--- /dev/null
+#define FOV 0.873 /* about 50 deg */
+
+varying vec3 v_rorg, v_rdir;
+
+void main()
+{
+ gl_Position = gl_Vertex;
+
+ float dist = 1.0 / tan(FOV / 2.0);
+ vec3 dir = vec3(gl_MultiTexCoord0.xy * 2.0 - 1.0, dist);
+ v_rdir = gl_NormalMatrix * dir;
+ v_rorg = (gl_ModelViewMatrix * vec4(0.0, 0.0, 0.0, 1.0)).xyz;
+}