Cycles: add Equiangular Cubemap Face camera projection

This can be used for example for VR video formats that use this projection
instead of perspective projection for cubemap faces.

Differential Revision: https://developer.blender.org/D13525

intern/cycles/blender/addon/properties.py

@@ -60,13 +60,14 @@ enum_filter_types = (
 )
 
 enum_panorama_types = (
-    ('EQUIRECTANGULAR', "Equirectangular", "Render the scene with a spherical camera, also known as Lat Long panorama"),
-    ('FISHEYE_EQUIDISTANT', "Fisheye Equidistant", "Ideal for fulldomes, ignore the sensor dimensions"),
+    ('EQUIRECTANGULAR', "Equirectangular", "Spherical camera for environment maps, also known as Lat Long panorama", 0),
+    ('EQUIANGULAR_CUBEMAP_FACE', "Equiangular Cubemap Face", "Single face of an equiangular cubemap", 5),
+    ('MIRRORBALL', "Mirror Ball", "Mirror ball mapping for environment maps", 3),
+    ('FISHEYE_EQUIDISTANT', "Fisheye Equidistant", "Ideal for fulldomes, ignore the sensor dimensions", 1),
     ('FISHEYE_EQUISOLID', "Fisheye Equisolid",
-                          "Similar to most fisheye modern lens, takes sensor dimensions into consideration"),
-    ('MIRRORBALL', "Mirror Ball", "Uses the mirror ball mapping"),
+                          "Similar to most fisheye modern lens, takes sensor dimensions into consideration", 2),
     ('FISHEYE_LENS_POLYNOMIAL', "Fisheye Lens Polynomial",
-     "Defines the lens projection as polynomial to allow real world camera lenses to be mimicked"),
+     "Defines the lens projection as polynomial to allow real world camera lenses to be mimicked", 4),
 )
 
 enum_curve_shape = (

intern/cycles/kernel/camera/projection.h

@@ -201,11 +201,35 @@ ccl_device float2 direction_to_mirrorball(float3 dir)
   return make_float2(u, v);
 }
 
+/* Single face of a equiangular cube map projection as described in
+   https://blog.google/products/google-ar-vr/bringing-pixels-front-and-center-vr-video/ */
+ccl_device float3 equiangular_cubemap_face_to_direction(float u, float v)
+{
+  u = (1.0f - u);
+
+  u = tanf(u * M_PI_2_F - M_PI_4_F);
+  v = tanf(v * M_PI_2_F - M_PI_4_F);
+
+  return make_float3(1.0f, u, v);
+}
+
+ccl_device float2 direction_to_equiangular_cubemap_face(float3 dir)
+{
+  float u = atan2f(dir.y, dir.x) * 2.0f / M_PI_F + 0.5f;
+  float v = atan2f(dir.z, dir.x) * 2.0f / M_PI_F + 0.5f;
+
+  u = 1.0f - u;
+
+  return make_float2(u, v);
+}
+
 ccl_device_inline float3 panorama_to_direction(ccl_constant KernelCamera *cam, float u, float v)
 {
   switch (cam->panorama_type) {
     case PANORAMA_EQUIRECTANGULAR:
       return equirectangular_range_to_direction(u, v, cam->equirectangular_range);
+    case PANORAMA_EQUIANGULAR_CUBEMAP_FACE:
+      return equiangular_cubemap_face_to_direction(u, v);
     case PANORAMA_MIRRORBALL:
       return mirrorball_to_direction(u, v);
     case PANORAMA_FISHEYE_EQUIDISTANT:
@@ -230,6 +254,8 @@ ccl_device_inline float2 direction_to_panorama(ccl_constant KernelCamera *cam, f
   switch (cam->panorama_type) {
     case PANORAMA_EQUIRECTANGULAR:
       return direction_to_equirectangular_range(dir, cam->equirectangular_range);
+    case PANORAMA_EQUIANGULAR_CUBEMAP_FACE:
+      return direction_to_equiangular_cubemap_face(dir);
     case PANORAMA_MIRRORBALL:
       return direction_to_mirrorball(dir);
     case PANORAMA_FISHEYE_EQUIDISTANT:

intern/cycles/kernel/types.h

@@ -490,6 +490,7 @@ enum PanoramaType {
   PANORAMA_FISHEYE_EQUISOLID = 2,
   PANORAMA_MIRRORBALL = 3,
   PANORAMA_FISHEYE_LENS_POLYNOMIAL = 4,
+  PANORAMA_EQUIANGULAR_CUBEMAP_FACE = 5,
 
   PANORAMA_NUM_TYPES,
 };

intern/cycles/scene/camera.cpp

@@ -84,6 +84,7 @@ NODE_DEFINE(Camera)
 
   static NodeEnum panorama_type_enum;
   panorama_type_enum.insert("equirectangular", PANORAMA_EQUIRECTANGULAR);
+  panorama_type_enum.insert("equiangular_cubemap_face", PANORAMA_EQUIANGULAR_CUBEMAP_FACE);
   panorama_type_enum.insert("mirrorball", PANORAMA_MIRRORBALL);
   panorama_type_enum.insert("fisheye_equidistant", PANORAMA_FISHEYE_EQUIDISTANT);
   panorama_type_enum.insert("fisheye_equisolid", PANORAMA_FISHEYE_EQUISOLID);