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#version 420 core
in vec2 _f_texture;
layout(binding = 2) uniform sampler2D main_colour;
layout(binding = 3) uniform sampler2D main_depth;
layout(binding = 4) uniform sampler2D water_colour;
layout(binding = 5) uniform sampler2D water_depth;
layout(std140, binding = 0) uniform _u_globals {
mat4 proj;
mat4 view;
vec4 frustum[6];
float znear;
float zfar;
float xfov;
float yfov;
int time;
float xwindow;
float ywindow;
};
uniform bool _u_is_underwater;
const vec3 fog_colour = vec3(0.5f, 0.7f, 0.9f);
const vec3 underwater_fog_colour = vec3(0.137f, 0.275f, 0.694f);
out vec4 _o_colour;
vec4 texture_sample(const sampler2D sampler, const vec2 coord) {
return texture(sampler, coord);
}
float depth_sample(const sampler2D sampler, const vec2 coord) {
return texture(sampler, coord).r;
}
float linearise_depth(const float depth) {
const float z = depth * 2.0f - 1.0f; // normalised device coordinates
const float linear_depth =
(2.0 * znear * zfar) / (zfar + znear - (z * (zfar - znear)));
// Usually we would just return linear depth, but this is incorrect! We need
// to account for the additional distance of the frustum away from the
// center of the screen.
const float xsigma = tan(xfov * 0.5) * zfar * _f_texture.x;
const float ysigma = tan(yfov * 0.5) * zfar * _f_texture.y;
const float dist = sqrt(xsigma * xsigma + ysigma * ysigma) / zfar;
const float o_dist = linear_depth * dist;
return sqrt(o_dist * o_dist + linear_depth * linear_depth);
}
float get_fog_intensity(const float distance) {
return clamp(pow((1.0f / (zfar * 0.6f)) * distance, 3.0f), 0.0f, 1.0f);
}
float get_water_intensity(const float distance) {
return 1.0f - exp(0.5 * distance);
}
void main() {
// We recycle the coordinates of our position into our texture coordinates.
const vec2 coords =
vec2((_f_texture.x + 1.0f) / 2.0f, (_f_texture.y + 1.0f) / 2.0f);
const float main_depth = depth_sample(main_depth, coords);
const float main_distance = linearise_depth(main_depth);
const float water_depth = depth_sample(water_depth, coords);
const float water_distance = linearise_depth(water_depth);
_o_colour = texture_sample(main_colour, coords);
if (!_u_is_underwater) {
if (water_depth < main_depth) {
_o_colour =
vec4(mix(vec3(_o_colour.rgb),
texture_sample(water_colour, coords).rgb,
get_water_intensity(water_distance - main_distance)),
1.0f);
}
_o_colour =
vec4(mix(vec3(_o_colour.rgb), fog_colour,
get_fog_intensity(min(main_distance, water_distance))),
1.0f);
} else {
_o_colour = vec4(mix(vec3(_o_colour.rgb), fog_colour,
get_fog_intensity(main_distance)),
1.0f);
if (water_depth < main_depth) {
_o_colour = vec4(mix(vec3(_o_colour.rgb),
texture_sample(water_colour, coords).rgb,
get_water_intensity(-water_distance)),
1.0f);
} else {
_o_colour = vec4(mix(vec3(_o_colour.rgb), underwater_fog_colour,
get_water_intensity(-main_distance)),
1.0f);
}
}
}
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