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docs/lectures/graphics/07_camera.md

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+# Camera Essentials
+
+There are two types of camera:
+
+1. A model-viewer camera
+2. A fly-through camera
+
+A camera involves
+
+1. A position in 3D space
+2. A forward direction
+3. A right direction
+4. An up direction
+
+Calculating a camera direction can be achieved using Euler angles, **pitch**, **yaw** and **roll** .
+
+- Pitch rotates the camera on the x axis
+  - Think of a plane pointing its nose to the floor or to the sky
+- Yaw rotates the camera on the y axis
+  - Think a plane moving the nose left to right keeping the wings parallel with the ground
+- Roll rotates the camera on the z axis
+  - Think tilting the plane’s wings left and right, but not changing the direction of the nose
+
+#### Model-Viewer Camera
+
+This is a camera that can rotate around the model in a sphere.
+
+![1648476699.png](img/1648476699.png)
+
+Changing the pitch of the camera makes the camera move upwards and point downwards, here the camera moves around the sphere where the direction is always towards the model
+
+![1648476784.png](img/1648476784.png)
+
+The camera can also move back and forwards, making the sphere bigger or smaller.
+
+![1648476819.png](img/1648476819.png)
+
+$$
+\begin{aligned}
+p_x = &\cos\theta * \cos\alpha \\
+p_y = &\sin\alpha \\
+p_z = &\sin\theta * \cos\alpha
+\end{aligned}
+$$
+
+#### Fly-Through Camera
+
+The camera has a position in world space and a focus direction `front`, which can be focused on the model or not.
+
+We can move this kind of camera, forward, backward, left and right along with pitch, roll and yaw.
+
+The camera is at the center of the sphere, and the model moves around the edge of the sphere.
+
+A unit vector points from the camera to the model as the front direction of the camera
+
+We can move the camera forwards and backwards by
+
+```c
+pos += front //forwards
+pos -= front //backwards
+
+pos += right //move right
+pos -= right //move left
+```