initial commit

1 files changed, 100 insertions, 0 deletions

diff --git a/res/shaders/framebuffer.fs b/res/shaders/framebuffer.fs
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+++ b/res/shaders/framebuffer.fs
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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. Just some trigonomety
+
+    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);
+        }
+    }
+}