Cho Ren Sha 68K

[attila06]

Hello,

just seen this on Atari Falcon :
[ Show youtube player ]

Do you think it would be possible to port it on Amiga ?

[AnimaInCorpore]

Originally Posted by attila06

Do you think it would be possible to port it on Amiga ?

So now it's up to the Amiga community to make a port of Cho Ren Sha 68k: just visit the Bitbucket Cho Ren Sha 68k for the Atari Falcon 030 repository website to obtain the sources.

Here's a [ Show youtube player ] to get an impression of Cho Ren Sha 68k.

Please let me know if you have questions.

[kovacm]

Maybe it is better to post in coding forum...

[Adrian Browne]

Looks balls hard! So many bullets but I do love shmups.

[-Acid-]

I've played this on a Sharp X68000 at one of the expo's... very good game I hope someone ports it to the amiga.

[Amiga1992]

Seems pretty hard to make on an Amiga, maybe an accelerated one, but then again, not many people have the really fast ones.

[saimon69]

Not a coder but i see it feasible not as port but as rewrite if someone change the bullet routines to use sprites and less colors per enemies; reshoot did show bullet hell is possible but has to be done in a certain way

[Amiga1992]

Reshoot is nowhere near as hectic as this is. Danmaku needs to be a constant bullet fucking rain and Reshoot isn't that way at all, it's a little bit more manic than otehr Amiga shooters, but it isn't "bullet hell", like Cho Ren Sha 68k. So nothing has been proved and I seriously doubt an Amiga can push real danmaku action on the screen.

[Master484]

The Atari Falcon seems quite powerful: https://en.wikipedia.org/wiki/Atari_Falcon

First I thought that this game was running on a standard Atari ST, and that would have indeed been very impressive.

But the Atari Falcon is even more powerful than some 90'ies arcade boards that ran some of those classic "bullet hell" shooters like Batsugun, so seeing something like this on the Falcon isn't really a big surprise.

I believe that the Amiga 1200 at least could surely handle a game like this, the only thing that would cause problems are those big rotating enemies; they would need to be pre-calculated and stored somewhere, to Fast RAM maybe.

---

But even on a normal A500, a game like this could be made, I think Mega Typhoon proves it:

[ Show youtube player ]

Jump to 6:00 in the video to see the boss of the first level; the amount of bullets and big objects on screen is quite similar to what is seen in Cho Ren Sha. And Mega Typhoon has real level backgrounds too.

---

Also drawing lots of bullets and explosions would be very fast with just 2 bitplanes (4 colors)...maybe we could do a dual playfield game where all explosions and bullets would be drawn to a separate 2 bitplane front playfield, and other objects to a higher color back playfield? And of course the copper could boost the 4 colors a little bit ( or quite a lot ).

I know only one Amiga shooter that really takes advantage of the speed of 2 bitplane playfields, and that is the PD shooter "Blaster":

[ Show youtube player ]

In this video the game is played on "Easy" mode, where the aliens don't shoot at all, but on "Hard" mode they shoot, and the screen is full of bullets, but still the game runs at a solid 50fps on a standard A500.

Maybe this technique could be used, but with a 4 bitplane (16 color) back playfield for game objects and a 2 bitplane (4 color) front playfield for bullets and explosions?

[Amiga1992]

Originally Posted by Master484

the only thing that would cause problems are those big rotating enemies; they would need to be pre-calculated and stored somewhere, to Fast RAM maybe.

Do you really need to do that?

Turrican 3 and Mr. Nutz rotate stuff around and I don't think they keep precalc'd copies.

[Codetapper]

Turrican 3 precalcs the rotation gfx in the bit just before it where there is minimal on screen action.

[ExiE]

Originally Posted by Akira

Seems pretty hard to make on an Amiga, maybe an accelerated one, but then again, not many people have the really fast ones.

Maybe it is a time to make first game designed for Vampie (and maybe 040/060)

[Amiga1992]

Originally Posted by Codetapper

Turrican 3 precalcs the rotation gfx in the bit just before it where there is minimal on screen action.

Interesting!

Originally Posted by ExiE

Maybe it is a time to make first game designed for Vampie (and maybe 040/060)

Again, how many people have it? Making a game for a few hundreds doesn't seem very motivating.

Also even if you have a shit ton of CPU on a Vampire, the graphics processors become a bottleneck. A beefy Amiga WITH a videocard might be able to push this, but on standard chipsets, probably not. As it is the Vampire is pushing lots of numbers on the CPU but cannot really do much about those AGA/ECS graphic issues.

