From a12571c709c5af840bb89c43344bd982a496f21a Mon Sep 17 00:00:00 2001
From: Jannik Vogel <email@jannikvogel.de>
Date: Sat, 21 May 2016 01:04:57 +0200
Subject: OpenGL: Implement fog

---
 src/video_core/renderer_opengl/gl_shader_gen.cpp | 34 ++++++++++++++++++++----
 1 file changed, 29 insertions(+), 5 deletions(-)

(limited to 'src/video_core/renderer_opengl/gl_shader_gen.cpp')

diff --git a/src/video_core/renderer_opengl/gl_shader_gen.cpp b/src/video_core/renderer_opengl/gl_shader_gen.cpp
index ea7ab2883..3bace7f01 100644
--- a/src/video_core/renderer_opengl/gl_shader_gen.cpp
+++ b/src/video_core/renderer_opengl/gl_shader_gen.cpp
@@ -555,6 +555,7 @@ layout (std140) uniform shader_data {
     int alphatest_ref;
     float depth_scale;
     float depth_offset;
+    vec3 fog_color;
     vec3 lighting_global_ambient;
     LightSrc light_src[NUM_LIGHTS];
     vec4 const_color[NUM_TEV_STAGES];
@@ -563,6 +564,7 @@ layout (std140) uniform shader_data {
 
 uniform sampler2D tex[3];
 uniform sampler1D lut[6];
+uniform usampler1D fog_lut;
 
 // Rotate the vector v by the quaternion q
 vec3 quaternion_rotate(vec4 q, vec3 v) {
@@ -580,6 +582,12 @@ vec4 secondary_fragment_color = vec4(0.0);
         return out;
     }
 
+    out += "float z_over_w = 1.0 - gl_FragCoord.z * 2.0;\n";
+    out += "float depth = z_over_w * depth_scale + depth_offset;\n";
+    if (state.depthmap_enable == Pica::Regs::DepthBuffering::WBuffering) {
+        out += "depth /= gl_FragCoord.w;\n";
+    }
+
     if (state.lighting.enable)
         WriteLighting(out, config);
 
@@ -596,14 +604,30 @@ vec4 secondary_fragment_color = vec4(0.0);
         out += ") discard;\n";
     }
 
-    out += "color = last_tex_env_out;\n";
+    // Append fog combiner
+    if (state.fog_mode == Regs::FogMode::Fog) {
+        // Get index into fog LUT
+        if (state.fog_flip) {
+            out += "float fog_index = (1.0 - depth) * 128.0;\n";
+        } else {
+            out += "float fog_index = depth * 128.0;\n";
+        }
 
-    out += "float z_over_w = 1.0 - gl_FragCoord.z * 2.0;\n";
-    out += "float depth = z_over_w * depth_scale + depth_offset;\n";
-    if (state.depthmap_enable == Pica::Regs::DepthBuffering::WBuffering) {
-        out += "depth /= gl_FragCoord.w;\n";
+        // Generate clamped fog factor from LUT for given fog index
+        out += "float fog_i = clamp(floor(fog_index), 0.0, 127.0);\n";
+        out += "float fog_f = fog_index - fog_i;\n";
+        out += "uint fog_lut_entry = texelFetch(fog_lut, int(fog_i), 0).r;\n";
+        out += "float fog_lut_entry_difference = float(int((fog_lut_entry & 0x1FFFU) << 19U) >> 19);\n"; // Extract signed difference
+        out += "float fog_lut_entry_value = float((fog_lut_entry >> 13U) & 0x7FFU);\n";
+        out += "float fog_factor = (fog_lut_entry_value + fog_lut_entry_difference * fog_f) / 2047.0;\n";
+        out += "fog_factor = clamp(fog_factor, 0.0, 1.0);\n";
+
+        // Blend the fog
+        out += "last_tex_env_out.rgb = mix(fog_color.rgb, last_tex_env_out.rgb, fog_factor);\n";
     }
+
     out += "gl_FragDepth = depth;\n";
+    out += "color = last_tex_env_out;\n";
 
     out += "}";
 
-- 
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