

It calculates shadows on things that will not be visible in the render?

patience55

SickleYield said:

Patience55 said:

SickleYield said:

This is something I've never understood, and I'm never one to hesitate in admitting my own ignorance, so:

Does polycount in a scene affect render time when the polygons aren't in front of the camera? This is relevant to me now because I can now afford some of Stonemason large sets, and it appears to me that there's a significant difference in render time if I delete large sections of for e.g. the Cryo Environment set that are not visible in the render.

I'd been assuming that if it's not in front of the camera, it does not affect render time. Is this incorrect?

If it's visible in the scene [whether in front of the camera or not] yes it'll affect render time. Amongst the items affecting is the calculation for shadows, etc.

It can also help speed render time to turn visibility off on unseen in the render parts too. [like legs under pants].

It calculates shadows on things that will not be visible in the render?

I think that's what it was doing, yes.

It's also possible to have it calculate shadows but not show up itself in the render, for eg. to have the shadow of a tree in the scene without the tree.

SickleYield

Looks like it does. I ran a quick test.

Loaded CryoEnvironment, CryoLights, and CryoAtmospheric Cameras.

Rendered through Atmospheric Camera 1 zoomed in on blue-lit corridor. 500x500 render. 30 seconds.

Deleted every piece of geometry not visible in the screen, no other changes, re-rendered same size. 20 seconds.

That's ten seconds, yes, but it's also a third of the render time. Looks like deleting individual pieces of these big presets is extremely worth it when they're offscreen.

fixmypcmike

Yes,, things off-camera could nevertheless cast shadows that are in-camera. As for body parts under clothing, 3Delight doesn't know they aren't visible until it does the light calculations, so turning them invisible will speed things up (note that you want visibility turned off -- setting opacity to zero doesn't turn off calculations).

SickleYield

fixmypcmike said:

Yes,, things off-camera could nevertheless cast shadows that are in-camera. As for body parts under clothing, 3Delight doesn't know they aren't visible until it does the light calculations, so turning them invisible will speed things up (note that you want visibility turned off -- setting opacity to zero doesn't turn off calculations).

Sometimes we want or need those shadows, but for the most part it's worth at least checking if I can do without them, I think. Particularly if I'm rendering on one side of a huge cube-shaped thing.

Can't do that with clothing except in private renders - I sell stuff for G1 and G2F, and turning off the body under clothes is a way to deceptively mask pokethrough on these figures (albeit it was a standard practice on Gen 4 back before smoothing and collision existed). They're not really an issue anyway compared to the "giant offscreen sets doubling my render time" thing I've been running into lately.

Thanks for the replies!

Renpatsu

That is one thing that LuxRender taught me right away, to turn off everything that does not have to affect the scene part in the camera in any form - in LuxRender this may be a huge difference. In general it depends a bit on rendering modes, lighting, materials etc. as well due to e.g. light bounce calculations or mentioned shadows, but as a rule of thumb I got used to disabling everything 'not needed'. Some render engines / modes are more 'intelligent' (or more simple) than others and may not be affected by such issues that much.

FirstBastion

It's always a good idea to remove unseen polies. Think of raytraced bounce adding calculation time for a complex model just beyond frame. Environments aren't usually the culprits though, because Stonemason builds very large efficient sets, he can build half a city with hundred thousand polies, whereas some other modeller will use up 100,000 polies on a pair of boots. it's the 50,000 poly clothing items on the character figures just beyond view that adds to render times most often. As mentioned LuxRender user have learned this lesson early on. If it's not seen in scene, get rid of it.

StratDragon

FirstBastion said:

... As mentioned LuxRender user have learned this lesson early on. If it's not seen in scene, get rid of it.

this should be number 1 in the 10 Commandments of LuxRender. (I don't know what the other 9 are yet, )
btw if you make an item invisible in your content pane it will not be transmitted to Reality and exported to LuxRender so you can keep it in your save file for future use and keep it out of your CPU bandwidth at setup and render time. Don't know if it's the same for Luxus 'cus I don't have it.