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// xs_begin
// arg : { var = 'm_width' name = 'Width' value = '1' range = '1 128' step = '1' precision = '0' }
// arg : { var = 'm_rise' name = 'Rise' value = '1' range = '0 256' step = '1' precision = '0' }
// arg : { var = 'm_thick' name = 'Thick' value = '1' range = '1 256' step = '1' precision = '0' }
// arg : { var = 'm_dir' name = 'Dir' value = '0' range = '0 3' step = '1' precision = '0' }
// xs_end
//===== built-in args =====
// uniform vec3 i_volume_size; // volume size [1-256]
// uniform float i_color_index; // current color index [0-255]
// uniform int i_num_color_sels; // number of color selections [1-255]
//===== built-in functions =====
// float voxel( vec3 v ); // get voxel color index
// float color_sel( float k ); // get kth selected color index
// vec4 palette( float index ); // get palette color
// generate a new voxel color index [0, 255] at position v ( v is at the center of voxel, such as vec3( 1.5, 2.5, 4.5 ) )
float map( vec3 v ) {
if ( m_dir > 2.5 ) {
v.xy = vec2( v.y, i_volume_size.x - v.x );
} else if ( m_dir > 1.5 ) {
v.x = i_volume_size.x - v.x;
} else if ( m_dir > 0.5 ) {
v.xy = vec2( i_volume_size.y - v.y, v.x );
}
float n = floor( v.x / m_width );
float h = i_volume_size.z - m_rise * n;
if ( v.z > h || v.z < h - m_thick ) {
return 0.0;
}
return color_sel( mod( n + 0.5, float( i_num_color_sels ) ) );
}