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Hi,
When scaling down large textures for a sprite, it starts to flicker. The flickering is getting stronger as the scale factor decreases.
Is there an openGL setting I can us to reduce this flickering?
Disabling antialiasing makes things worse.
Per default all textures in Cocos2d are drawn with antialiasing enabled. Would I get a performance increase when disabling this for e.g the background texture?
Thanks for any help,
- zombie
Hi,
the flickering is showing when I scale down to 30% of the original size. Its getting worse when I scale to lower values. I have worked around this problem by not using a too big texture. In the cases where I need a higher resolution for it, I will switch to another one. Not perfect, but I think the only way around this.
I think I have to add that the flickering happens only when moving and rotating the sprite!
- zombie
gaminghorror
Member
You might want to consider using mipmaps, this will reduce flickering especially at lower scale factors but not get rid of it. That flickering is caused by aliasing when scaling the texture down. See here to understand the problem: http://en.wikipedia.org/wiki/Aliasing
To lessen the effect you can also try to implement a little motion blurring. By that i mean to render the sprite several times with lesser opacity while scaling down.
Instead of rendering one sprite, you also render the sprite again on top but using the previous scale factor and with reduced opacity. Depending on what your framerate allows you can render 2, 3 or even more sprites at the previous scale factors with decreasing opacity. What you get is a neat blending effect (or cheap anti-aliasing) which i believe could remove some of the flickering. But i haven't tried it, it may also look terrible and drag down performance. ;)
There is an example in the cocos2d project that uses mip maps. See Texture2dTest.m.
Sprite *imgMipMap = [Sprite spriteWithFile:@"logo-mipmap.pvr"];
imgMipMap.position = ccp( s.width/2.0f-100, s.height/2.0f);
[self addChild:imgMipMap];
// support mipmap filtering
ccTexParams texParams = { GL_LINEAR_MIPMAP_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE, GL_CLAMP_TO_EDGE };
[imgMipMap.texture setTexParameters:&texParams];
Interested in this too, but not quite sure how this is supposed to work.
I'm using pngs as pvrtc is giving me too many artifacts.
Assuming I have a 1024x1024 sprite sheet file named sprites1024.png that I load into my AtlasSpriteManager and then use to draw many different AtlasSprites on it. Assuming I use some program to generate a second sprite sheet, this time with 512x512 and call it sprites512.png. Is there a way of getting the AtlasSpriteManager to automatically start using the second file when required?
And if this does work somehow, how does one do the spacing between the individual sprites in the files? In the 1024x1024 file its 1 pixel between the sprites, so what is it in the 512x512 file? 1 pixel? 1/2 pixel? ;)
This is the code I'm talking about:
PVRTexture#createGLTexture
for (NSUInteger i=0; i < [_imageData count]; i++)
{
data = [_imageData objectAtIndex:i];
glCompressedTexImage2D(GL_TEXTURE_2D, i, _internalFormat, width, height, 0, [data length], [data bytes]);
err = glGetError();
if (err != GL_NO_ERROR)
{
NSLog(@"Error uploading compressed texture level: %d. glError: 0x%04X", i, err);
return FALSE;
}
width = MAX(width >> 1, 1);
height = MAX(height >> 1, 1);
}Instead of glCompressedTexImage2D, you should use glTexImage2D.
Don't copy & paste that code because it won't work. It is just a guide of how to generate mipmaps images for a given texture id.
For further info regarding glTexImage2D:
http://www.opengl.org/sdk/docs/man/xhtml/glTexImage2D.xml
actually there is a much easier way to do it:
glBindTexture( GL_TEXTURE_2D, self.name );
glGenerateMipmapOES(GL_TEXTURE_2D);I've just commited it to trunk (example included in Texture2dTest).
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