If I want to render just a huge map, what is the best practice when using OpenGL ES with a mobile device (Android or iPhone based)?
What is the best structure to contain all the vertices, normales and texture coordinates?
I guess using a interleaved structure may give you some performance benefits caused by memory caching. Ok?
Should I use drawArrays or drawElements to push my data to OpenGL ES?
Well, I did no testing at all but I might think, that drawElements might be faster if the GFX does not use shared memory since you do not have to push that much data. Since this is really close to metall, what do you think? (the iPhone is ARM based while the Android platform is Qualcomm based (also an ARM?))
Best regards,
Friedrich
In theory using Vertex Buffer Objects should yield the best results. You have already given the reasons.
Although I remember hearing in one of the Stanford lectures on iPhone-development, that the use of VBOs does not produce better performance than using vertex pointers. Then again, this information is a bit dated. So, going for VBOs on the iPhone will definitely not be a bad idea.
Up until Android 1.5 there was a memory leak in the OpenGL-implementation that was triggered by glDrawElements. Although I would assume that it has been fixed by now, I haven't checked it in a while.
And here some Infos on how to best use VBOs.
I like the approach presented in this presentation. Check out slides 26-32.
The presentation is android specific but should apply to the iPhone as well. Basically, check your GL extensions, and if you can use them Vertex Buffer Objects are the way to go.
Remember that your target architecture (ARM in both cases) is probably not going to have an FPU, so state changes are going to be very very expensive.
Related
Can anyone tell me if there is a limit to the maximum number of OpenGL ES calls that can be made on iPad (i.e. OpenGL draw calls and state changes)?
I am working on a game and seeing low FPS, so I wonder if it has any thing to with my large number of OpenGL calls.
There's no real maximum for OpenGL ES commands, but each one does have some overhead associated with it. Redundant state changes should be eliminated, and expensive state changes should be reduced by grouping geometry in ways that everything using one state is drawn, then the next. Apple has some recommendations for this in their OpenGL ES Programming Guide for iOS.
However, I've rarely found the OpenGL ES commands to be the cause of significant performance degradation in my applications. The larger problems tend to be due to the size of your geometry or from the complexity of any shaders or other effects you apply to your scene. I share some tips that I've applied for reducing geometry size here, and one tool for profiling shaders here, but I'm still learning the ins-and-outs of shader tuning myself.
If you do really care about fine-tuning the OpenGL calls you're making, the best profiling tool to use is the new OpenGL ES Analyzer instrument that comes with Xcode 4. I show a couple of example screens from that instrument in my answer here, where I used it to identify some redundant settings. It will find these calls for you, and point out where they are in your code. You can also use Time Profiler to see if you're putting more load on the CPU than you should be when rendering your frames, and track down the offending lines of code.
As far as I know, there is no such limit as maximum number of glCalls. But definitely, the more the number of gl calls, time taken would be more. Batched rendering is one of the main optimizations that has to be made with OpenGL.
Instead of suspecting the bottleneck, use Instruments to locate it.
Trace Template OpenGL ES Analysis is the weapon of choice. Last time I used it, you had to manually attach it to a running process on the device (all other startup options failed).
I've recently been constructing a pixel shader to apply shading to the player-character in a Flash game I'm currently coding for. As it turns out, however, Actionscript 3 is... Not handling this gracefully, and the framerate hit is pretty huge.
What I would like to do is write something in C++ that can then use OpenGL buffers to store the pixels I want to tweak, tweak them in a hardware accelerated fashion, and then pass it back to the Flash file.
Is there any way of getting AS3 to pass bitmap data to a local shader plugin .exe, and then accept returned data back, or should I just give up and rewrite the entire damn thing in Unity or something?
Failing this, is there any way of forcing the GPU to do the number crunching in AS3? I know OpenGL can't be used with AS3, but DirectDraw, perhaps?
I'm aware this entire enterprise is a) ridiculous overkill and b) probably doomed, but it's currently all that's preventing me from having to work on my reflective essay for the project. (University coursework)
You can't interact with any local program. Since Flash Player 10, there is some silly hardware acceleration support, but mostly for video and not for 3D. The best AS3 (Flash Player 10+) can provide is the native support for working with triangles in 3D (method drawTriangles()). For example Flash 3D engine "Away3D Lite" uses this feature.
Have you tried looking at Alchemy?
http://labs.adobe.com/technologies/alchemy/
It is a way of compiling C++ code into the swf bytecode.
I'm using a series of shaders to perform realtime image processing on the iPhone (3GS/4/iPad). The fps isn't what I'd like it to be.
Are there any tools that I can use to help me work out what the bottlenecks are?
I assume you already know that performance tests on the Simulator are worthless and that you're testing on real metal, so Instruments is always a good place to start - specifically in your case you'd be interested in the OpenGL ES and OpenGL ES Analyzer instruments.
Generally speaking for GLSL, there's a list of common GLSL mistakes at the OpenGL.org site. The O'Reilly labs "iPhone 3D Programming" book has some further hints, such as avoiding expensive operations in conditionals, and watching for texture lookups.
Also, it's going to depend on what kind of image processing you're doing; if you're trying to apply heavy Photoshop-esqe filters that would give a quad-core pause to render, it's going to be costly on a lowly phone.
