office-gobmx/vcl/opengl/lineFragmentShader.glsl
Tomaž Vajngerl d18ad8a7fb opengl: shader based polyline rendering - fixes tdf#97137 for OGL
Adds native opengl polyline rendering to draw polylines, line joins
and line caps as triangle strips. The vertex shader allows for the
dynamic line width by calculating the correct vertex posiitons,
and the fragment shader is used for anti-aliasing.

Change-Id: If7982c828cae1fae59c57194c8ac77e5ad7f1d26
2016-02-25 11:16:19 +01:00

36 lines
1.1 KiB
GLSL

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
varying float fade_factor; // 0->1 fade factor used for AA
uniform vec4 color;
uniform float line_width;
uniform float feather;
void main()
{
float start = (line_width / 2.0) - feather; // where we start to apply alpha
float end = (line_width / 2.0) + feather; // where we end to apply alpha
// Calculate the multiplier so we can transform the 0->1 fade factor
// to take feather and line width into account.
float multiplied = 1.0 / (1.0 - (start / end));
float dist = (1.0 - abs(fade_factor)) * multiplied;
float alpha = clamp(dist, 0.0, 1.0);
// modify the alpha chanel only
vec4 result_color = color;
result_color.a = result_color.a * alpha;
gl_FragColor = result_color;
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */