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281 lines
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.. _doc_resolution_scaling:
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Resolution scaling
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==================
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.. Images on this page were generated using the project below:
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.. https://github.com/Calinou/godot-antialiasing-comparison
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Why use resolution scaling?
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---------------------------
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With the ever-increasing rendering complexity of modern games, rendering at
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native resolution isn't always viable anymore, especially on lower-end GPUs.
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Resolution scaling is one of the most direct ways to influence the GPU
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requirements of a scene. In scenes that are bottlenecked by the GPU (rather than
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by the CPU), decreasing the resolution scale can improve performance
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significantly. Resolution scaling is particularly important on mobile GPUs where
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performance and power budgets are limited.
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While resolution scaling is an important tool to have, remember that resolution
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scaling is not intended to be a replacement for decreasing graphics settings on
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lower-end hardware. Consider exposing both resolution scale and graphics
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settings in your in-game menus.
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.. seealso::
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You can compare resolution scaling modes and factors in action using the
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`3D Antialiasing demo project <https://github.com/godotengine/godot-demo-projects/tree/master/3d/antialiasing>`__.
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.. note::
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Resolution scaling is currently not available for 2D rendering, but it can be
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simulated using the ``viewport`` stretch mode. See :ref:`doc_multiple_resolutions`
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for more information.
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Resolution scaling options
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--------------------------
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In the advanced Project Settings' **Rendering > Scaling 3D** section, you can
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find several options for 3D resolution scaling:
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Scaling mode
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~~~~~~~~~~~~
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- **Bilinear:** Standard bilinear filtering (default). This is used as a fallback
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when the current renderer doesn't support FSR 1.0 or FSR 2.2. *Available in
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all renderers.*
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- **FSR 1.0:** `AMD FidelityFX Super Resolution 1.0 <https://gpuopen.com/fidelityfx-superresolution/>`__.
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Slower, but higher quality compared to bilinear scaling. On very slow GPUs,
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the cost of FSR1 may be too expensive to be worth using it over bilinear
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scaling. *Only available when using the Forward+ renderer.*
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- **FSR 2.2:** AMD FidelityFX Super Resolution 2.2 (since Godot 4.2). Slowest,
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but even higher quality compared to FSR1 and bilinear scaling. On slow GPUs,
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the cost of FSR2 may be too expensive to be worth using it over bilinear
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scaling or FSR1. To match FSR2 performance with FSR1, you need to use a lower
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resolution scale factor. *Only available when using the Forward+ renderer.*
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Here are comparison images between native resolution, bilinear scaling with 50%
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resolution scale, FSR1, and FSR2 scaling with 50% resolution scale:
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.. image:: img/resolution_scaling_bilinear_0.5.png
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.. image:: img/resolution_scaling_fsr1_0.5.png
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.. image:: img/resolution_scaling_fsr2_0.5.webp
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FSR1 upscaling works best when coupled with another form of antialiasing.
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Temporal antialiasing (TAA) or multisample antialiasing (MSAA) should preferably
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be used in this case, as FXAA does not add temporal information and introduces
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more blurring to the image.
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On the other hand, FSR2 provides its own temporal antialiasing. This means you
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don't need to enable other antialiasing methods for the resulting image to look
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smooth. The **Use TAA** project setting is ignored when FSR2 is used as the 3D
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scaling method, since FSR2's temporal antialiasing takes priority.
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Here's the same comparison, but with 4× MSAA enabled on all images:
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.. image:: img/resolution_scaling_bilinear_msaa_4x_0.5.png
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.. image:: img/resolution_scaling_fsr1_msaa_4x_0.5.png
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.. image:: img/resolution_scaling_fsr2_msaa_4x_0.5.webp
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Notice how the edge upscaling of FSR1 becomes much more convincing once 4×
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MSAA is enabled. However, FSR2 doesn't benefit much from enabling MSAA since it
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already performs temporal antialiasing.
