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43 lines
1.3 KiB
Plaintext
43 lines
1.3 KiB
Plaintext
2 years ago
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// xs_begin
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// author : 'ephtracy'
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// arg : { var = 'm_side' name = 'Side' value = '3' range = '3 64' step = '1' precision = '0' }
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// arg : { var = 'm_angle' name = 'Angle' value = '0' range = '0 360' step = '5' precision = '0' }
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// xs_end
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//===== built-in args =====
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// uniform vec3 i_volume_size; // volume size [1-256]
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// uniform float i_color_index; // current color index [0-255]
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// uniform int i_num_color_sels; // number of color selections [1-255]
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//===== built-in functions =====
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// float voxel( vec3 v ); // get voxel color index
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// float color_sel( float k ); // get kth selected color index
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// vec4 palette( float index ); // get palette color
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// 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 ) )
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float map( vec3 v ) {
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const float PI = 3.1415926;
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// model center
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vec3 center = i_volume_size * 0.5;
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// 2D pos
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vec2 u = ( v - center ).xy;
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// poly
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float angle = PI * 2.0 / max( floor( m_side ), 3.0 );
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float t = min( center.x, center.y );
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// polar coord
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float r = length( u );
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float theta = atan( u.y, u.x ) + PI + m_angle / 180.0 * PI;
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r *= cos( angle * abs( fract( theta / angle ) - 0.5 ) );
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t *= cos( angle * 0.5 );
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r = max( r, 0.0 );
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t = max( t, 0.0 );
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return i_color_index * step( r, t );
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}
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