OpenGL-ES iOS DrawText on screen drops FPS dramastically - ios

Our team has developed an OpenGL application which draws different polygons on the screen. Additionally we want to create about 1000 different strings to print on the screen. If we do this with the Texture2D class the FPS drops down under 3.
I've already tested Bitmap fonts, which doesn't improve the performance.
Which is the best way in OpenGL iOS to draw a lot of text without loss of performance and without losing quality (text should be scalable)?

Allocating 1000 textures takes up a huge amount of memory and will slow down your app, especially if they are at a high enough resolution for readable text. You should generate these textures as they are needed and free them once they are no longer being displayed. Make sure that you aren't generating and freeing textures each frame, but only as needed.
If you are drawing all 1000 strings in the same scene, you should combine as many as you can into like textures. This will allow you to leverage Cocos2D's TrueType rendering system to keep text high-quality. On the other hand if this is not an option and all 1000 strings need to be distinct from each other, consider building a font rendering system that renders each character as a glyph image. This will reduce the number of textures used from 1000 to about 100 to represent all standard English characters and punctuation. I had to do something similar for a video game with lots of dynamic text in an OpenGL environment, and got good performance out of it. However, I do not recommend it unless it's absolutely necessary since it limits your text to only the glyphs you define and you have to program the formatting yourself.

Related

Reducing Flash file size in KB?

I have a Flash file that I need to reduce the size of.
The reason that I need to reduce its size is that I will need to convert this into an iPhone app.
currently it only has 2 buttons and 2 TLF textfileds on the stage one, layer one and the size of the file is 355KB.
I have also placed the code on layer 2.
is there anyway to reduce the size of it so I won't have problems when publishing and sending for app store?
Thanks
The biggest portion of that file size will be related to TLF. TLF (Text-Layout-Framework) is huge and is generally not recommended on mobile (as it has pretty high cpu usage).
If you're not using any TLF specific features, then it would be wise to change your text fields to use classic text instead (DF3).
Beyond TLF, make sure you're using vector objects instead of bitmaps wherever you can as that will drastically reduce file size. If you are using bitmaps, you can play around with the compression settings to optimize file size further. You can do this globally in the Publish Settings (JPEG Quality) or individually on a graphics properties menu.
One note with Vector graphics and mobile, simple vectors will run ok, but complex vectors will run terribly. Make sure to set cacheAsBitmap = true; on any complex (or even all) vectors to improve performance. OR in FLashPRO, click on a movieClip and in the properties panel, go to the "Display" twirl down, and set cache as bitmap in the Render setting.

One background image vs repeating pattern/images, for Corona SDK game?

What would be a better approach in Corona re static background for a 2D scrolling based game?
Let's say the game level "size" is the equivalent of two screens wide and two screens deep.
Q1 - Would one large background image be an OK approach? This would probably be easier as you could do the work in Photoshop to prepare. Or is there a significant advantage (re performance) in Corona to have a small image "pattern" and repeat this in Corona (Lua code) to create the backdrop?
Q2 - If one large background image approach is OK, would I assume that one might have to sacrifice the resolution of the image, noting the size (2xscreens wide, and 2xscreens deep) correct for the higher resolution devices? That is for the iPad 3 say, assuming your configuration would normally would try to pickup the 3x image version (for other images, say smaller play icons, etc.) that for the background you might have to remain with the 1x or 2x image size. Otherwise, it may hit the texture limit (I've read "Most devices have a maximum texture size of 2048x2048"). Is this correct / does this make sense?
I used both approaches on my games.
Advantages of tiled mode:
You can make huge backgrounds.
Can be made to use less memory (specially with smallish tiles with lots of repeating, like a real world wallpaper)
Allow for some interesting effects (like parallax scrolling).
Problems of tiled mode:
Use more CPU performance
Might be buggy and hard to make behave correctly (for example one of my games gaps showed between tiles, but only on iPad Retina... it required some heavy math hackery to make it work)
It is hard to make complex and awesome backgrounds (reason why my point and click adventure games don't use tiled backgrounds).
Pay attention that some devices, has a limit in the size of the textures in pixels, this might be the ultimate limit of how large a single-texture background can be.

What kind of images should go into a spritesheet for a cocos2d ios app?

