Benefit IR & LC maps [ Final Render ]

[40th]

My goal is to decrease the render time of the final image render.
If i render with low quality settings and save the IR and the LC maps, and render once again with higher settings (same resolution as before), the render will jump right to render phase, thus faster render. The question is, will the second render be High quality or the same as the first one?

[thomthom]

Re: Benefit IR & LC maps [ Final Render ]

It will be higher than the low setting one. But you might risk loosing some details. It really depend on the scene if you'll notice it. Only way is to try it out.

[Micha_cg]

Re: Benefit IR & LC maps [ Final Render ]

If you save the GI cache files and set "read from" for the final pass, than no GI is calculated at the final rendering again. The quality of the saved GI cache determinate the quality of the GI at the final image.

[40th]

Re: Benefit IR & LC maps [ Final Render ]

It will be higher than the low setting one. But you might risk loosing some details. It really depend on the scene if you'll notice it. Only way is to try it out.

I did a test on it. Here are the results:
Low settings: 10 min
High settings + lR and LC maps from the LQ render: 39 min
High settings (no maps): 1h 37 min

I found quality difference between the GI mapped render and the none pre-calculated map render.
So when it comes to quality the none pre-calculated render wins

[40th]

Re: Benefit IR & LC maps [ Final Render ]

If you save the GI cache files and set "read from" for the final pass, than no GI is calculated at the final rendering again. The quality of the saved GI cache determinate the quality of the GI at the final image.

I see... thank you Micha. From your experience when is it efficient to use GI maps?

[thomthom]

Re: Benefit IR & LC maps [ Final Render ]

You can try to create LC and IR maps at a high setting but lower resolution.

[Micha_cg]

Re: Benefit IR & LC maps [ Final Render ]

I use GI cache files for rerender an image with a small change to a texture or something like this without to recalculate the GI.
Also the GI cache can be used to render flytroughs and turntable animations (at Rhino, I'm not sure what can be done per SU). I render the GI to a cache file for some frames (per cache incremmental add ) and later I use the GI cache to render all frames of an animation.

Your test result show it - if you render an image based on a low quality GI cache, than you get an image with GI problems. If you would render a high quality GI cache befor, you would get ... .

[dalomar_cg]

Re: Benefit IR & LC maps [ Final Render ]

In addition to the situations Micha pointed out, saved GI maps are also very good for changing image resolution and dealing with color bleeding. When going from a low res image (screen resolution basically) to a high res image (+1600 px in width or height) there are some changes in your settings that you need to do in order to render that large res image efficiently, with the biggest one being adjusting your min/max rate in your IR settings. Rather than going through the math of figuring out how many times you've doubled your resolution and decreasing your min/max rate accordingly, its much easier to render out a high quality GI solution at your standard screen resolution, save it, and load it up for rendering at the high resolution.

For color bleeding, just apply a different material to whatever is causing the most bleeding, render the GI solutions, save em', switch the material back, and render the final image.

The last reason for saving GI solutions is "render insurance"...If your working on an image that has the potential to crash due to running out of memory, then you don't want to chance starting out a zero if a crash does happen. If you've got saved GI solutions, and the crash happens when rendering the final image, then you don't have to recalculate those solutions which saves you time when you start the render back up again.

There also is a little bit of memory that's saved when using saved GI solutions, but its not too much.