56 lines
2.4 KiB
GLSL
56 lines
2.4 KiB
GLSL
/********************************************************************
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KWin - the KDE window manager
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This file is part of the KDE project.
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Copyright (C) 2008 Martin Gräßlin <ubuntu@martin-graesslin.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(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, see <http://www.gnu.org/licenses/>.
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*********************************************************************/
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uniform float width;
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uniform float cubeAngle;
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uniform float xCoord;
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void main()
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{
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gl_TexCoord[0].xy = gl_Vertex.xy;
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vec4 vertex = gl_Vertex.xyzw;
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float radian = radians(cubeAngle*0.5);
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// height of the triangle compound of one side of the cube and the two bisecting lines
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float midpoint = width*0.5*tan(radian);
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// radius of the circle
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float radius = (width*0.5)/cos(radian);
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// the calculation does the following:
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// At every x position we move on to the circle und create a new circular segment
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// The distance between the new chord and the desktop (z=0) is the wanted z value
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// The length of the new chord is 2*distance(x,middle of desktop(width*0.5))
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// Now we calculate the angle between chord and radius as acos(distance/radius)
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// With this angle we can can calculate the height of the new triangle (radius-distance*2-radius)
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// The height is the opposite leg of the triangle compound of distance-*height*-radius
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// New height minus old height (midpoint) is the looked for z-value
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// distance from midpoint of desktop to x coord
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float distance = width*0.5 - (vertex.x+xCoord);
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if( (vertex.x+xCoord) > width*0.5 )
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{
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distance = (vertex.x+xCoord) - width*0.5;
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}
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float angle = acos( distance/radius );
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float h = radius;
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// if distance == 0 -> angle=90 -> tan(90) singularity
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if( distance != 0.0 )
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h = tan( angle ) * distance;
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vertex.z = h - midpoint;
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gl_Position = gl_ModelViewProjectionMatrix * vertex;
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}
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