renderer

The renderer system configures a scene's THREE.WebGLRenderer instance. It also configures presentation attributes when entering WebVR/WebXR.

Example

<a-scene renderer="antialias: true;
                   colorManagement: true;
                   sortTransparentObjects: true;
                   maxCanvasWidth: 1920;
                   maxCanvasHeight: 1920;"></a-scene>

Properties

NOTE: Once the scene is initialized, none of these properties may no longer be changed apart from "exposure", "toneMapping", "sortTransparentObjects" and "foveationLevel" which can be set dynamically.

antialias

When enabled, smooths jagged edges on curved lines and diagonals at moderate performance cost. By default, antialiasing is disabled on mobile devices.

colorManagement

Color management provides more accurate rendering and reduces the likelihood that scenes will appear overlit or "washed out." Enabling color management is recommended for precisely matching colors from texturing and modeling tools, but unofficial components may not always respond to color management properly at this time.

Managed and unmanaged color modes are similar to linear and gamma workflows, respectively, in other engines and tools.

NOTE: In three.js, and previous versions of A-Frame, a gammaOutput: true property was available. This is applied automatically when color management is enabled.

highRefreshRate

Switches to a higher frame rate than the default, for the given device.

This requires support for supportedFrameRates and updateTargetFrameRate as defined in the WebXR specs. Currently this is supported on the Oculus Browser, but is expected to be supported by other browsers in future.

Frame rates used are as follows:

foveationLevel

Controls the amount of foveation which renders fewer pixels near the edges of the user's field of view when in stereo rendering mode on certain systems. The value should be in the range of 0 to 1, where 0 is the minimum and 1 the maximum amount of foveation. This is currently supported by the Oculus Browser.

sortTransparentObjects

Sorting is used to attempt to properly render objects that have some degree of transparency. Due to various limitations, proper transparency often requires some amount of careful setup. By default, transparent objects are not sorted, and the order of elements in the DOM determines order of rendering. Re-ordering DOM elements provides one way of forcing a consistent behavior, whereas use of renderer="sortTransparentObjects: true" may cause unwanted changes as the camera moves.

Some more background on how A-Frame sorts objects for rendering can be found here

logarithmicDepthBuffer

A logarithmic depth buffer may provide better sorting and rendering in scenes containing very large differences of scale and distance.

Precision

Set precision in fragment shaders. Main use is to address issues in older hardware / drivers. Adreno 300 series GPU based phones are particularly problematic. You can set to mediump as a workaround. It will improve performance, in mobile in particular but be aware that might cause visual artifacts in shaders / textures.

alpha

Whether the canvas should contain an alpha buffer. If this is true the renderer will have a transparent backbuffer and the canvas can be composited with the rest of the webpage. See here for more info.

multiviewStereo

Performance improvement for applications that are CPU limited and draw count bound. Most experiences will get a free perf gain from this extension at not visual cost but there are limitations to consider. multiview builds on the multisampled render to texture extension that discards the frame buffer if there are other texture operations during rendering. Problem outlined in https://github.com/KhronosGroup/WebGL/issues/2912. Until browsers and drivers allow more control of when multisample is resolved we have a workaround with some drawbacks. As a temporary solution when enabling multiview the upload of texture data is deferred until the rendering of the main scene has ended, adding one extra frame of latency to texture uploads. Scenarios affected are for example skeletal meshes that upload bone textures with TexImage. With the workadound in place all bone animations will lag by one frame. Another issue is rendering mirror reflexions or rendering another view in the middle of the scene. The logic would have to move to the beginning of the frame to make sure it's not interrupted by the multiview frame. Because of the limitations this flag is disabled by default so developers can address any issues before enabling.