First attempt at rendering placefile icons, does not work yet

scwx-qt/gl/geo_texture2d.vert

@@ -0,0 +1,42 @@
+#version 330 core
+
+#define DEGREES_MAX   360.0f
+#define LATITUDE_MAX  85.051128779806604f
+#define LONGITUDE_MAX 180.0f
+#define PI            3.1415926535897932384626433f
+#define RAD2DEG       57.295779513082320876798156332941f
+
+layout (location = 0) in vec2  aLatLong;
+layout (location = 1) in vec2  aXYOffset;
+layout (location = 2) in vec2  aTexCoord;
+layout (location = 3) in vec4  aModulate;
+layout (location = 4) in float aAngle;
+
+uniform mat4 uMVPMatrix;
+uniform mat4 uMapMatrix;
+uniform vec2 uMapScreenCoord;
+
+smooth out vec2 texCoord;
+flat   out vec4 modulate;
+
+vec2 latLngToScreenCoordinate(in vec2 latLng)
+{
+   vec2 p;
+   latLng.x = clamp(latLng.x, -LATITUDE_MAX, LATITUDE_MAX);
+   p.xy     = vec2(LONGITUDE_MAX + latLng.y,
+                   -(LONGITUDE_MAX - RAD2DEG * log(tan(PI / 4 + latLng.x * PI / DEGREES_MAX))));
+   return p;
+}
+
+void main()
+{
+   // Pass the texture coordinate and color modulate to the fragment shader
+   texCoord = aTexCoord;
+   modulate = aModulate;
+
+   vec2 p = latLngToScreenCoordinate(aLatLong) - uMapScreenCoord;
+
+   // Transform the position to screen coordinates
+   gl_Position = uMapMatrix * vec4(p, 0.0f, 1.0f) -
+                 uMVPMatrix * vec4(aXYOffset, 0.0f, 0.0f);
+}