I apologize upfront for the long question, with multiple subquestions, but the question is really as stated in the title. All that follows is a detailed breakup of different aspects of the question.
In my universal ios game built using cocos2d, I have four categories of images - I want to determine which of them should go into spritesheets and which are better off loaded as individual images. My current guess is that only character animations that run throughout the game provide value being loaded in memory as spritesheets:
Character animations that run throughout the game play (except
when user is in menus): for these, I assume that having the images
in a spritesheet will reduce runtime memory usage (due to the
padding of individual files to power of two byte boundaries), hence
they are candidates for a spritesheet. Is that correct?
Small images (about 200 of them) of which 0 to 4 are displayed at any
time, picked at random, during game play. For these, I am not sure
if it is worth having all 200 images loaded in memory when only at
most any 4 are used at a time. So it may be better to directly
access them as images. Is that correct?
A few (about 20) small menu elements like buttons that are used only in static menus: since the menu items are used only during menu display, I assume they are not of much value in improving memory access via spritesheets. Is that correct?
A few large images that are used as backgrounds for the menus, the game play scene, etc. Most of these images are as large as the screen resolution. Since the screen resolution is roughly equal to the maximum size of a single image (for example, for ipad retina, 4096 x 4096 image size versus screen size of 2048 x 1536), there isn't much gain in using spritesheets as at most 1 or 2 large images would fit in one spritesheet. Also, since each of these large files is used only in one scene, loading all these large images as spritesheets in memory upfront seems like an unnecessary overhead. Hence, directly access them as spritesheets. Is that correct?
A couple of common related questions:
a) Packing images used across different scenes into the same spritesheet makes us load them into memory even when only a subset of the images is used in that scene. I assume that is a bad idea. Correct?
b) There is a stutter in the game play only on older devices (iPad 1 and iPhone 3gs). Will spritesheets help reduce such stutter?
c) I assume that spritesheets are only going to benefit runtime memory footprint, and not so much the on disk size of the app archive. I noticed, for instance, that a set of files which are 11.8 MB in size, when put in a spritesheet are 11 Mb - not much of a compression benefit. Is that a valid assumption?
Please let me know your thoughts on my rationale above.
Thanks
Anand
Rule of thumb: everything goes in a spritesheet (texture atlas), unless there's a good reason not to.
Definitely texture atlas.
Cocos2d's caching mechanism will cause all individual images to be cached and remain in memory, so eventually they'll use more than if they were in a texture atlas. I would only use single images if they're rarely needed (ie menu icons) and I would also remove them from CCTextureCache just after they've been added to the scene, to make sure they will be removed from memory when leaving that menu screen.
Assumption may be wrong. A 320x480 image uses 512x512 as a texture in memory. If you have multiple of them, you may be better off having them all in a single texture atlas. Unless you enabled NPOT support in cocos2d. Again, don't forget that CCTextureCache is caching the textures.
Keep in mind that large textures benefit a lot from spritebatching. So even if there may only be 2-3 images in the texture atlas, it can make a difference in performance.
a) It really depends. If your app is running low on memory, you might want to have separate texture atlases. Otherwise it would be wasteful not to pack the images into a single texture atlas (if possible).
b) It depends on what's causing the stutter. Most common issue: loading resources (ie images) during gameplay, or creating and removing many nodes every frame instead of re-using existing ones.
c) Probably. It may depend on the texture atlas tool (I recommend TexturePacker). It definitely depends on the file format. If you can pack multiple PNG into a single .pvr.ccz texture atlas, you'll save a lot of memory (and gain loading speed).
For more info refer to my cocos2d memory optimization blog post.

