The ups and downs of HDRI

The ups and downs of HDRI might as well be a roller coaster. Permit me to share a story.

For the longest time, I thought I couldn’t use the fancy new render engine DAZ rolled out with 4.8: Iray. I longed to play with the photo realistic render engine, but having an AMD video card instead of the NVidia the specs called for, I thought I couldn’t.

Fast forward to just before Christmas 2016 and DAZ 4.9. I made a curious discovery about the list of installed stuff in the install manager: a public beta build of DAZ 4.9. So, I tracked it down among my programs and opened it. Played with it some and got curious about the render settings. What should my curiosity behold, but that NVidia Iray was available to play with!

So, I explored, dabbled and started tracking down tutorials. Fast forward again to about mid March 2017. After multiple not-so-good attempts at making my own HDRIs with Carrara. I still have trouble with the lighting in that one. I was exploring a favorite group for 3D artists on Facebook and stumbled across an image that could be rotated 360 degrees. To go with it, a youtube tutorial video on how the trick was done!

Well, again, I dabbled and played. Made a neat city 360 followed by a scene from Techwarrior #5 and put them on Facebook to a very receptive reaction. I realized I could convert that city 360 to an HDRI and use it as a background for renders. Well, you won’t catch me using 3Delight anymore! Scenes with an HDRI background render very quickly even on my older computer and they look amazing!

HDRIs are wonderful as both light and background, but – and this is the downside – they take a long time to render! Smaller size and resolution just won’t work with these bad boys. The ratio suggested in that tutorial was 2 to 1 with a size of about 4000 by 2000 pixels. Be ready for a long wait unless you’re able to despeckle and sharpen effectively in Photoshop. Here’s what I mean:

Not the greatest picture I’ll admit, but this one’s been at it 14 hours and it’s still pretty grainy.

Personally, I set the render time to 24 hours so it would have plenty of time to render as cleanly as possible. Know how many seconds that is? 86,400 seconds! Now, as I’ve pointed out on Facebook, once this is rendered, it can be used time and again as a background and light source without bogging down the scene I’m trying to render. So, when it comes down to brass tacks, the occasional 24 hour render like this isn’t too horrible, right?

The trick is a simple one, but only available in Iray. Setup a scene with lights but without characters if you want it to be a background HDRI – the one in that picture is a dungeon lit only by fire – and add a camera in the center of it. Go into the camera’s parameters and pick on the lens type. Set it to spherical. Then go into render settings and set the size ratio to 2 to 1 and the pixels to 4000 by 2000. For my 4-year-old laptop, there’s no acceleration from the video card, so I setup the render time at 24 hours or the 86,400 seconds I mentioned before. From there, hit render and walk away for the duration of the render.

It’ll take its time rendering considering the size and and how complicated the scene is, but when it’s done finally, it can be converted to an HDRI and used as a background/light source without being so slow with characters. So, it balances out, wouldn’t you say?

First lesson of the new year!

Happy New Year again! The first lesson of the new year is an incredibly exciting one! For the longest time, scenes have taken quite a while to render, even using DAZ’s less complicated render engine, 3Delight. I made some fantastic scenes that would take up to 10 hours to render mostly because background elements were so complicated. I’ve been trying to find a solution to that problem for a long time, and having discovered it finally, I’ll share my technique with you.

Why would I want to reveal this secret new technique that solves the problem of slow render times because of complicated backgrounds? Well, they say “In teaching you will learn” so I’m going to teach the technique and see if I learn something in the teaching as well.

Let’s say you’ve got this really awesome scene in DAZ. A great background, characters in cool poses, lights and a cool camera angle, but… it’s slower than molasses in January rendering, right? 10, 12 hours and it’s at what? 80%? Especially with Iray. Iray’s definitely heavy-duty, but the renders are impressive, too, right? Take it from someone with an older computer, those long render times are murder on the system and what if DAZ decides to crash mid-render? You’d really want to scream, right? I know I would! Well, what if you could still have an awesome scene, but far less complicated? I can’t say this’ll work for any scene, but it’ll help if you want to do a sweeping mountain vista or broad city.

So, what’s this mysterious secret? I’m coming to that, bear with me a moment. Like you, I’ve lost count how many times I’ve been mid-render on a fabulous scene when DAZ suddenly decided to crash. Worse, after the crash, the program has a hard time opening the file again because it’s so large and complex. Lesson learned: complex scenes might look great, but they’re horribly harsh on the machine trying to render them! Let’s solve that problem together, shall we?

Let’s take a cool city for example. You’ve setup the building props, skydome and anything else you want. That alone is pretty complicated, right? Don’t add those characters yet! Instead, pick the center of your scene and put a level camera in it. You’ll probably want a simple lighting setup, too. Me, I used a basic 3 point light setup, but you can get fancier if you’d like.

I found out the hard way that a 30 frame rotation image series seems to be too many images to line up smoothly, but for my experiment, it served me well. So, render an image series with that camera in a full 360 degree rotation. Probably using fewer than 30 frames. Best to use the Y rotate parameter so you can control the rotation and don’t get any wild rotations. The view cube and similar tools tend to do that, I’ve noticed.

Got that image series rendered? Good! Let’s pop into Photoshop and play with its photo merge. You want it to create a panorama. I’m not going to go into detail on the settings this time, but once the panorama’s created and saved, I put an online image converter to good use. Converting the TIF I made in Photoshop to an HDR for DAZ to use.

Back in DAZ, with Iray on, we hit up the render settings and change the HDR to the one we just made. Presto! Awesome scene is now an HDR background and won’t slow down the render anymore! Instead, characters can be added and render much faster for not having those extra props in the way!

As you can see, my HDRI experiment has some problems, but still works nicely anyway. Solving those problems is next on the agenda and hopefully, once they’re solved, book rendering will be much more realistic and considerably faster. Going back to the self-imposed schedule for releases I had last year, I should be rendering Dream Angel #31 this month. Unfortunately, Dream Angel #24 is next in line, so this new technique should enable me to catch up fast.

Now, if you figure out ways to improve on this new HDRI technique, please don’t hesitate to share! My experimental HDRI turned out misaligned and squished because the technique is new to me. If you figure out how many frames for the image series to render, for instance, don’t hesitate to comment with it!

I’m very well aware that there are some incredible scenes (Stonemason makes some very impressive ones that are high quality, but they’re high poly and tough on the machine trying to render) on the DAZ site, but they’re very hefty on the computer’s resources for rendering, especially in Iray. This technique is to help ease that burden, so let’s help each other out and learn from the basics I’ve taught here. What I’ve shared will get you a basic and quite rough HDRI. Help me fine-tune the technique so it’ll benefit many!