qt-everywhere-src-5.15.1/qtquick3d/src/runtimerender/res/effectlib/depthpass.glsllib

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#ifndef DEPTHPASS_GLSLIB
#define DEPTHPASS_GLSLIB 1

float calculateVertexDepth( vec2 cameraProperties, vec4 position )
{
    float camera_range = cameraProperties.y - cameraProperties.x;
    return 1.0 - ((position.w - cameraProperties.x) / (camera_range));
}

#if __VERSION__ <= 120
float modf(in float val, out float integer)
{
    integer = floor(val);
    return val - integer;
}
#endif

vec4 outputDepth( float vert_depth )
{
    float integer_portion = 0.0;
    float fraction = modf((vert_depth * 255.0), integer_portion);
    return vec4( integer_portion / 255.0, fraction, 0, 1.0 );
}

float getDepthValue( vec4 depth_texture_sample, vec2 cameraProperties )
{

#if __VERSION__ >= 300
    float zNear = cameraProperties.x;
    float zFar = cameraProperties.y;
    float zRange = zFar - zNear;
    float z_b = depth_texture_sample.x;
    float z_n = 2.0 * z_b - 1.0;
    float z_e = 2.0 * zNear * zFar / (zFar + zNear - z_n * (zRange));
    return 1.0 - ((z_e - cameraProperties.x) / (zRange));
#else
    return depth_texture_sample.x + (depth_texture_sample.y / 255.0);
#endif
}

float depthValueToLinearDistance( float depth_value, vec2 cameraProperties )
{
    float FarClipDistance = cameraProperties.y;
    float NearClipDistance = cameraProperties.x;
    float DepthRange = FarClipDistance - NearClipDistance;
    float linearDepth = NearClipDistance + (DepthRange * (1.0 - depth_value));
    return linearDepth;
}

#endif