forums.ps2dev.org

[dr_watson]

Introduction

JGE++ (Jas Game Engine++) is a hardware accelerated 2D game engine for PSP (using GU) and Windows. It's inspired by the popular game engine HGE on MS Windows. In fact the Windows' counterpart is basically a wrapper of HGE.

For more information about HGE, please visit its web site at:

http://hge.relishgames.com.

With JGE++, you can build a project as a Windows executable or a PSP EBOOT image with the same source code without any modification. This means the game development process, including coding, debugging and testing, can be done mainly in Windows. However, since JGE++ is still under development and not heavily tested, it is recommended that the PSP EBOOT image should be built and put onto a PSP for testing from time to time just to make sure everything is working properly.

Of course you may also put in platform specific codes with #if/#else/#endif.

SkyAnimator is introduced with JGE++ v0.2b. It is a visual tool written by
HuangYZ for creating sprite animations. HuangYZ has ported the runtime library to JGE++ and this gives JGE++ a very powerful animation system to play with.

Contents of the JGE++ package

- JGE++ v0.2b (source + lib)
- SkyAnimator lib
- JGE++ demo (source + assets)
- SkyAnimator demo (source + assets)
- StarBugz (source + assets)
- Mario Demo (source + assets)


Prerequisites

libpng
libz
mikmodlib


Directory Structure

[dr_watson]

An introduction to rendering 2D images with GU

JGE++ uses the GU functions for rendering and this is an introduction on how the 2D rendering is done with this 3D library.

PSP has 2MB video RAM. Apart from using as frame buffers, user textures can also be stored here for faster GPU process. The pixel format that is chosen for the game will have a big impact on how many textures can be stored in the video RAM.

There are four different pixel formats available on PSP:

PSP_DISPLAY_PIXEL_FORMAT_565 //16-bit RGB 5:6:5
PSP_DISPLAY_PIXEL_FORMAT_5551 //16-bit RGBA 5:5:5:1
PSP_DISPLAY_PIXEL_FORMAT_4444 //16-bit RGBA 4:4:4:4
PSP_DISPLAY_PIXEL_FORMAT_8888 //32-bit RGBA 8:8:8:8

Since transparent colour is pretty much needed for all game applications, the 565 format is basically out. The 5551 and 4444 format both take 2 bytes for a single pixel. If effects such as alpha blending is required, then the 4444 format will be the choice to use.

Of course, the optimal option will be the 8888 format, which produce the maximum number of colours on screen. However this format uses 4 bytes for each pixel. A primary frame buffer plus a back buffer will take up 512x272x4x2 = 1,088KB. There will be only 960KB left for user textures. In that case, most of the textures will need to be stored in system RAM and thus will slow down all the rendering.

Here is the code segment on GU intialization:

[dr_watson]

Hello World for JGE++

The JGE++ package comes with a demo application called Demo. This is basically a Hello World program for JGE++.

When programming 2D games, in order to show an image on screen, the image is loaded and then a "DrawImage" function is used to do the job. Sometimes a few images are packed into a single one and portions of it are used for rendering in order to save file space, for easy management or for whatever reasons.

With hardware accelerated 2D game engines, this "packed" image approach has become a necessary because the width/height of the texture that is fed to the graphics hardware need to be in the power of 2. And also, switching from one texture to another may take some extra GPU cycles. Obviously the best way to do is to have a relative large texture, say 512x512, and putting all images in it and render portions of it for different sprites. In practice of course it is not required to have just one single texture for a whole game. But keeping the number of textures to a minimal is a good habit anyway!

Here is a sample texture (128x128) with a cartoon character and the text "HELLO WORLD":



A quad structure is used to specify which area of the large texture is to be rendered. Here is an example on how to load a texture and render an image to screen in JGE++:

[Brunni]

Cool ^^
Was it originally designed for Windows or PSP (or both at once)?
_________________
Sorry for my bad english
Oldschool library for PSP - PC version released

[dr_watson]

It was written for PSP while I was making StarBugz. Since I borrowed lots of ideas from HGE, I knew I would make a kind of HGE wrapper to make JGE++ games run on Windows as well. It's really painful to debug programs on PSP directly. I made the Mario Demo almost entirely in M$ Windows. Occasionally I would put it on my PSP for some "real" testing ;)

[dot_blank]

nice work :)
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[dr_watson]

SkyAnimator English version is available now:

SkyAnimator (English version)

[Shapyi]

Great work. I like the fact you included the source code so we can learn from it. I'm gonna check out the samples.