[ExiE]

Originally Posted by Akira

Interesting!

Again, how many people have it? Making a game for a few hundreds doesn't seem very motivating.

Also even if you have a shit ton of CPU on a Vampire, the graphics processors become a bottleneck. A beefy Amiga WITH a videocard might be able to push this, but on standard chipsets, probably not. As it is the Vampire is pushing lots of numbers on the CPU but cannot really do much about those AGA/ECS graphic issues.

Vampire means few hundrets atm. After release of A500 version and when you count also owners of 040/060, I think there is enough potential gamers at least in Amiga terms.

[Thorham]

Could be doable on AGA+68030. With AGA you can have three graphics layers: A 4 color sprite layer, and dual playfield for two 16 color layers. Seems to be exactly whats needed for this game. The graphics would have to be recolored to fit the lower number of bits per pixel, of course.

Would be surprised if impossible.

[-Acid-]

It's time games were coded to use graphics cards imo, could P96 be used the same as API's on the PC that way you could just code for P96 and then any compatible graphics card would work?

[frank_b]

Originally Posted by ExiE

Vampire means few hundrets atm. After release of A500 version and when you count also owners of 040/060, I think there is enough potential gamers at least in Amiga terms.

According to the Amiga facebook group, Kipper has thrown in the towel on the vampire.

"Keith Dumoulin From Kipper2k..
Hi All,
i want to let everyone know in more detail why pricing has gone up, There was no possible way that i could get it done, I have spent hours locked up in my room trying to get these completed, as well, i have fallen way behind in other orders as people can testify and this is having an impact wit my sanity and patience. The amount of work and co-ordination required to get this all done is probably harder than what most people think. Add to this the constant flaming about people complaining that this should be handed over to a board house to get this done, and now we have people are complaining about the increased price.
Whenever you import parts bit by bit you can sometimes get them in under the radar, whenever you import expensive items the customs people rub their hands with glee and will gladly accept visa and your first born. Some people are cancelling their orders now and TBH i can understand. When we started this project and decided on the price we wanted to make this available to the masses and expected a small demand for the A600. I will never believe people who say they dont like the A600 as it appears there are at least 1000 active users of the A600. we were naive to think we could get this done at a lower price and people were excited to see this great product at a basement price, (Which it was). Once we made the decision to get the boards done professionally (at the request of a lot of people) we have now offended people at the other end of the spectrum. I have been receiving hate mail from people who are cancelling their orders and being accused of gouging, and multiple other reasons that we have used to increase the price.
I always said when it is no longer fun what i am doing then it is time to stop, So i will stop, Once the Vampire/Phoenix project is complete then it will be time to me to sell off existing bits and pieces and disappear into the woodwork. I am getting too old for this stress,
Thanks to all who supported me and to the rest, goodbye."

[Master484]

About object rotations and other special effects like bending and stretching, I believe that as a general rule these effects are so CPU power costly, that they can never be calculated real time in a running game. This is true especially in shooters like this, where the game action itself already uses almost the entire power that the machine has, constantly drawing as much stuff to screen as possible, while maintaining 50fps...real time rotation calcs simply can't be added on top of that.

Only if there is a special chip to handle the rotations, like the SNES has, then it can be done on-the-fly, but without such chips or a very fast CPU, pre-calculating and storing the frames is the only way. Although I think that some Copper/Blitter tricks exist for stretching stuff vertically ( maybe horizontally too? ), and for creating simple 3D effects like seen in Mr Nutz.

Could be doable on AGA+68030. With AGA you can have three graphics layers: A 4 color sprite layer, and dual playfield for two 16 color layers. Seems to be exactly whats needed for this game.

Indeed, 16 + 16 colors + copper effects + sprites are enough to create a very colorful game. And it should run pretty fast too, if all moving objects are drawn to the Front playfield, so that there is no need to repair the background after every Blit.

Mega Typhoon uses 8 + 8 color dual playfields, and it's super fast on the standard A500. I wonder if the A1200 can achieve the same speed and object amounts on screen using 16 + 16 color playfields? If it can, then surely this game is possible to make, even on an unexpanded A1200.

I noticed that in the coding section people are looking for ideas for an Assembler "coding challenge"...maybe this could be a good challenge: make a "bullet hell" prototype, and see how many bullets and enemies you can put to screen, using either sprites or bobs, or both. 16*16 bullets, with 32*32 enemies, and colorful squares would be enough for graphics.

