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/*
Copyright (c) 2019 The Khronos Group Inc.
Use of this source code is governed by an MIT-style license that can be
found in the LICENSE.txt file.
*/
#ifdef GL_ES
precision mediump float;
#endif
/* This epsilon will work as long as the magnitude of the float is < 128.
* This can be seen by taking the spec relative mediump precision of 2^-10:
* 0.125 / 2^-10 = 128
*/
#define ERROR_EPSILON (0.125)
void main (void)
{
float x;
// Declare a constant 4 by 4 matrix with unique elements.
const mat4 a = mat4( 1.0, 2.0, 3.0, 4.0,
5.0, 6.0, 7.0, 8.0,
9.0, 10.0, 11.0, 12.0,
13.0, 14.0, 15.0, 16.0);
// Copy the constant matrix to another non-const matrix.
mat4 b = a;
// Check each element of the copy.
bool elms = true;
if(b[0][0] != 1.0) elms = false;
if(b[0][1] != 2.0) elms = false;
if(b[0][2] != 3.0) elms = false;
if(b[0][3] != 4.0) elms = false;
if(b[1][0] != 5.0) elms = false;
if(b[1][1] != 6.0) elms = false;
if(b[1][2] != 7.0) elms = false;
if(b[1][3] != 8.0) elms = false;
if(b[2][0] != 9.0) elms = false;
if(b[2][1] != 10.0) elms = false;
if(b[2][2] != 11.0) elms = false;
if(b[2][3] != 12.0) elms = false;
if(b[3][0] != 13.0) elms = false;
if(b[3][1] != 14.0) elms = false;
if(b[3][2] != 15.0) elms = false;
if(b[3][3] != 16.0) elms = false;
// Add up each row of the copy.
bool rows = true;
x = b[0][0] + b[1][0] + b[2][0] + b[3][0];
if(x < 28.0-ERROR_EPSILON || x > 28.0+ERROR_EPSILON) rows = false;
x = b[0][1] + b[1][1] + b[2][1] + b[3][1];
if(x < 32.0-ERROR_EPSILON || x > 32.0+ERROR_EPSILON) rows = false;
x = b[0][2] + b[1][2] + b[2][2] + b[3][2];
if(x < 36.0-ERROR_EPSILON || x > 36.0+ERROR_EPSILON) rows = false;
x = b[0][3] + b[1][3] + b[2][3] + b[3][3];
if(x < 40.0-ERROR_EPSILON || x > 40.0+ERROR_EPSILON) rows = false;
// Add up each column of the copy.
bool cols = true;
x = b[0][0] + b[0][1] + b[0][2] + b[0][3];
if(x < 10.0-ERROR_EPSILON || x > 10.0+ERROR_EPSILON) cols = false;
x = b[1][0] + b[1][1] + b[1][2] + b[1][3];
if(x < 26.0-ERROR_EPSILON || x > 26.0+ERROR_EPSILON) cols = false;
x = b[2][0] + b[2][1] + b[2][2] + b[2][3];
if(x < 42.0-ERROR_EPSILON || x > 42.0+ERROR_EPSILON) cols = false;
x = b[3][0] + b[3][1] + b[3][2] + b[3][3];
if(x < 58.0-ERROR_EPSILON || x > 58.0+ERROR_EPSILON) cols = false;
// Check if all of the operations were successful.
float gray = elms && rows && cols ? 1.0 : 0.0;
// Assign the fragment color.
gl_FragColor = vec4(gray, gray, gray, 1.0);
}
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