Add lambert lighting to the splatting shader to make it look less flat

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@10435 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/shaders/splatting.frag

@@ -6,6 +6,8 @@ uniform sampler2D tex_detail1;
 uniform sampler2D tex_detail2;
 uniform sampler2D tex_detail3;
 uniform sampler2D tex_detail4;
+varying vec3 normal;
+varying vec3 lightdir2;
 
 void main()
 {
@@ -15,10 +17,11 @@ void main()
     vec4 detail2 = texture2D(tex_detail2, gl_TexCoord[1].st);
     vec4 detail3 = texture2D(tex_detail3, gl_TexCoord[1].st);
     vec4 detail4 = texture2D(tex_detail4, gl_TexCoord[1].st);
-
-    gl_FragColor = layout.r * detail0 +
-                   layout.g * detail1 +
-                   layout.b * detail2 +
-                   (1.0 - layout.r - layout.g - layout.b) * detail3 +
-                   (1.0 - layout.a) * detail4;
+    
+    gl_FragColor = (layout.r * detail0 +
+                    layout.g * detail1 +
+                    layout.b * detail2 +
+                    (1.0 - layout.r - layout.g - layout.b) * detail3 +
+                    (1.0 - layout.a) * detail4)
+                    * min(1.0, 0.2 + 1.5*dot(lightdir2, normal)); // 0.2 is the ambient light. *1.5 is from trial are error to make it look nice :)
 }

data/shaders/splatting.vert

@@ -1,7 +1,15 @@
+varying vec3 normal;
+
+varying vec3 lightdir2;
+uniform vec3 lightdir;
 
 void main()
 {
 	gl_TexCoord[0] = gl_MultiTexCoord0;
     gl_TexCoord[1] = gl_MultiTexCoord1;
-    gl_Position = ftransform(); 
+    gl_Position = ftransform();
+    
+    //normal = normalize(gl_NormalMatrix * gl_Normal);
+    normal = normalize(gl_Normal);
+    lightdir2 = normalize(lightdir);
 }

src/graphics/material.cpp

@@ -99,6 +99,11 @@ public:
         // Irrlicht knows this is actually a GLint and makes the conversion
         int tex_detail3 = 4;
         services->setPixelShaderConstant("tex_detail3", (float*)&tex_detail3, 1);
+        
+        // TODO: check the position of the sun
+        core::vector3df lightdir(-0.1f, 0.1f, 0.0f);
+        lightdir.normalize();
+        services->setVertexShaderConstant("lightdir", &lightdir.X, 3);
     }
 };