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Rendering scale
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~~~~~~~~~~~~~~~
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The **Rendering > Scaling 3D > Scale** setting adjusts the resolution scale.
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``1.0`` represents the full resolution scale, with the 3D rendering resolution
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matching the 2D rendering resolution. Resolution scales *below* ``1.0`` can be
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used to speed up rendering, at the cost of a blurrier final image and more aliasing.
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The rendering scale can be adjusted at runtime by changing the ``scaling_3d_scale``
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property on a :ref:`class_Viewport` node.
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Resolution scales *above* ``1.0`` can be used for supersample antialiasing
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(SSAA). This will provide antialiasing at a *very* high performance cost, and is
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**not recommended** for most use cases. See :ref:`doc_3d_antialiasing` for more
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information.
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The tables below list common screen resolutions, the resulting 3D rendering
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resolution and the number of megapixels that need to be rendered each frame
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depending on the rendering scale option. Rows are sorted from fastest to slowest
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in each table.
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.. note::
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The resolution scale is defined on a **per-axis** basis. For example, this
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means that halving the resolution scale factor will reduce the number of
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rendered megapixels per frame by a factor of 4, not 2. Therefore, very low
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or very high resolution scale factors can have a greater performance impact
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than expected.
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**1920×1080 (Full HD)**
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+--------------------------+-------------------------+-------------------------------+
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| Resolution scale factor | 3D rendering resolution | Megapixels rendered per frame |
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+==========================+=========================+===============================+
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| ``0.50`` | 960×540 | 0.52 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.67`` | 1286×723 | 0.93 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.75`` | 1440×810 | 1.17 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.85`` | 1632×918 | 1.50 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.00`` **(native)** | **1920×1080** | **2.07 MPix** |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.33`` (supersampling) | 2553×1436 | 3.67 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.50`` (supersampling) | 2880×1620 | 4.67 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``2.00`` (supersampling) | 3840×2160 | 8.29 MPix |
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+--------------------------+-------------------------+-------------------------------+
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**2560×1440 (QHD)**
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+--------------------------+-------------------------+-------------------------------+
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| Resolution scale factor | 3D rendering resolution | Megapixels rendered per frame |
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+==========================+=========================+===============================+
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| ``0.50`` | 1280×720 | 0.92 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.67`` | 1715×964 | 1.65 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.75`` | 1920×1080 | 2.07 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.85`` | 2176×1224 | 2.66 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.00`` **(native)** | **2560×1440** | **3.69 MPix** |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.33`` (supersampling) | 3404×1915 | 6.52 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.50`` (supersampling) | 3840×2160 | 8.29 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``2.00`` (supersampling) | 5120×2880 | 14.75 MPix |
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+--------------------------+-------------------------+-------------------------------+
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**3840×2160 (Ultra HD "4K")**
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+--------------------------+-------------------------+-------------------------------+
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| Resolution scale factor | 3D rendering resolution | Megapixels rendered per frame |
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+==========================+=========================+===============================+
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| ``0.50`` | 1920×1080 | 2.07 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.67`` | 2572×1447 | 3.72 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.75`` | 2880×1620 | 4.67 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``0.85`` | 3264×1836 | 5.99 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.00`` **(native)** | **3840×2160** | **8.29 MPix** |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.33`` (supersampling) | 5107×2872 | 14.67 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``1.50`` (supersampling) | 5760×3240 | 18.66 MPix |
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+--------------------------+-------------------------+-------------------------------+
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| ``2.00`` (supersampling) | 7680×4320 | 33.18 MPix |
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+--------------------------+-------------------------+-------------------------------+
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FSR Sharpness
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~~~~~~~~~~~~~
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*This is only available in the Forward+ renderer, not the Mobile or Compatibility
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renderers.*
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When using the FSR1 or FSR2 scaling modes, the sharpness can be controlled using the
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**Rendering > Scaling 3D > FSR Sharpness** advanced project setting.
