Moved spherical coordinates conversion to shader.

Co-Authored-By: Emil Wallberg <49481622+EmilWallberg@users.noreply.github.com>

modules/blackhole/rendering/viewport.cpp

@@ -35,18 +35,15 @@ namespace openspace {
 
         std::vector<float> data(screenSize.x * screenSize.y * 2, 0.0f);
 
-        float z = -1.0f; 
+      
         for (int i = 0; i < screenSize.y; i++) {
             float y = (i - screenSize.y / 2) * stepSize;
             for (int j = 0; j < screenSize.x; j++) {
                 float x = (j - screenSize.x / 2) * stepSize;
-
-                float theta = atan2(sqrt(x * x + y * y) , z);
-                float phi = atan2(y, x);
-
                 int index = (screenSize.x * i + j) * 2;
-                data[index] = phi;
-                data[index + 1] = theta;
+
+                data[index] = x;
+                data[index + 1] = y;
             }
         }
         updateViewGridTexture(data, screenSize);

modules/blackhole/shaders/blackhole_fs.glsl

@@ -5,6 +5,7 @@ uniform sampler2D enviromentTexture;
 uniform sampler2D viewGrid;
 
 const float PI = 3.1415926535897932384626433832795f;
+const float VIEWGRIDZ = -1.0f;
 
 vec2 sphereToUV(vec2 sphereCoords){
     float u = sphereCoords.x / (2.0f * PI) + 0.5f;
@@ -13,10 +14,28 @@ vec2 sphereToUV(vec2 sphereCoords){
     return vec2(u, v);
 }
 
+float atan2(float a, float b){
+    if (b != 0.0f) return atan(a, b);
+    if (a > 0.0f) return PI / 2.0f;
+    if (a < 0.0f) return -PI / 2.0f;
+        
+    return 0.0f;
+}
+
+vec2 cartisianToSphereical(vec2 cartisian) {
+    float theta = atan(sqrt(cartisian.x * cartisian.x + cartisian.y * cartisian.y) , VIEWGRIDZ);
+    float phi = atan2(cartisian.y, cartisian.x);
+
+    return vec2(phi, theta);
+}
+
 Fragment getFragment() {
     Fragment frag;
-    vec2 sphereCoords = texture(viewGrid, TexCoord).rg;
-    vec4 texColor = texture(enviromentTexture, sphereToUV(sphereCoords));
+    vec2 cartisianCoords = texture(viewGrid, TexCoord).xy;
+    vec2 sphereicaleCoords = cartisianToSphereical(cartisianCoords);
+    vec2 uv = sphereToUV(sphereicaleCoords);
+
+    vec4 texColor = texture(enviromentTexture, uv);
     
     frag.color = texColor;
     return frag;