[alain91]

Hello dr_watson,

It seems great but when I try to launch demo project, it hangs with a blue screen :) and registers dump ?

[dr_watson]

Is it Windows build or PSP build?

For PSP, there's a "res" folder in the "bin" folder of each project. Did you put that on PSP together with your EBOOT?

[ipsp]

Nice work.

I've had a quick look whilst I was at work yesterday, and I must say the examples gave some insight into it abilities, hence making it standout for other libraries.

I'll investigate this more once I finish my current project. Again nice work good to see more libararies added to the PSP community.

[dr_watson]

Thank you for all the good words!

Here are some prebuilt binaries of the included demos for people to check out the features of JGE++:

JGE++ Demo for PSP firmware 1.50
JGE++ Demo for Windows
SkyAnimator Demo for PSP firmware 1.50
SkyAnimator Demo for Windows
Mario Demo for PSP firmware 1.50
Mario Demo for Windows
StarBugz Prototype for PSP firmware 1.50
StarBugz Prototype for Windows

[alain91]

Hello dr_watson,

The problem was only on demo program. Mario & others work well.

[subbie]

Yo, just simple question. Why use GU_TRIANGLE_STRIP to render sprites? You can just use GU_SPRITES insted. You just need to suply the upper left & lower right verticies to form a quad.

[dr_watson]

[alain91]

dr_watson : The prebuit demo work well :)

[dr_watson]

A new bug-fixed version of SkyAnimator is available for download and the URL is at the original post.

[alain91]

hello dr_watson,

I wondered how you would code a scrolling map with jge ?

- a big sprite where you put tiles in it ?
- a direct memory access ?
- ..?

Thanks a lot,
Alain

[Brunni]

You draw multiple sprites, each one corresponding to one tile.
_________________
Sorry for my bad english
Oldschool library for PSP - PC version released

[alain91]

Thanks Brunni ;)

Just wondering if your lib is better than this...

[dr_watson]

hi alain91, you can have a look of the Mario demo. It features parallax scrolling. The very front layer is a tile map while the other layers are just big images.

I reckon OSLib has more features but JGE++ offers M$ Windows' support, which makes it easier for the development ;)

However, from Brunni's posts I think he's aiming at Windows support too :)

[alain91]

Hello dr_watson,

Windows support for testing is a sure 'plus' :)

So you use sprites to build a map.. wouldn't it be faster and less ressources consuming to have a 'blit' functions (direct draw from tiles to memory) ?

Sorry if it is a stupid question, Brunni oslib seems to use the same system as you ..

Regards,
Alain

[dr_watson]

Hi Alain,

By "draw from tiles to memory", do you mean you have a large image in memory for the background, you blit all tiles to that image to construct the background and then render that large image to screen?

If you are to use GU functions to render that large image, the size of it need to be within 512x512, which is the largest texture size GU supports. Anything larger than that will require you to play some tricks to render them properly.

Since GU functions are hardware accelerated, there's no problem to render few dozens of tile images at each frame for the tile map. For example, with that Mario Demo, you got 300-400 FPS. Not fast enough? ^^

[Brunni]

alain91> I don't think you can compare both libraries, it's up to you to test them to find the most adapted to you ;)
And to answer your question, direct memory blitting is not better than using "sprites", as they are hardware accelerated.
The advantage of using sprites lets you mix pixelformats (for example draw a 16-bit tilemap on a 32-bit drawbuffer) and is more flexible. You can for example enable transparency and then display your map => it will be transparent, and so on.
_________________
Sorry for my bad english
Oldschool library for PSP - PC version released

[Panajev2001a]

[Brunni]

Yes. The map size is not limited (unlike the GBA), but all tiles must fit in a single image (and its maximum size is 512x512, it's a limitation of the PSP GPU).
_________________
Sorry for my bad english
Oldschool library for PSP - PC version released

[Panajev2001a]

[subbie]

[dr_watson]

[subbie]