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/****************************************************************************
**
** Copyright (C) 2014 NVIDIA Corporation.
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt 3D Studio.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
** approved by the KDE Free Qt Foundation. The licenses are as published by
** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef TESSELLATION_LINEAR_GLSLLIB
#define TESSELLATION_LINEAR_GLSLLIB
#if TESSELLATION_CONTROL_SHADER
layout (vertices = 3) out;
// global setup in main
vec3 ctWorldPos[3];
uniform vec3 camera_position;
uniform vec2 distanceRange;
uniform float disableCulling;
float isBackFace()
{
vec3 faceNormal = normalize( cross( ctWorldPos[2] - ctWorldPos[0], ctWorldPos[1] - ctWorldPos[0] ) );
vec3 ncd = normalize( ctWorldPos[0] - camera_position );
return sign( dot(faceNormal, ncd) );
}
float adaptiveCameraFactor( in float minTess, in float maxTess )
{
float distanceValue0 = distance( camera_position, ctWorldPos[0] );
float distanceValue1 = distance( camera_position, ctWorldPos[1] );
float distanceValue2 = distance( camera_position, ctWorldPos[2] );
float range = distanceRange[1] - distanceRange[0];
vec3 edgeDistance;
edgeDistance[0] = ((distanceValue1 + distanceValue2) / 2.0) / range;
edgeDistance[1] = ((distanceValue2 + distanceValue0) / 2.0) / range;
edgeDistance[2] = ((distanceValue0 + distanceValue1) / 2.0) / range;
edgeDistance = clamp( edgeDistance, vec3(0.0), vec3(1.0) );
//float af = mix( minTess, maxTess, 1.0 - edgeDistance[gl_InvocationID] );
float af = 1.0 - edgeDistance[gl_InvocationID];
af = clamp( af*af*maxTess , minTess, maxTess );
return af;
}
void tessShader ( in float tessEdge, in float tessInner )
{
float bf = isBackFace();
bf = max(disableCulling, bf);
// adapative tessellation factor
float af = adaptiveCameraFactor( tessInner, tessEdge );
// Calculate the tessellation levels
gl_TessLevelInner[0] = af * bf;
gl_TessLevelOuter[gl_InvocationID] = af * bf;
}
#endif
#if TESSELLATION_EVALUATION_SHADER
layout (triangles, equal_spacing, ccw) in;
vec4 tessShader ( )
{
vec4 p0 = gl_TessCoord.x * gl_in[0].gl_Position;
vec4 p1 = gl_TessCoord.y * gl_in[1].gl_Position;
vec4 p2 = gl_TessCoord.z * gl_in[2].gl_Position;
vec4 pos = p0 + p1 + p2;
return pos;
}
#endif
#endif
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