Blow: Checkerboard Rendering on PS4Pro Isn’t Completely Free, There Might Be Better Uses of the Power
After the announcement of PlayStation 4 Pro, several developers have confirmed their support for the enhanced console due to be released by Sony on November 10th.
One such developer is Thekla, the studio behind The Witness. Creator Jonathan Blow published a blog post with some details of the PS4 Pro patch the team is preparing, which is a bit different from the plans announced by other developers.
He was called out on the Neogaf board for not choosing to enable downsampling for those playing at 1080P, for instance, and he promptly answered with an explanation.
Actually, no, we care a lot about it. We are trying to carefully make decisions based on what is going to provide the highest image quality.
For example, we think doubling MSAA will give us a better result than rendering double the number of pixels and downscaling -- it's faster, and leaves more performance on the table for other features.
Examples of other features are things I mentioned in the posting, like having a longer streaming distance before the high-res meshes turn into low-res LODs. I think that kind of LOD popping has a much bigger effect on visual quality than some extra pixels that just get downscaled again anyway. So if we are able to put some of the GPU power into that, we feel it is the better choice.
HOWEVER, we might not be able to increase the LOD radius very much, because that also requires memory, and we are already pushing the boundaries of the console's memory. In that case we might have GPU power to burn, in which case maybe we might render at a resolution higher than 1080p, with 4x MSAA also, and then downscale.
But if I announce that right now, and then we end up not doing it, we will get a lot of people yelling at us for betraying them. So what I announced is the minimum that we can definitely do. And, as I said in the posting, none of this is completely final, and we will announce the final tech specs when the patch is done.
In a subsequent post, he explained why checkerboard rendering (a technique that's already proving to be popular on PS4 Pro, as we explained yesterday) might not necessarily be the best use of the console's additional power, especially since it's not completely free performance wise (despite being supported via hardware).
I think it depends on the particular game and engine. Different rendering pipelines are structured differently; for some pipelines, the cost of adding checkerboard rendering would be very low, because they are already computing a lot of the information that checkerboard rendering needs. For other pipelines the cost might be higher. In our case we're just not sure of the total cost yet, but we think it is probably high enough that we may prefer to do a straight upscale. But we're not completely sure.
(It is true that, as Sony has announced, the PS4 Pro provides hardware support for checkerboard rendering that makes it faster than it would otherwise be. I think in some places I have seen the rumor that checkerboard is completely free, but I would consider that an exaggeration: the cost is going to vary per game. Unfortunately due to NDAs I can't provide details; I can't say anything more about Sony technologies than what they have announced. It is definitely true that if you had a game running on the original PS4, and the developer wants to do the most straightforward thing to make the game look better on the Pro, that developer could enable checkerboard rendering and the game will look better and run faster; so it's "free" in that sense. But if you are going to get picky about how you are spending the GPU memory and bandwidth of the new machine, then there are tradeoffs here, like with anything.)
It'll be interesting to see how different developers choose to use PlayStation 4 Pro (and, when it releases, Xbox One Scorpio) hardware.