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The intensity is inverted compared to most other sharpness sliders: *lower*
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values will result in a sharper final image, while *higher* values will *reduce*
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the impact of the sharpening filter. ``0.0`` is the sharpest, while ``2.0`` is
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the least sharp. The default value of ``0.2`` provides a balance between
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preserving the original image's sharpness and avoiding additional aliasing due
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to oversharpening.
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.. note::
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If you wish to use sharpening when rendering at native resolution, Godot
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currently doesn't allow using the sharpening component of FSR1 (RCAS)
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independently from the upscaling component (EASU).
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As a workaround, you can set the 3D rendering scale to ``0.99``, set the
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scaling mode to **FSR 1.0** then adjust FSR sharpness as needed. This allows
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using FSR1 while rendering at a near-native resolution.
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Alternatively, you can set the scaling mode to **FSR 2.2** with the 3D
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rendering scale set to ``1.0`` if you have enough GPU headroom. This also
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provides high-quality temporal antialiasing. The **FSR Sharpness** setting
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remains functional in this case.
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.. _doc_resolution_scaling_mipmap_bias:
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Mipmap bias
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~~~~~~~~~~~
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*This is only available in the Forward+ and Mobile renderers, not the Compatibility
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renderer.*
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Godot automatically uses a negative texture mipmap bias when the 3D resolution
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scale is set below ``1.0``. This allows for better preservation of texture
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detail at the cost of a grainy appearance on detailed textures.
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The texture LOD bias currently affects both 2D and 3D rendering in the same way.
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However, keep in mind it only has an effect on textures with mipmaps enabled.
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Textures used in 2D don't have mipmaps enabled by default, which means only 3D
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rendering is affected unless you enabled mipmaps on 2D textures in the Import
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dock.
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The formula used to determine the texture mipmap bias is:
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``log2f(min(scaling_3d_scale, 1.0)) + custom_texture_mipmap_bias``
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To counteract the blurriness added by some antialiasing methods, Godot also adds
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a ``-0.25`` offset when FXAA is enabled, and a ``-0.5`` offset when TAA is
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enabled. If both are enabled at the same time, a ``-0.75`` offset is used. This
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mipmap bias offset is applied *before* the resolution scaling offset, so it does
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not change depending on resolution scale.
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The texture LOD bias can manually be changed by adjusting the **Rendering >
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Textures > Default Filters > Texture Mipmap Bias** advanced project setting. It
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can also be changed at runtime on :ref:`Viewports <class_Viewport>` by
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adjusting the ``texture_mipmap_bias`` property.
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.. warning::
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Adjusting the mipmap LOD bias manually can be useful in certain scenarios,
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but this should be done carefully to prevent the final image from looking
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grainy in motion.
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*Negative* mipmap LOD bias can also decrease performance due to
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higher-resolution mips having to be sampled further away. Recommended values
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for a manual offset are between ``-0.5`` and ``0.0``.
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*Positive* mipmap LOD bias will make mipmapped textures appear blurrier than
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intended. This may improve performance slightly, but is otherwise not
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recommended as the loss in visual quality is usually not worth the
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performance gain.
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The example below shows an extreme case, with a mipmap LOD bias of ``-1.0`` and
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anisotropic filtering disabled to make the difference more noticeable:
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.. image:: img/resolution_scaling_texture_mipmap_bias_comparison.png
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Troubleshooting
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---------------
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Performance does not increase much when decreasing resolution scale
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If performance doesn't increase much when decreasing resolution scale to a value
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like ``0.5``, it likely means the performance bottleneck is elsewhere in your
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scene. For example, your scene could have too many draw calls, causing a CPU
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bottleneck to occur. Likewise, you may have too many graphics effects enabled
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for your GPU to handle (such as SDFGI, SSAO or SSR).
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See the :ref:`doc_performance` tutorials for more information.
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