I want to calculate the distance from the viewpoint/eyepoint to each vertex in my scene then store that value in the r,g,b and a components of a RGBA8 texture… I have gone round in circles trying to figure out how to go from a single 32 bit number to 4 - 8bit numbers. Is the following reasonable? That is… should it work? If not, does anyone know what would?
// Calculate Distance To Each Vertex from vertex position // in eyespace passed as varying from vertex shader float distance = length(eyepoint); // convert distance from floating point to fixed point // with 8 fractional bits float fixedPointDistance = distance * pow(2, 8); // get upper 16 bits int upper16Bits = int(fixedPointDistance/65536); // get lower 16 bits int lower16Bits = int(fixedPointDistance); // get byte1 (or bits 23-31) int byte1 = int(upper16Bits/256); // get byte2 (or bits 16-23) int byte2 = int(upper16Bits*256)/256); // get byte3 (or bits 8-15) int byte3 = int(lower16Bits/256); // get byte1 (or bits 0-7) int byte4 = int(lower16Bits*256)/256); float red = float(byte1/256); float green = float(byte2/256); float blue = float(byte3/256); float alpha = float(byte4/256); gl_FragColor = vec4(red, green, blue, alpha);