overBright GLSL

diff --git a/src.cmake b/src.cmake
index 54ad95a45..33c2a1a95 100644
--- a/src.cmake
+++ b/src.cmake
@@ -188,6 +188,8 @@ set(GLSLSOURCELIST
     ${ENGINE_DIR}/renderer/glsl_source/liquid_vp.glsl
     ${ENGINE_DIR}/renderer/glsl_source/motionblur_fp.glsl
     ${ENGINE_DIR}/renderer/glsl_source/motionblur_vp.glsl
+    ${ENGINE_DIR}/renderer/glsl_source/overBright_fp.glsl
+    ${ENGINE_DIR}/renderer/glsl_source/overBright_vp.glsl
     ${ENGINE_DIR}/renderer/glsl_source/portal_fp.glsl
     ${ENGINE_DIR}/renderer/glsl_source/portal_vp.glsl
     ${ENGINE_DIR}/renderer/glsl_source/reflection_CB_fp.glsl


diff --git a/src/engine/renderer/gl_shader.cpp b/src/engine/renderer/gl_shader.cpp
index 099452671..b508eb48b 100644
--- a/src/engine/renderer/gl_shader.cpp
+++ b/src/engine/renderer/gl_shader.cpp
@@ -35,6 +35,7 @@ ShaderKind shaderKind = ShaderKind::Unknown;

 // *INDENT-OFF*

+GLShader_overBright                      *gl_overBrightShader = nullptr;
 GLShader_generic2D                       *gl_generic2DShader = nullptr;
 GLShader_generic                         *gl_genericShader = nullptr;
 GLShader_lightMapping                    *gl_lightMappingShader = nullptr;
@@ -1545,6 +1546,12 @@ void GLShader::SetRequiredVertexPointers()
    GL_VertexAttribsState( ( _vertexAttribsRequired | _vertexAttribs | macroVertexAttribs ) );  // & ~_vertexAttribsUnsupported);
 }

+GLShader_overBright::GLShader_overBright( GLShaderManager *manager ) :
+   GLShader( "overBright", "overBright", ATTR_POSITION | ATTR_TEXCOORD | ATTR_QTANGENT, manager ),
+   u_LightFactor( this )
+{
+}
+
 GLShader_generic2D::GLShader_generic2D( GLShaderManager *manager ) :
    GLShader( "generic2D", "generic", ATTR_POSITION | ATTR_TEXCOORD | ATTR_QTANGENT, manager ),
    u_TextureMatrix( this ),


diff --git a/src/engine/renderer/gl_shader.h b/src/engine/renderer/gl_shader.h
index f2b7c9e88..66cc94cf4 100644
--- a/src/engine/renderer/gl_shader.h
+++ b/src/engine/renderer/gl_shader.h
@@ -2393,6 +2393,14 @@ class u_Lights :
    }
 };

+class GLShader_overBright :
+   public GLShader,
+   public u_LightFactor
+{
+public:
+   GLShader_overBright( GLShaderManager *manager );
+};
+
 // This is just a copy of the GLShader_generic, but with a special
 // define for RmlUI transforms. It probably has a lot of unnecessary
 // code that could be pruned.
@@ -2903,6 +2911,7 @@ std::string GetShaderPath();

 extern ShaderKind shaderKind;

+extern GLShader_overBright                      *gl_overBrightShader;
 extern GLShader_generic2D                       *gl_generic2DShader;
 extern GLShader_generic                         *gl_genericShader;
 extern GLShader_lightMapping                    *gl_lightMappingShader;


diff --git a/src/engine/renderer/glsl_source/overBright_fp.glsl b/src/engine/renderer/glsl_source/overBright_fp.glsl
new file mode 100644
index 000000000..739f3c733
--- /dev/null
+++ b/src/engine/renderer/glsl_source/overBright_fp.glsl
@@ -0,0 +1,8 @@
+DECLARE_OUTPUT(vec4)
+
+uniform float u_LightFactor;
+
+void main()
+{
+   outputColor = vec4( u_LightFactor, u_LightFactor, u_LightFactor, 1 );
+}


