I’m trying to create a GLSL shader to produce the FAUX HDR effect also known as FAKE HDR, (not to confuse with normal HDR where 3 images with different exposures are combined). I need to create it in a single shader algorithm and not multiple shaders with different passes.
The idea is to achieve images such as in the next links, where the image has high local micro-contrast and intense colors, with mostly important a holo white aura around some edges.
From the steps on the next document I started to build the shader:
So far the next code is my result, the problem is that is really not showing anything near at all of the desired FAUX HDR result.
VERTEX SHADER:
varying vec2 v_texcoord;
void main()
{
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
v_texcoord = gl_MultiTexCoord0.xy;
}
FRAGMENT SHADER:
varying vec2 v_texcoord;
uniform sampler2D texture;
vec3 rgb2hsv(vec3 c)
{
vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));
float d = q.x - min(q.w, q.y);
float e = 1.0e-10;
return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
}
vec3 hsv2rgb(vec3 c)
{
vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
}
void main()
{
vec4 color = texture2D(texture, v_texcoord);
vec3 hsv = rgb2hsv(color.rgb);
float intensity = hsv.z; // the third component holds the brightness
float log_factor = log(intensity + 1.0);
log_factor = exp(log_factor) - 1.0;
hsv.z = log_factor;
color.rgb = hsv2rgb(hsv);
gl_FragColor = color;
}