From 92a3ca3a9c80f9ea4e5b989ac1e7cdc0f1b603d5 Mon Sep 17 00:00:00 2001
From: bloeys <bloeys@outlook.com>
Date: Sun, 7 Nov 2021 04:47:53 +0400
Subject: [PATCH] LookAt func

---
 gglm/transform.go | 22 +++++++++++++++++++++-
 main.go           |  7 +++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gglm/transform.go b/gglm/transform.go
index 2045340..bdadc33 100755
--- a/gglm/transform.go
+++ b/gglm/transform.go
@@ -1,6 +1,8 @@
 package gglm
 
-import "fmt"
+import (
+	"fmt"
+)
 
 var _ Mat = &TrMat{}
 var _ fmt.Stringer = &TrMat{}
@@ -96,6 +98,24 @@ func NewRotMat(q *Quat) *TrMat {
 	}
 }
 
+func LookAt(pos, targetPos, worldUp *Vec3) *TrMat {
+
+	forward := SubVec3(targetPos, pos).Normalize()
+	right := Cross(worldUp, forward).Normalize()
+	up := Cross(forward, right)
+
+	return &TrMat{
+		Mat4: Mat4{
+			Data: [16]float32{
+				right.Data[0], right.Data[1], right.Data[2], -DotVec3(pos, right),
+				up.Data[0], up.Data[1], up.Data[2], -DotVec3(pos, up),
+				forward.Data[0], forward.Data[1], forward.Data[2], -DotVec3(pos, forward),
+				0, 0, 0, 1,
+			},
+		},
+	}
+}
+
 func NewTrMatId() *TrMat {
 	return &TrMat{
 		Mat4: *NewMat4Id(),
diff --git a/main.go b/main.go
index dadeae7..499d510 100755
--- a/main.go
+++ b/main.go
@@ -164,4 +164,11 @@ func main() {
 	q1 := gglm.NewQuatEuler(gglm.NewVec3(180, 0, 0).AsRad())
 	q2 := gglm.NewQuatEuler(gglm.NewVec3(0, 180, 0).AsRad())
 	println(gglm.AngleQuat(q1, q2) * gglm.Rad2Deg)
+
+	//LookAt
+	camPos := gglm.NewVec3(0, 0, 3)
+	worldUp := gglm.NewVec3(0, 1, 0)
+	targetPos := gglm.NewVec3(0, 0, 0)
+	viewMat := gglm.LookAt(camPos, targetPos, worldUp)
+	println(viewMat.String())
 }