edf647f4e5
git-svn-id: http://svn.berlios.de/svnroot/repos/oolite-linux/trunk@3304 127b21dd-08f5-0310-b4b7-95ae10353056
53 lines
1.7 KiB
Plaintext
53 lines
1.7 KiB
Plaintext
/*
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oolite-dust.vertex
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Vertex shader for interplanetary dust.
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© 2010 Jens Ayton
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA.
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*/
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varying vec4 vColor;
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/* The following macros are provided by Oolite, to ensure that they stay in
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sync with the values used in non-shader mode.
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#define OODUST_SCALE_MAX (float(2))
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#define OODUST_SCALE_FACTOR (float(0.002))
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*/
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void main(void)
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{
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float distance = length(gl_ModelViewMatrix * gl_Vertex);
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/* The original non-shader code fades to black using linear fog, with a
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near plane of 500 and a far plane of 1000.
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OODUST_SCALE_MAX is far plane/near plane, and OODUST_SCALE_FACTOR
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is 1.0/(far plane - near plane).
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This gives us a function such that f(x) ≥ 1 when x ≤ near plane,
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f(x) ≤ 0 when x ≥ far plane, and a linear ramp in between, which we
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then clamp to [0..1].
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*/
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float alpha = clamp(OODUST_SCALE_MAX - distance * OODUST_SCALE_FACTOR, 0.0, 1.0);
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vColor = vec4(gl_Color.rgb, alpha * gl_Color.a);
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gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
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}
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