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# Objective A very common way to organize a first-person view is to split it into two kinds of models: - The *view model* is the model that represents the player's body. - The *world model* is everything else. The reason for this distinction is that these two models should be rendered with different FOVs. The view model is typically designed and animated with a very specific FOV in mind, so it is generally *fixed* and cannot be changed by a player. The world model, on the other hand, should be able to change its FOV to accommodate the player's preferences for the following reasons: - *Accessibility*: How prone is the player to motion sickness? A wider FOV can help. - *Tactical preference*: Does the player want to see more of the battlefield? Or have a more zoomed-in view for precision aiming? - *Physical considerations*: How well does the in-game FOV match the player's real-world FOV? Are they sitting in front of a monitor or playing on a TV in the living room? How big is the screen? ## Solution I've added an example implementing the described setup as follows. The `Player` is an entity holding two cameras, one for each model. The view model camera has a fixed FOV of 70 degrees, while the world model camera has a variable FOV that can be changed by the player. I use different `RenderLayers` to select what to render. - The world model camera has no explicit `RenderLayers` component, so it uses the layer 0. All static objects in the scene are also on layer 0 for the same reason. - The view model camera has a `RenderLayers` component with layer 1, so it only renders objects explicitly assigned to layer 1. The arm of the player is one such object. The order of the view model camera is additionally bumped to 1 to ensure it renders on top of the world model. - The light source in the scene must illuminate both the view model and the world model, so it is assigned to both layers 0 and 1. To better see the effect, the player can move the camera by dragging their mouse and change the world model's FOV with the arrow keys. The arrow up key maps to "decrease FOV" and the arrow down key maps to "increase FOV". This sounds backwards on paper, but is more intuitive when actually changing the FOV in-game since a decrease in FOV looks like a zoom-in. I intentionally do not allow changing the view model's FOV even though it would be illustrative because that would be an anti-pattern and bloat the code a bit. The example is called `first_person_view_model` and not just `first_person` because I want to highlight that this is not a simple flycam, but actually renders the player. ## Testing Default FOV: <img width="1392" alt="image" src="https://github.com/bevyengine/bevy/assets/9047632/8c2e804f-fac2-48c7-8a22-d85af999dfb2"> Decreased FOV: <img width="1392" alt="image" src="https://github.com/bevyengine/bevy/assets/9047632/1733b3e5-f583-4214-a454-3554e3cbd066"> Increased FOV: <img width="1392" alt="image" src="https://github.com/bevyengine/bevy/assets/9047632/0b0640e6-5743-46f6-a79a-7181ba9678e8"> Note that the white bar on the right represents the player's arm, which is more obvious in-game because you can move the camera around. The box on top is there to make sure that the view model is receiving shadows. I tested only on macOS. --- ## Changelog I don't think new examples go in here, do they? ## Caveat The solution used here was implemented with help by @robtfm on [Discord](https://discord.com/channels/691052431525675048/866787577687310356/1241019224491561000): > shadow maps are specific to lights, not to layers > if you want shadows from some meshes that are not visible, you could have light on layer 1+2, meshes on layer 2, camera on layer 1 (for example) > but this might change in future, it's not exactly an intended feature In other words, the example code as-is is not guaranteed to work in the future. I want to bring this up because the use-case presented here is extremely common in first-person games and important for accessibility. It would be good to have a blessed and easy way of how to achieve it. I'm also not happy about how I get the `perspective` variable in `change_fov`. Very open to suggestions :) ## Related issues - Addresses parts of #12658 - Addresses parts of #12588 --------- Co-authored-by: Pascal Hertleif <killercup@gmail.com> |
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| .. | ||
| 2d_top_down_camera.rs | ||
| first_person_view_model.rs | ||