The only currently available tool is the PVRUniSCo editor, which will give you a cycle count for each line of code in your shader (though only on Windows, it seems).
I was watching a video showing an ngmoco rolando2 level designer.
He seemed to be using flash CS4 to make the maps.
Would anyone know how I would go about doing this?
Just in case you need to know, I am an intermediate programmer, I know both Java and Objective-C pretty well.
I don't know if any of what I'm about to say is true or not, but hopefully my input will be helpful:
It could be simply that the level used in Rolando are simply vector graphic images and the designer you saw in the video simply preferred Flash CS4 as his vector editor?
Again, I could be wrong here.
It's also possible that the game has some code that decodes flash files into usable levels somehow - assuming this would be permitted by Apple in regards to their "no interpreters" rules.
My final thought, which in my opinion would be the least likely, is that the game may be a flash game compiled to run on the iPhone using Adobe's beta flash-iphone SDK. I say this would be the least likely as I believe ngmoco haven't used this method in any of their previous games and I don't see why they would suddenly resort to this method of developing iPhone apps.
In my game Hudriks I also used flash to design levels and even make some animations.
There is no any tool to do this, so you need to develop it yourself with requirements for your game.
First of all, it depends on your game and what exactly you need to design in flash - just putting images, defining their parameters (bonus values), ground path, etc.
After that it is important to define structure of your flash file - how you store different levels (in symbols or scenes), what layers for each level you have (boundaries, objects, obstacles, etc).
If you need to have some extra information for you objects in flash, most probably, you will need to develop custom panel in flash to setup all parameters. I used setPersistentData for storing information for flash objects.
After that you need to develop script that goes through all objects in your symbols and extracts basic information, like transformation, and your custom data. I faced some problems with getting correct transformation values, especially for rotation. Had to do extra heuristics.
For animations I just used motion tween data. In my animation framework did simple implementation supporting basic parameters (transformation and alpha) and only linear curves. Fortunately, in Flash CS4 there is function copyMotion that gives you XML for the animation. You just need to parse it or convert to your own format.
I have been developing iPhone Applications for a couple of months. I would like to know your views about the Quartz vs OpenGL ES 1.x or 2.0 learning curve. You can tell your perspective. My Questions are
*I am a wannabe game developer, So is it a good idea to first develop in quartz , then move
on to OpenGL ES or does it not make an difference
*Can you please tell your experiences when you were having the similar question
Thanks :)
Quartz 2D is not applicable for game development IMHO. It is a software rendering API. It won't give you realtime rendering speed. It's good for drawing charts or vector text with shadows, or for blending several images together. Just not for games. Unless you want to make a game where few images are moving against a monochrome background and even in that case I doubt it will be really smooth on older devices. I've seen some games obviously coded with Quartz. A pitiful sight.
Sooner or later you'll end up using Open GL ES or a game framework build on top of it. I recommend you to check cocos2D, SIO2 engine, or examples from SDK.
With careful programming it is possible to make an Open GL ES game with parallax scrolling and relatively small amount of objects work at 60 FPS even on 2nd gen devices. Tiny Wings is an example of such game. And maintaining stable 30 FPS is not a problem at all.
I skipped Quartz and went right to OpenGL ES. I started with a 2D sprite based game. Thought it was pretty easy.
The key is having a good example to look at. I used the Lunar Lander clone (Crash Lander), but I don't think that's easy to find anymore. Maybe someone who has done it recently knows of a better, newer example that uses current best practices.
I'm in the same boat as you describe, although I have no programming background. (Although I don't know what your background is either) Currently, I am in the process of learning to code as I learn the various API's that are available. I'm an objective-c guy going backwards to the c-based Quartz API, and it's a little bit of a challenge. Luckily, Programming in Objective-C 2.0 by S. Kochan has a great chapter on underlying C features to keep you afloat.
I have taken a couple of stabs # OpenGLES, and I have to say, that from a conceptual standpoint, I'm not ready for it. The Quartz2d API is a bit easier to learn conceptually because it's very easy to get up & running with a few commands. Right now, I'm at the point where I can define shapes and point to point images with out too much trouble.
OpenGLES is going to be something in my future, but it takes such an enormous amount of code to configure the drawing view, set up buffers, etc. If you are familiar with everything the code is doing, then it's a bit easier. However, from a learning perspective, Quartz is an easier way to get going, quickly.
Resources I'm using: The aforementioned book, and an anemic amount of blogs containing tutorials, which are limited # best. At this point, make an appointment with the apple docs and get cozy, because it's about the best (free) stuff that's out there (& exhaustive) With that said, I'd love for someone to prove me wrong on this site by posting a great resource for learning, but that's about it. Good Luck.
I have been looking for the fundamental differences so I can decide between OpenGL (ES) or Quartz or a hybrid. The good news is that the hybrid is an option. Clearly Quartz is easier to master for O-O programming and the answer from Apple appears to be that OpenGL, "...is ideal for immersive types of applications..."
http://developer.apple.com/library/ios/#DOCUMENTATION/General/Conceptual/Devpedia-CocoaApp/DrawingModel.html
I don't want to limit the category to games as I believe any game UX can be applied to a business App, a productivity App, entertainment viewing, etc. By the same token, I fully expect the technology (both h/w and s/w) to advance to make either a choice.