Add the ability to look-at in model-space.

This is a much simpler attempt to solve the same problem as #76060, but without breaking any compatibility.

* Adds a description of what model space is in the Vector3 enums (MODEL_* constants). This has the proper axes laid out for imported 3D assets.
* Adds the option to `look_at` using model_space, which uses Vector3.MODEL_FRONT as forward vector.

The attempt of this PR is to still break the assumption that there is a single direction of forward (which is not the case in Godot)
and make it easier to understand where 3D models are facing, as well as orienting them via look_at.

1 files changed, 5 insertions, 2 deletions

diff --git a/core/math/basis.cpp b/core/math/basis.cpp
index bfd902c7e2..1481dbc32e 100644
--- a/core/math/basis.cpp
+++ b/core/math/basis.cpp
@@ -1016,12 +1016,15 @@ void Basis::rotate_sh(real_t *p_values) {
 	p_values[8] = d4 * s_scale_dst4;
 }
 
-Basis Basis::looking_at(const Vector3 &p_target, const Vector3 &p_up) {
+Basis Basis::looking_at(const Vector3 &p_target, const Vector3 &p_up, bool p_use_model_front) {
 #ifdef MATH_CHECKS
 	ERR_FAIL_COND_V_MSG(p_target.is_zero_approx(), Basis(), "The target vector can't be zero.");
 	ERR_FAIL_COND_V_MSG(p_up.is_zero_approx(), Basis(), "The up vector can't be zero.");
 #endif
-	Vector3 v_z = -p_target.normalized();
+	Vector3 v_z = p_target.normalized();
+	if (!p_use_model_front) {
+		v_z = -v_z;
+	}
 	Vector3 v_x = p_up.cross(v_z);
 #ifdef MATH_CHECKS
 	ERR_FAIL_COND_V_MSG(v_x.is_zero_approx(), Basis(), "The target vector and up vector can't be parallel to each other.");