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POInconsistent artifacts when rendering textures in OpenGLES 2.0
 

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  1. POInconsistent artifacts when rendering textures in OpenGLES 2.0
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    <p>I'm just trying to render some simple particles in OpenGLES 2.0 in the iPhone Simulator, and sometimes there are artifacts, and sometimes there aren't, it's almost like it's a coin flip when I try to run my code. The first image is what it should look like, the second image are the artifacts, notice the lines/banding at the bottom. Same image, same code, different results, it has me stumped:</p> <p><a href="http://i.imgur.com/C6LnoWj.png" rel="nofollow">http://i.imgur.com/C6LnoWj.png</a> &lt;-no artifacts</p> <p><a href="http://i.imgur.com/EBj26kG.png" rel="nofollow">http://i.imgur.com/EBj26kG.png</a> &lt;-artifacts</p> <p>Like I said, I have no idea where to begin, it's just a basic two triangle sprite with texture coordinates of (0,0), (0,1), (1,0), and (1,1). If you have any suggestions of what code I should post, I would appreciate it</p> <p>Edit:</p> <p>Here's my texture loading code.</p> <pre><code>CGImageRef image = [UIImage imageNamed:filename].CGImage; size_t width = CGImageGetWidth(image); size_t height = CGImageGetHeight(image); NSUInteger length = width*height*4; GLubyte *data = (GLubyte*)malloc(length*sizeof(GLubyte)); CGContextRef context = CGBitmapContextCreate(data, width, height, 8, width*4, CGImageGetColorSpace(image), kCGImageAlphaPremultipliedLast); CGContextTranslateCTM(context, 0, height); CGContextScaleCTM(context, 1.0, -1.0); CGContextDrawImage(context, CGRectMake(0, 0, width, height), image); CGContextRelease(context); GLuint texture; glGenTextures(1, &amp;texture); glBindTexture(GL_TEXTURE_2D, texture); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data); </code></pre> <p>I switched the malloc call to calloc based on the suggestion to zero out the memory first, and that seems to have fixed it.</p>
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    1. USDevin
    1. USDevin
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    1. COI'm not going to post this as an answer since I don't know the exact solution, but I think I can hint at the problem. It looks like you have a race condition where you are using a texture possibly before it is finished copying into memory. Try to make use of the GL wait and sync operations if possible.
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      1. POInconsistent artifacts when rendering textures in OpenGLES 2.0
      1. USborrrden
    2. COHow are you loading the sprite images? Are you using CoreGraphics? Is the memory zeroed before you load into it?
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      1. POInconsistent artifacts when rendering textures in OpenGLES 2.0
      1. USFrogblast
    3. COHere's my texture loading code:
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      1. POInconsistent artifacts when rendering textures in OpenGLES 2.0
      1. USDevin
 

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