Added code for non-euclidean terrain transitions

- This is used for a music video currently in production using the 
shaderpack

Author: BruceKnowsHow

shaders/gbuffers_main.glsl

@@ -219,6 +219,7 @@ float GetSpecularity(vec2 coord) {
 
 
 #include "/../shaders/lib/Fragment/TerrainParallax.fsh"
+#include "/../shaders/lib/Misc/Euclid.glsl"
 
 
 #if defined gbuffers_water
@@ -238,7 +239,6 @@ void main() {
 	vec3  normal      = GetNormal(coord);
 	float specularity = GetSpecularity(coord);
 
-	
 #if !defined gbuffers_water
 	float encodedMaterialIDs = EncodeMaterialIDs(materialIDs, vec4(0.0, 0.0, 0.0, 0.0));
 

shaders/lib/Misc/Euclid.glsl

@@ -0,0 +1,40 @@
+#if !defined EUCLID_GLSL
+#define EUCLID_GLSL
+
+float DistanceToPlane(vec3 point, vec3 p0, vec3 p1, vec3 p2) {
+	vec3   normal = normalize(cross(p1 - p0, p2 - p0));
+	return dot(normal, point) - dot(normal, p0);
+}
+
+float DistanceToPlane(vec3 point, vec3 p1, vec3 p2) {
+	vec3   normal = normalize(cross(p1, p2));
+	return dot(normal, point);
+}
+
+bool IsInsideFrustum(vec3 pos, vec3 center, float horizontalSpan, float verticalSpan) {
+	vec3 topLeft  = center + vec3(0.0,  verticalSpan, -horizontalSpan );
+	vec3 topRight = center + vec3(0.0,  verticalSpan,  horizontalSpan );
+	vec3 botLeft  = center + vec3(0.0, -verticalSpan, -horizontalSpan );
+	vec3 botRight = center + vec3(0.0, -verticalSpan,  horizontalSpan );
+	
+	vec3 camPos = cameraPosition + vec3(1000*0,0,0) + gbufferModelViewInverse[3].xyz;
+	
+	bool b1 = DistanceToPlane(pos, camPos, topLeft, topRight) < 0.0;
+	bool b2 = DistanceToPlane(pos, camPos, topRight, botRight) < 0.0;
+	bool b3 = DistanceToPlane(pos, camPos, botRight, botLeft) < 0.0;
+	bool b4 = DistanceToPlane(pos, camPos, botLeft, topLeft) < 0.0;
+	
+	if (camPos.x < center.x)
+		return !(b1||b2||b3||b4);
+	else
+		return !(b1&&b2&&b3&&b4);
+}
+
+/* Example:
+if (IsInsideFrustum(position[1]+cameraPosition+gbufferModelViewInverse[3].xyz, vec3(1177-1000,81.0,5.5), 0.5, 1.0)) {
+    diffuse.rgb*= 0.0;
+    diffuse.a *= 0.0;
+}
+*/
+
+#endif