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POOpenGL ES 2.0 fragment shader to blur is slow and low quality
 

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  1. POOpenGL ES 2.0 fragment shader to blur is slow and low quality
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    <p>I am trying to write a blur shader for the iPad. I have it working but I am not very happy with the results. I get very choppy frame rates and the blur looks like crap when blur amount is high. </p> <p>Any ideas on how to improve things?</p> <p>Some sample output:</p> <p><img src="https://i.stack.imgur.com/KaCBI.png" alt="alt text"></p> <pre><code>uniform sampler2D texture; varying mediump vec2 fragTexCoord; varying mediump vec3 eyespaceNormal; varying highp float blurAmount; void main(void) { highp vec2 gaussFilter[7]; gaussFilter[0] = vec2(-3.0, 0.015625); gaussFilter[1] = vec2(-2.0, 0.09375); gaussFilter[2] = vec2(-1.0, 0.234375); gaussFilter[3] = vec2(0.0, 0.3125); gaussFilter[4] = vec2(1.0, 0.234375); gaussFilter[5] = vec2(2.0, 0.09375); gaussFilter[6] = vec2(3.0, 0.015625); highp float blurSize = blurAmount * 1.0; ///////////////////////////////////////////////// // 7x1 gaussian blur fragment shader ///////////////////////////////////////////////// highp vec4 color = vec4(0,0,0,1); for( int i = 0; i &lt; 7; i++ ) { color += texture2D( texture, vec2( fragTexCoord.x+gaussFilter[i].x*blurSize, fragTexCoord.y+gaussFilter[i].x*blurSize ) )*gaussFilter[i].y; } gl_FragColor = color; } </code></pre> <p>Edit: A box blur may be the way to go. Here is a box blur version of the shader:</p> <pre><code>highp vec4 color = vec4(0,0,0,1); color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y - 4.0*blurAmount)) * 0.05; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y - 3.0*blurAmount)) * 0.09; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y - 2.0*blurAmount)) * 0.12; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y - blurAmount)) * 0.15; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y)) * 0.16; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y + blurAmount)) * 0.15; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y + 2.0*blurAmount)) * 0.12; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y + 3.0*blurAmount)) * 0.09; color += texture2D(texture, vec2(fragTexCoord.x, fragTexCoord.y + 4.0*blurAmount)) * 0.05; gl_FragColor = color; </code></pre> <p>Here is the box blur output(note it's only a horizontal blur, but it might be enough for what i want) : <img src="https://i.stack.imgur.com/iIsS1.png" alt="alt text"></p>
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