PSP: Daedalus R8 Delayed (N64 Emulator for PSP)

**irondirgible** · August 21st, 2006, 07:16

According to StrmnNrmn's blog, he has delayed releasing Revision 8 of his fabulous N64 emulator for the PSP in order to optimise newly added code for rendering large triangles. We were all hoping for a release this weekend, but now it looks as if we'll have to wait a little longer, but the speed increase will (hopefully) be worth it.

Read his whole post at:
http://strmnnrmn.blogspot.com/

**V3N0M** · August 21st, 2006, 07:27

Great job irondirgible, for the fast news.
Well here's what StrmnNrmn had to say...

After Wednesday's news I wanted to keep everyone up to date with what I've been working on over the past few days.

With Wednesday's changes incorporated, I reprofiled a few roms to see where most of the CPU time was going. Things have changed considerably since I initially talked about deciding what to optimise. Looking at the profiler for Mario 64 the time spent executing display lists is now a much more significant fraction of the total time spent on each frame. Back around R3/R4 only around 20% of the time was spent here. With the latest build display list processing now accounts for around 35-40% of the time. The display list processing hasn't become any slower, it's just becoming more significant as I've optimised the CPU emulation.

One of the settings I mentioned was worth disabling for a speed boost when I released R7 was the 'Tesselate Large Triangles' option. When this setting is enabled, it causes the display list processor to recursively break up large triangles into smaller pieces. This has been necessary to overcome the PSPs poor hardware clipping support; without breaking the triangles up into smaller pieces, the PSP will often fail to render large triangles as shown below:

Super Mario 64 without clipping

The large triangles that make up the floor that Mario is standing on are rejected by the PSP, leaving a large hole where the floor should be. By breaking the triangles into smaller pieces before attempting to render them, it reduces the chance that the PSP will decide to discard them.

There were a few problems with the 'Tesselate Large Triangles' setting which I've been working on overcoming this weekend. Firstly, it's not perfect - there were plenty of cases where visible triangles would still be culled even when they had been subdivided 3-4 times (which generates 27-81 triangles for each input triangle!). This was always quite noticable in games with a relatively low camera, such as racing games. The other big problem with this setting was that it was very slow - often adding over 20ms per frame.

This setting was always intended as a quick fix rather than a long term solution, so I've been looking at fixing both of these problems over the past few days. I started by ripping out all the exisiting polygon clipping and tesselation code and starting from scratch. After a couple of days of hacking I've finally got a replacement system that seems to be clipping everything I've thrown at it perfectly. Here's a shot of the same location in Mario 64:

Super Mario 64 with new clipping code

Now that I have a working version of the code in place, I'm going to look at optimising it. At the moment the new clipping code is roughly as expensive as the tesselation code, but due to the way it's implemented I think it should be much easier to make work with the PSP's VFPU, as I can process batches of vertices in parallel. Ideally I'd like to get this change into the next release, so I'm going to hold off putting the R8 build together until it's ready. I'll let you know how I get on.

-StrmnNrmn

**Video_freak** · August 21st, 2006, 07:30

Oh well. I can wait!

**BrooksyX** · August 21st, 2006, 07:46

Yeah clipping errors seems to a weakness to the psp. Psmonkey was having a problem with this in iris.

**pkmaximum** · August 21st, 2006, 07:49

I'm actually happy that R8 was delayed, because now this means Strmmmmn can take more time in optomizing his emulator and getting this good for the next release, instead of rushing things. And since we had that unofficial pre-release I think I'll be very patient for the next release. Also Tinnus made me very happy when he said that sound would be not to hard to implement through the PSP Media engine, so I'm really looking foward to that.

**mcvader** · August 21st, 2006, 08:18

Yeah i'm glad it has been delayed, I was hoping R8 would be a big update on that unofficial release from last week. I'm glad he's fixing the clipping, I couldn't bear to play it with tessilate lage tri's off, it just looked so bad, thanks for bringing us the news peep's

**felonyr301** · August 21st, 2006, 08:34

ok so let me get this straight is the new clipping fix for people who still have tesselate tris off or it just only for when its on and us people who have it off wont notice a difference??

**tophead420** · August 21st, 2006, 09:09

cant wait man youv done so good on this so far no need to rush things and i can wait for this release keep up the good work

**jak66** · August 21st, 2006, 09:18

the delay is a good thing
the last release was only recent, if we had another release so soon everyone would be like 'this isnt much better than the last one this is rubbish,lets wait for donkey64, that will be tons better'
...ok maybe not, but still if it was released soon then there would not be a lot of improvement so take your time strmnnrmn