In fact, I wonder why no-one in the Amiga demoscene hasn't yet done a "bullet hell" game demo, because this game type is one of those classic "Amiga can't handle it" game genres, and people have been saying this for over 20 years now.

[AnimaInCorpore]

Originally Posted by Master484

In fact, I wonder why no-one in the Amiga demoscene hasn't yet done a "bullet hell" game demo, because this game type is one of those classic "Amiga can't handle it" game genres, and people have been saying this for over 20 years now.

Some thoughts about why it's not only difficult to do a 1:1 port of Cho Ren Sha 68k but almost impossible. Well, not impossible with a lot of restrictions, though, but is this what you would expect from the Amiga 1200?

Due to the advantage of dealing with 16 x 16 pixel sprites and create bigger sprites out of them is highly effective on the X68000 which cannot simply be solved by creating Blitter Objects. Seriously, you don't really want only 16 colours for the sprites and 16 more for the background, do you? Others would argue that it wouldn't justifying the usage of the AGA chipset at all.

So if you want to draw all the sprites as 16 x 16 pixels objects (also because the rotation is easier to do it this way), it would result in the worst effective way drawing them on a planar graphics format. E.g. a shifted sprite would need read/modify/write cycles for two words each line and plane. This gets even worse if you really want to use more than 16 colours, i.e. more planes.

Also using more colours the memory consumption of the sprites and the "alternative" coloured sprites (e.g. using another palette like for the "enemy was getting hit" effect or simply to show a different enemy) will add up very fast.

So in conclusion it's a dilemma: a less colourful game will not be accepted by the users because they demand at least a graphically close or even perfect port compared to the original. However, that way is not an option due to the performance and resource limits.

This is the reason why everyone who really knows something about the capabilities of the Amiga 1200 is silent about this.

In fact, I was thinking about porting Cho Ren Sha 68k to the Amiga so some very very early steps can be found in the sources but honestly, I cannot think of a good and fast solution using the planar graphics format for the sprite display.

[Master484]

Yes, it would be a tough conversion for sure, and some compromises would most likely be needed. I don't know so much about the limitations of the A1200, but I'm an Amiga fanatic, and believe that any 2D game is possible to do in an Amiga. And A1200 is the most powerful classic Amiga model, so it simply has to be possible.

Seriously, you don't really want only 16 colours for the sprites and 16 more for the background, do you? Others would argue that it wouldn't justifying the usage of the AGA chipset at all.

I don't know how many colors the Atari Falcon or the X68000 version has, but for me 16 color background + another 16 colors for the moving objects would be enough, with some more colors coming from sprites and copper effects.

And in my opinion this would still make a good use of the AGA chipset, because a 16 + 16 colors dual playfield is something that only AGA can do, and the OCS/ECS cannot.

If you take a look at the A500 game Mega Typhoon, it uses 8 + 8 color playfields, but still looks quite colorful. With 16 + 16 playfield we would have twice as many colors, and with good color choices I'm sure it would look good; and the screen would always have at least 32 colors in it, despite the colors being divided into two separate playfields.

Although some people would of course like to see more colors on screen, but with a game that draws this much stuff, 16 + 16 is most likely the best choice, if we wanted to keep the amount of bullets as close to the original as possible.

---

And if the original game uses 16*16 sprites to draw everything, and that wouldn't work on the A1200, then simply some other drawing method has to be used...and the enemy rotations could even be dropped out, or simplifield somehow.

Also the "Battle Squadron trick" could be used to boost performance; so enemies and enemy bullets would move at 25fps, and player ship (which would be a sprite) + scroll would move at 50 fps.

---

If I would be making this game with Blitz Basic, then I would just go with the 16+16 playfields on an A1200, or 8+8 on an A500. Background to the back playfield, and objects to the front playfield, and Player is a sprite. And everything else would be BOBs (because I don't know how to multiplex sprites in Blitz). And if it didn't run at 50fps (it wouldn't) , then I would just lower the frame rate of the enemies and bullets, while keeping the Player at 50fps.

And with the big screen filling boss aliens, I would do this:
1.
Background is turned black.
2.
Boss alien is put to the back playfield.
3.
Boss alien is drawn to back playfield only once, and after this it is moved by scrolling the back playfield.
4.
Player ship and all bullets (including Boss bullets) are drawn to the front playfield.

So drawing and moving the big bosses would be almost "free", only the bullets would need to blitted every frame (or every second frame) .

With trickery and compromises like this, I think that some sort of a conversion would be possible, even with Blitz Basic, although I doubt that it would run at 50fps.