From f9113b7eb6ee0e7a6222bd6fbc7e39cb9c6fc395 Mon Sep 17 00:00:00 2001
From: Damian Trebilco <Damian_Trebilco>
Date: Fri, 28 Oct 2022 14:30:18 +0200
Subject: 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 | 11 ++++++-----
 intern/cycles/kernel/camera/projection.h  | 26 ++++++++++++++++++++++++++
 intern/cycles/kernel/types.h              |  1 +
 intern/cycles/scene/camera.cpp            |  1 +
 4 files changed, 34 insertions(+), 5 deletions(-)

(limited to 'intern')

diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index 94e2d840b28..f5cd88f6b6a 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/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 = (
diff --git a/intern/cycles/kernel/camera/projection.h b/intern/cycles/kernel/camera/projection.h
index c9fe3a6c7fb..1d16aa35abe 100644
--- a/intern/cycles/kernel/camera/projection.h
+++ b/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:
diff --git a/intern/cycles/kernel/types.h b/intern/cycles/kernel/types.h
index 8f7cfd19169..24c5a6a4540 100644
--- a/intern/cycles/kernel/types.h
+++ b/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,
 };
diff --git a/intern/cycles/scene/camera.cpp b/intern/cycles/scene/camera.cpp
index 240e5d9c128..255dd320ec7 100644
--- a/intern/cycles/scene/camera.cpp
+++ b/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);
-- 
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