diff --git a/src/engine/renderer/glsl_source/overBright_vp.glsl b/src/engine/renderer/glsl_source/overBright_vp.glsl
new file mode 100644
index 000000000..b13f0ada0
--- /dev/null
+++ b/src/engine/renderer/glsl_source/overBright_vp.glsl
@@ -0,0 +1,3 @@
+void main ()
+{
+}


diff --git a/src/engine/renderer/shaders.cpp b/src/engine/renderer/shaders.cpp
index 35f6d3a97..17ad5a2e1 100644
--- a/src/engine/renderer/shaders.cpp
+++ b/src/engine/renderer/shaders.cpp
@@ -47,6 +47,8 @@
 #include "liquid_vp.glsl.h"
 #include "motionblur_fp.glsl.h"
 #include "motionblur_vp.glsl.h"
+#include "overBright_fp.glsl.h"
+#include "overBright_vp.glsl.h"
 #include "portal_fp.glsl.h"
 #include "portal_vp.glsl.h"
 #include "reflection_CB_fp.glsl.h"
@@ -101,6 +103,8 @@ std::unordered_map<std::string, std::string> shadermap({
    { "glsl/liquid_vp.glsl", std::string(reinterpret_cast<const char*>(liquid_vp_glsl), sizeof(liquid_vp_glsl)) },
    { "glsl/motionblur_fp.glsl", std::string(reinterpret_cast<const char*>(motionblur_fp_glsl), sizeof(motionblur_fp_glsl)) },
    { "glsl/motionblur_vp.glsl", std::string(reinterpret_cast<const char*>(motionblur_vp_glsl), sizeof(motionblur_vp_glsl)) },
+   { "glsl/overBright_fp.glsl", std::string(reinterpret_cast<const char*>(overBright_fp_glsl), sizeof(overBright_fp_glsl)) },
+   { "glsl/overBright_vp.glsl", std::string(reinterpret_cast<const char*>(overBright_vp_glsl), sizeof(overBright_vp_glsl)) },
    { "glsl/portal_fp.glsl", std::string(reinterpret_cast<const char*>(portal_fp_glsl), sizeof(portal_fp_glsl)) },
    { "glsl/portal_vp.glsl", std::string(reinterpret_cast<const char*>(portal_vp_glsl), sizeof(portal_vp_glsl)) },
    { "glsl/reflection_CB_fp.glsl", std::string(reinterpret_cast<const char*>(reflection_CB_fp_glsl), sizeof(reflection_CB_fp_glsl)) },


diff --git a/src/engine/renderer/tr_shade.cpp b/src/engine/renderer/tr_shade.cpp
index 6975277b3..d46ae5246 100644
--- a/src/engine/renderer/tr_shade.cpp
+++ b/src/engine/renderer/tr_shade.cpp
@@ -58,6 +58,9 @@ static void GLSL_InitGPUShadersOrError()

    gl_shaderManager.GenerateBuiltinHeaders();

+   // overBright light multiplication
+   gl_shaderManager.load( gl_overBrightShader );
+
    // single texture rendering
    gl_shaderManager.load( gl_generic2DShader );
    gl_shaderManager.load( gl_genericShader );
@@ -2353,6 +2356,17 @@ static void Render_liquid( shaderStage_t *pStage )
    GL_CheckErrors();
 }

+static void Render_overBright()
+{
+   GL_State( GLS_SRCBLEND_ONE | GLS_DSTBLEND_ONE );
+   gl_overBrightShader->BindProgram( 0 );
+   gl_overBrightShader->SetUniform_LightFactor( 1 );
+
+   Tess_DrawElements();
+
+   GL_CheckErrors();
+}
+
 static void Render_fog()
 {
    fog_t  *fog;
@@ -2887,6 +2901,8 @@ void Tess_StageIteratorGeneric()
        }
    }

+   Render_overBright();
+
    if ( !r_noFog->integer && tess.fogNum >= 1 && tess.surfaceShader->fogPass != fogPass_t::FP_NONE )
    {
        Render_fog();