| |
| /* |
| ** Copyright (c) 2012 The Khronos Group Inc. |
| ** |
| ** Permission is hereby granted, free of charge, to any person obtaining a |
| ** copy of this software and/or associated documentation files (the |
| ** "Materials"), to deal in the Materials without restriction, including |
| ** without limitation the rights to use, copy, modify, merge, publish, |
| ** distribute, sublicense, and/or sell copies of the Materials, and to |
| ** permit persons to whom the Materials are furnished to do so, subject to |
| ** the following conditions: |
| ** |
| ** The above copyright notice and this permission notice shall be included |
| ** in all copies or substantial portions of the Materials. |
| ** |
| ** THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| ** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| ** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
| ** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
| ** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
| ** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
| ** MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS. |
| */ |
| |
| |
| #ifdef GL_ES |
| #extension GL_OES_standard_derivatives : enable |
| precision mediump float; |
| #endif |
| |
| // setting a boundary for cases where screen sizes may exceed the precision |
| // of the arithmetic used. |
| #define SAFETY_BOUND 500.0 |
| |
| // Macro to scale/bias the range of output. If input is [-1.0, 1.0], maps to [0.5, 1.0]. |
| // Accounts for precision errors magnified by derivative operation. |
| #define REDUCE_RANGE(A) ((A) + 3.0) / 4.0 |
| |
| |
| uniform float viewportwidth; |
| uniform float viewportheight; |
| |
| varying vec2 vertXY; |
| |
| void main (void) |
| { |
| const float M_PI = 3.14159265358979323846; |
| float cosine; |
| |
| if( (gl_FragCoord.x < SAFETY_BOUND) && (gl_FragCoord.y < SAFETY_BOUND) ) |
| { |
| // vertical abs cosine wave with a period of 128 pixels |
| |
| #ifdef GL_OES_standard_derivatives |
| cosine = REDUCE_RANGE(abs(cos(fract(gl_FragCoord.y / 128.0) * (2.0 * M_PI)))); |
| #else |
| cosine = 0.5; |
| #endif |
| |
| gl_FragColor = vec4(cosine, cosine, cosine, 1.0); |
| } |
| else discard; |
| } |
| |