add entity shader

res/shaders/entity.glslf

@@ -0,0 +1,24 @@
+in vec4 a_color;
+in vec2 a_texCoord;
+in float a_distance;
+in vec3 a_dir;
+out vec4 f_color;
+
+uniform sampler2D u_texture0;
+uniform samplerCube u_cubemap;
+uniform vec3 u_fogColor;
+uniform float u_fogFactor;
+uniform float u_fogCurve;
+
+void main() {
+    vec3 fogColor = texture(u_cubemap, a_dir).rgb;
+    vec4 tex_color = texture(u_texture0, a_texCoord);
+    float depth = (a_distance/256.0);
+    float alpha = a_color.a * tex_color.a;
+    // anyway it's any alpha-test alternative required
+    if (alpha < 0.3f)
+        discard;
+    f_color = mix(a_color * tex_color, vec4(fogColor,1.0), 
+              min(1.0, pow(depth*u_fogFactor, u_fogCurve)));
+    f_color.a = alpha;
+}