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| 1 |
| 2 /* |
| 3 ** Copyright (c) 2012 The Khronos Group Inc. |
| 4 ** |
| 5 ** Permission is hereby granted, free of charge, to any person obtaining a |
| 6 ** copy of this software and/or associated documentation files (the |
| 7 ** "Materials"), to deal in the Materials without restriction, including |
| 8 ** without limitation the rights to use, copy, modify, merge, publish, |
| 9 ** distribute, sublicense, and/or sell copies of the Materials, and to |
| 10 ** permit persons to whom the Materials are furnished to do so, subject to |
| 11 ** the following conditions: |
| 12 ** |
| 13 ** The above copyright notice and this permission notice shall be included |
| 14 ** in all copies or substantial portions of the Materials. |
| 15 ** |
| 16 ** THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| 17 ** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| 18 ** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
| 19 ** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
| 20 ** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
| 21 ** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
| 22 ** MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS. |
| 23 */ |
| 24 |
| 25 |
| 26 #ifdef GL_ES |
| 27 #extension GL_OES_standard_derivatives : enable |
| 28 precision mediump float; |
| 29 #endif |
| 30 |
| 31 // setting a boundary for cases where screen sizes may exceed the precision |
| 32 // of the arithmetic used. |
| 33 #define SAFETY_BOUND 500.0 |
| 34 |
| 35 // Macro to scale/bias the range of output. If input is [-1.0, 1.0], maps to [0
.5, 1.0].. |
| 36 // Accounts for precision errors magnified by derivative operation. |
| 37 #define REDUCE_RANGE(A) ((A) + 3.0) / 4.0 |
| 38 |
| 39 uniform float viewportwidth; |
| 40 uniform float viewportheight; |
| 41 |
| 42 varying vec2 vertXY; |
| 43 |
| 44 void main (void) |
| 45 { |
| 46 const float M_PI = 3.14159265358979323846; |
| 47 float cosine; |
| 48 |
| 49 if( (gl_FragCoord.x < SAFETY_BOUND) && (gl_FragCoord.y < SAFETY_BOUND) ) |
| 50 { |
| 51 // horizontal abs cosine wave with a period of 128 pixels |
| 52 |
| 53 #ifdef GL_OES_standard_derivatives |
| 54 cosine = REDUCE_RANGE(abs(cos(fract(gl_FragCoord.x / 128.0) * (2
.0 * M_PI)))); |
| 55 #else |
| 56 cosine = 0.5; |
| 57 #endif |
| 58 |
| 59 gl_FragColor = vec4(cosine, cosine, cosine, 1.0); |
| 60 } |
| 61 else discard; |
| 62 } |
| 63 |
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