iOS: playing a frame-by-frame greyscale animation in a custom colour

I have a 32 frame greyscale animation of a diamond exploding into pieces (ie 32 PNG images # 1024x1024)
my game consists of 12 separate colours, so I need to perform the animation in any desired colour
this I believe rules out any Apple frameworks, also it rules out a lot of public code for animating frame by frame in iOS.
what are my potential solution paths?
these are the best SO links I have found:
Faster iPhone PNG Animations
frame by frame animation
Is it possible using video as texture for GL in iOS?
that last one just shows it is may be possible to load an image into a GL texture each frame ( he is doing it from the camera, so if I have everything stored in memory, that should be even faster )
I can see these options ( listed laziest first, most optimised last )
option A
each frame (courtesy of CADisplayLink), load the relevant image from file into a texture, and display that texture
I'm pretty sure this is stupid, so onto option B
option B
preload all images into memory
then as per above, only we load from memory rather than from file
I think this is going to be the ideal solution, can anyone give it the thumbs up or thumbs down?
option C
preload all of my PNGs into a single GL texture of the maximum size, creating a texture Atlas. each frame, set the texture coordinates to the rectangle in the Atlas for that frame.
while this is potentially a perfect balance between coding efficiency and performance efficiency, the main problem here is losing resolution; on older iOS devices maximum texture size is 1024x1024. if we are cramming 32 frames into this ( really this is the same as cramming 64 ) we would be at 128x128 for each frame. if the resulting animation is close to full screen on the iPad this isn't going to hack it
option D
instead of loading into a single GL texture, load into a bunch of textures
moreover, we can squeeze 4 images into a single texture using all four channels
I baulk at the sheer amount of fiddly coding required here. My RSI starts to tingle even thinking about this approach
I think I have answered my own question here, but if anyone has actually done this or can see the way through, please answer!
If something higher performance than (B) is needed, it looks like the key is glTexSubImage2D http://www.opengl.org/sdk/docs/man/xhtml/glTexSubImage2D.xml
Rather than pull across one frame at a time from memory, we could arrange say 16 512x512x8-bit greyscale frames contiguously in memory, send this across to GL as a single 1024x1024x32bit RGBA texture, and then split it within GL using the above function.
This would mean that we are performing one [RAM->VRAM] transfer per 16 frames rather than per one frame.
Of course, for more modern devices we could get 64 instead of 16, since more recent iOS devices can handle 2048x2048 textures.
I will first try technique (B) and leave it at that if it works ( I don't want to over code ), and look at this if needed.
I still can't find any way to query how many GL textures it is possible to hold on the graphics chip. I have been told that when you try to allocate memory for a texture, GL just returns 0 when it has run out of memory. however to implement this properly I would want to make sure that I am not sailing close to the wind re: resources... I don't want my animation to use up so much VRAM that the rest of my rendering fails...
You would be able to get this working just fine with CoreGraphics APIs, there is no reason to deep dive into OpenGL for a simple 2D problem like this. For the general approach you should take to creating colored frames from a grayscale frame, see colorizing-image-ignores-alpha-channel-why-and-how-to-fix. Basically, you need to use CGContextClipToMask() and then render a specific color so that what is left is the diamond colored in with the specific color you have selected. You could do this at runtime, or you could do it offline and create 1 video for each of the colors you want to support. It is be easier on your CPU if you do the operation N times and save the results into files, but modern iOS hardware is much faster than it used to be. Beware of memory usage issues when writing video processing code, see video-and-memory-usage-on-ios-devices for a primer that describes the problem space. You could code it all up with texture atlases and complex openGL stuff, but an approach that makes use of videos would be a lot easier to deal with and you would not need to worry so much about resource usage, see my library linked in the memory post for more info if you are interested in saving time on the implementation.

Multilingual Unicode rendering in opengl

I have to extend an OpenGL-Rendering system to support international characters (especially Hebrew, Arabic and cyrillic).
Development platform is Windows(XP|Vista|7), alas using Embercardero Delphi 2010.
I currently use wglOutLineFont(...) to build my font's display list and glCallLists(length(m_Text), UNSIGNED_SHORT, PWchar(m_Text) ) to render my strings.
While this is feasible for Latin-1 Characters, building the full Unicode character set in advance is pretty time-consuming (about 8.5 minutes on my machine), so I am looking for a more efficient solution. I thought about limiting the range from u+0020 - u+077f (Latin, Greek, Cyrillic, Arabic and Hebrew) to include just the glyphs I need, but that would just be a solution for my current needs, and will become insufficient once other encoding is needed.
On the upside, I do not have to worry about left-to right or right-to left direction as our application can handle this already.
I would expect this to be a well-known problem, so I would like to ask if there is any reference material on this on the web, or if you could share some insight on this?
Edit
A clarification: I use a polygonal font representations. Each Font is constructed at unit size (1.0) in advance and scaled appropriately using glScalef(...) before rendering. I did decide against pre-rasterizing since the users might zoom in quite closely (The application is used for CAD), so rastering artifacts would become visible.
Additionally, since a scene seldom exceeds more then a few hundred characters (mainly labels and measurements), the speed gain from pre-rasterization is negligible.
Don't pre-build the display lists :- create an intermediate sprite that builds the lists on demand, and caches them. Trying to pre-compute lists - or pre generate rasterized textures at every font size, font face, and for all characters, is impractical, Especially when you scale to far eastern character sets.
You need to replace the wglOutLineFont.
To do that, generate/render to texture the required glyphs using the wglOutLineFont, and then save the texture into a raster image file. Once application loads, it needs to load the texture image and the glyph texture coordinates (4 coords for each glyph), and to generate the display lists (one list for each glyph, each display list shall draw a single glyph as textured quad).
Each short representing a glyph shall have a corresponding display list (their value much match, and glListBase can aid in this).
I suppose loading a texture is faster than generating font display lists at runtime. Pratically you move offline the glyph raster computation. But the display list generation can be heavy (many glyphs). Indeed you can run in a separated thread the display list generation or generate only the display lists required by your needs.
I've had good luck transliterating this tutorial into C++, though I'm not sure how well it will transfer to Delphi.

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