elene@25: varying vec3 pt;
elene@25: 
elene@25: uniform sampler3D tex;
elene@25: uniform float tmin;
elene@25: uniform float tmax;
elene@25: uniform vec3 res;
elene@25: 
elene@25: float transfer(float x, float tmin, float tmax)
elene@25: {
elene@25: 	float dt = 0.25 * (tmax - tmin);
elene@25: 	return smoothstep(tmin - dt, tmin + dt, x) *
elene@25: 		(1.0 - smoothstep(tmax - dt, tmax + dt, x));
elene@25: }
elene@25: 
elene@25: vec3 calc_normal(vec3 p, float texel)
elene@25: {
elene@25: 	vec3 offs = 1.0 / res;
elene@25: 
elene@25: 	float dfdx = texture3D(tex, p + vec3(offs.x, 0.0, 0.0)).x - texel;
elene@25: 	float dfdy = texture3D(tex, p + vec3(0.0, offs.y, 0.0)).x - texel;
elene@25: 	float dfdz = texture3D(tex, p + vec3(0.0, 0.0, offs.z)).x - texel;
elene@25: 
elene@25: 	return normalize(vec3(dfdx, dfdy, dfdz));
elene@25: }
elene@25: 
elene@25: void main()
elene@25: {
elene@25: 	const vec3 ldir = vec3(-1.0, 1.0, 2.0);
elene@25: 
elene@25: 	if(max(pt.x, max(pt.y, pt.z)) > 1.0 || min(pt.x, min(pt.y, pt.z)) < 0.0)
elene@25: 		discard;
elene@25: 
elene@25: 	float texel = texture3D(tex, pt).x;
elene@25: 	float val = transfer(texel, tmin, tmax);
elene@25: 
elene@25: 	vec3 normal = calc_normal(pt, texel);
elene@25: 	float ndotl = max(dot(normalize(ldir), normal), 0.0);
elene@25: 
elene@25: 	gl_FragColor = vec4(ndotl, ndotl, ndotl, val);
elene@25: }