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#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 eyePosition;
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] - eyePosition );
return sign( dot(faceNormal, ncd) );
}
float adaptiveCameraFactor( in float minTess, in float maxTess )
{
float distanceValue0 = distance( eyePosition, ctWorldPos[0] );
float distanceValue1 = distance( eyePosition, ctWorldPos[1] );
float distanceValue2 = distance( eyePosition, 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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