1 files changed, 125 insertions, 0 deletions
diff --git a/ground.frag b/ground.frag
new file mode 100644
index 0000000..1938364
--- /dev/null
+++ b/ground.frag
@@ -0,0 +1,125 @@
+void main()
+{
+	gl_FragColor = vec4(1,0,0,0);
+}
+
+#if 0
+varying vec3 light_surf;
+varying vec3 eye_surf;
+varying vec3 tangent_surf;
+varying vec2 texcoord;
+uniform sampler2D normal_sampler;
+uniform sampler2D heightmap_sampler;
+uniform float F0, ni;
+
+float schlick_fresnel(float n_dot_l)
+{
+	return F0 + (1 - F0) * pow(1 - n_dot_l, 5);
+}
+
+/* This returns garbage compared to Schlick. */
+float fresnel(float v_dot_h)
+{
+	float c = v_dot_h; /* cos theta, v . h or l . h */
+	float g = sqrt(ni * ni + c * c - 1);
+	float gmc = g - c;
+	float gpc = g + c;
+	float c_gpc_m_1_squared = (c * gpc - 1) * (c * gpc - 1);
+	float c_gmc_p_1_squared = (c * gmc + 1) * (c * gmc + 1);
+
+	return gmc*gmc / (2 * gpc*gpc) * (1 + c_gmc_p_1_squared /
+					  c_gpc_m_1_squared);
+}
+
+void main()
+{
+	const vec4 material_color = vec4(0.7, 0.5, 0.3, 0.0);
+	vec3 l = normalize(light_surf);
+	vec3 v = normalize(eye_surf);
+	vec3 h = normalize(l + v);
+	vec3 t = normalize(tangent_surf);
+	vec3 n = texture2D(normal_sampler, texcoord).xyz * 2 - 1;
+	/* Hack: Reduce the significance of our normal map, which otherwise
+	 * looks incongruous with the straight edges.
+	 */
+	n = normalize(n + vec3(0,0,1));
+	float n_dot_l = dot(n, l);
+	float n_dot_v = dot(n, v);
+	float n_dot_h = dot(n, h);
+	float v_dot_h = dot(v, h);
+	float s = .7;
+	float d = 1 - s;
+	float Ii = 0.9; /*intensity of incoming light */
+	float Iia = .1 * Ii; /*intensity of ambient light */
+
+	float cos2_alpha = n_dot_h * n_dot_h;
+	float tan2_alpha = (1 - cos2_alpha) / cos2_alpha;
+	float Rs;
+	float D;
+
+	/* Aniso BRDF from Ward's "Measuring and Modeling
+	 * Anisotropic Reflection".
+	 */
+
+	/* brushed metal */
+	float ward_n = .037;
+	float ward_m = .063;
+
+	/* Make phi be the angle between the projections of
+	 * the tangent and half-angle vectors onto the
+	 * surface plane (z=0).  Doing it right would involve
+	 * projecting onto the plane defined by n.
+	 */
+	float cos_phi = dot(normalize(t.xy), normalize(h.xy));
+
+	float cos2_phi_over_m2 = ((cos_phi * cos_phi) / (ward_m * ward_m));
+	float sin2_phi_over_n2 = ((1 - cos_phi * cos_phi) / (ward_n * ward_n));
+#if 1
+	D = exp(-tan2_alpha * (cos2_phi_over_m2 + sin2_phi_over_n2));
+#else
+	/* Ward's "computationally convenient" equation.
+	 * Doesn't work.
+	 */
+	D = exp(-2 * (cos2_phi_over_m2 +
+		      sin2_phi_over_n2) /
+		(1 + n_dot_h));
+#endif
+	Rs = 2 * schlick_fresnel(n_dot_l) * D /
+	  sqrt(n_dot_l * n_dot_v) / (ward_m * ward_n);
+
+	Rs *= step(0, n_dot_l);
+	Rs *= step(0, n_dot_v);
+
+	float Rd = (1 - F0) * 2;
+	/* Ambient occlusion factor -- sample the height map we
+	 * used to generate the normal map, and reduce intensity in
+	 * the valleys.
+	 */
+	float heightmap = texture2D(heightmap_sampler, texcoord).x;
+	float Ra = Rd * (.8 + .2 * heightmap);
+
+	gl_FragColor = n_dot_l * step(0, n_dot_l) *
+	  vec4(material_color.xyz *
+	       (Rd * d + Rs * s),
+	       material_color.w) +
+	  Iia * Ra * material_color.xyzw;
+
+	/* Debugging scalars -- Map [0,1] to [0.5,1] to catch negative
+	 * values.  Multiply by the step function to catch when
+	 * the scalar won't come into play because Rs == 0.
+	 */
+#if 0
+	gl_FragColor = vec4(vec3(F0 / 2 + .5), 1);
+#endif
+/* Normal visualization */
+/*
+vec3 temp = vec3((normal.x + 1) / 2,
+		  (normal.y + 1) / 2,
+		  (normal.z + 1) / 2);
+gl_FragColor = vec4(temp.xyz, 0);
+*/
+/*
+	gl_FragColor = texture2D(normal_sampler, texcoord);
+*/
+}
+#endif
+\ No newline at end of file