// license:BSD-3-Clause // copyright-holders:Sven Gothel #pragma optimize (on) #pragma debug (off) uniform sampler2D color_texture; uniform sampler2D colortable_texture; uniform vec2 colortable_sz; // ct size uniform vec2 colortable_pow2_sz; // pow2 ct size void main() { vec4 color_tex; vec2 color_map_coord; // normalized texture coordinates .. color_tex = texture2D(color_texture, gl_TexCoord[0].st); // GL_UNSIGNED_SHORT GL_ALPHA in ALPHA16 conversion: // general: f = c / ((2*N)-1), c color bitfield, N number of bits // ushort: c = ((2**16)-1)*f; color_map_coord.x = floor( 65535.0 * color_tex.a + 0.5 ); // map it to the 2D lut table color_map_coord.y = floor(color_map_coord.x/colortable_sz.x); color_map_coord.x = mod(color_map_coord.x,colortable_sz.x); gl_FragColor = texture2D(colortable_texture, (color_map_coord+vec2(0.5)) / colortable_pow2_sz); }