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    <p>Have you tried looking at <a href="http://paulbourke.net/miscellaneous/lenscorrection/" rel="nofollow noreferrer">Paul Bourke's example code for OpenGL</a>? I don't know if it's compatible with OpenGL-ES. Note the feedback about using "glCopyTexSubImage2D instead of doing a slow glReadPixels".</p> <p>AFAICT, Paul Bourke is doing essentially what you said, creating a distorted grid (your "dome object") to lay the image on. According to <a href="https://stackoverflow.com/questions/4279922/algorithm-for-creating-fisheye-effect-from-a-normal-image">this question</a>, that's a good approach.</p> <p><strong>Updated:</strong></p> <p>Or, since iPhone's OpenGL-ES supports shaders (at least in some versions), you could get better performance using a plane distortion technique like <a href="http://adrianboeing.blogspot.com/2011/01/webgl-tunnel-effect-explained.html" rel="nofollow noreferrer">this</a>. You'd just have to change the formulas for <code>uv.x</code> and <code>uv.y</code>. Then you wouldn't need to be concerned about breaking up the image into a grid of small polygons... you'd have single-pixel resolution for free. :-)</p> <p>Hm... maybe you need to define what kind of "fisheye" effect you are looking for. Seems there is <a href="http://paulbourke.net/miscellaneous/domefisheye/fisheye/" rel="nofollow noreferrer">more than one</a>.</p> <p>See also <a href="https://stackoverflow.com/questions/4246143/using-both-programmable-and-fixed-pipeline-functionality-in-opengl">this question</a>.</p> <p><strong>Updated again:</strong></p> <p>Here is some GLSL code I wrote to do a lens effect in a shader. I believe it's a hemispherical fisheye lens. It runs under WebGL, which uses OpenGL ES, so it should be adaptable for iPhone.</p> <pre><code>#ifdef GL_ES precision highp float; #endif uniform vec2 resolution; uniform vec4 mouse; uniform sampler2D tex0; // lens void main(void) { vec2 p = gl_FragCoord.xy / resolution.xy; vec2 m = mouse.xy / resolution.xy; float lensSize = 0.4; vec2 d = p - m; float r = sqrt(dot(d, d)); // distance of pixel from mouse vec2 uv; if (r &gt;= lensSize) { uv = p; } else { // Thanks to Paul Bourke for these formulas; see // http://paulbourke.net/miscellaneous/lenscorrection/ // and .../lenscorrection/lens.c // Choose one formula to uncomment: // SQUAREXY: // uv = m + vec2(d.x * abs(d.x), d.y * abs(d.y)); // SQUARER: uv = m + d * r; // a.k.a. m + normalize(d) * r * r // SINER: // uv = m + normalize(d) * sin(r * 3.14159 * 0.5); // ASINR: // uv = m + normalize(d) * asin(r) / (3.14159 * 0.5); } vec3 col = texture2D(tex0, vec2(uv.x, -uv.y)).xyz; gl_FragColor = vec4(col, 1.0); } </code></pre> <p>To test this, paste it into <a href="http://www.iquilezles.org/apps/shadertoy/" rel="nofollow noreferrer">ShaderToy</a> in a WebGL-enabled browser. Set input 0 to a texture like <a href="http://www.iquilezles.org/apps/shadertoy/presets/tex0.jpg" rel="nofollow noreferrer">http://www.iquilezles.org/apps/shadertoy/presets/tex0.jpg</a> or <a href="http://www.iquilezles.org/apps/shadertoy/presets/tex4.jpg" rel="nofollow noreferrer">http://www.iquilezles.org/apps/shadertoy/presets/tex4.jpg</a></p> <p>Click the play button, and drag the mouse around on the rendering area. The lens is centered on the mouse pointer.</p>
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    1. POAdd Fisheye effect to images at runtime using OpenGL ES
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    1. COjust thinking crazy here, can't i have my 3D model made on Blender or something, then map my texture to that in OpenGLES ? since i can't really rely on shaders for we have support for 3G iPhones
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    2. COSure, if you know how to model such a shape in Blender, and map your texture to it.
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    3. COThis is great stuff LarsH, thank you.
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