Add FRUSTUM camera mode, allowing tilted frustums

This new camera mode makes it easy to create tilted frustums for mirror
or portal effects.

This work was kindly sponsored by IMVU.

2 files changed, 9 insertions, 0 deletions

diff --git a/core/math/camera_matrix.cpp b/core/math/camera_matrix.cpp
index caf08c7379..f615cc8c65 100644
--- a/core/math/camera_matrix.cpp
+++ b/core/math/camera_matrix.cpp
@@ -210,6 +210,14 @@ void CameraMatrix::set_frustum(real_t p_left, real_t p_right, real_t p_bottom, r
 	te[15] = 0;
 }
 
+void CameraMatrix::set_frustum(real_t p_size, real_t p_aspect, Vector2 p_offset, real_t p_near, real_t p_far, bool p_flip_fov) {
+	if (!p_flip_fov) {
+		p_size *= p_aspect;
+	}
+
+	set_frustum(-p_size / 2 + p_offset.x, +p_size / 2 + p_offset.x, -p_size / p_aspect / 2 + p_offset.y, +p_size / p_aspect / 2 + p_offset.y, p_near, p_far);
+}
+
 real_t CameraMatrix::get_z_far() const {
 
 	const real_t *matrix = (const real_t *)this->matrix;
diff --git a/core/math/camera_matrix.h b/core/math/camera_matrix.h
index 015588a8cb..3bcf48f5da 100644
--- a/core/math/camera_matrix.h
+++ b/core/math/camera_matrix.h
@@ -61,6 +61,7 @@ struct CameraMatrix {
 	void set_orthogonal(real_t p_left, real_t p_right, real_t p_bottom, real_t p_top, real_t p_znear, real_t p_zfar);
 	void set_orthogonal(real_t p_size, real_t p_aspect, real_t p_znear, real_t p_zfar, bool p_flip_fov = false);
 	void set_frustum(real_t p_left, real_t p_right, real_t p_bottom, real_t p_top, real_t p_near, real_t p_far);
+	void set_frustum(real_t p_size, real_t p_aspect, Vector2 p_offset, real_t p_near, real_t p_far, bool p_flip_fov = false);
 
 	static real_t get_fovy(real_t p_fovx, real_t p_aspect) {